About NUTRIENTS
About nutrition
For nutrition in humans, see Human nutrition.
For nutrition in animals, see Animal nutrition.
For nutrition in plants, see Plant nutrition.
Nutrition is the
science that interprets the interaction of nutrients and
other substances in food in
relation to maintenance, growth, reproduction, health and disease of an
organism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and
excretion.[1]
The diet of
an organism is what it eats, which is largely determined by the availability,
the processing and palatability of foods. A healthy diet includes preparation of
food and storage methods that preserve nutrients from
oxidation, heat or leaching, and that reduce risk of foodborne
illness.
A poor diet can cause deficiency
diseases such as blindness, anemia, scurvy, preterm birth, stillbirth and cretinism;[2] health-threatening
conditions like obesity[3][4] and metabolic syndrome;[5] and such
common chronic systemic diseases as cardiovascular disease,[6] diabetes,[7][8] and osteoporosis.[9][10][11] A poor diet
can cause the wasting of kwashiorkor in
acute cases, and the stunting of marasmus in
chronic cases of malnutrition.[2]
The list of nutrients that people are
known to require is, in the words of Marion Nestle, "almost certainly
incomplete".[50] As of 2014, nutrients are
thought to be of two types: macro-nutrients which are needed in
relatively large amounts, and micronutrients which are needed in
smaller quantities.[51] A type of carbohydrate, dietary fiber, i.e. non-digestible material
such as cellulose, is required,[52] for both mechanical and
biochemical reasons, although the exact reasons remain unclear. Some nutrients
can be stored - the fat-soluble vitamins - while others are required more or
less continuously. Poor health can be caused by a lack of required nutrients,
or for some vitamins and minerals, too much of a required nutrient.
The macronutrients are carbohydrates, fiber, fats, protein, and water.[51] The macronutrients (excluding
fiber and water) provide structural material (amino acids from which proteins
are built, and lipids from which cell membranes and some
signaling molecules are built) and energy. Some of the structural material can be
used to generate energy internally, and in either case it is measured in Joules or kilocalories (often called
"Calories" and written with a capital C to
distinguish them from little 'c' calories). Carbohydrates and proteins provide
17 kJ approximately (4 kcal) of energy per gram, while fats provide
37 kJ (9 kcal) per gram,[53] though the net energy from
either depends on such factors as absorption and digestive effort, which vary
substantially from instance to instance. Vitamins, minerals, fiber, and water
do not provide energy, but are required for other reasons.
Molecules of carbohydrates and fats
consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from
simple monosaccharides (glucose,
fructose and galactose) to complex polysaccharides (starch). Fats are triglycerides, made of assorted fatty acid monomersbound to a glycerol backbone. Some fatty acids, but
not all, are essential in
the diet: they cannot be synthesized in the body. Protein molecules contain
nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental
components of protein are nitrogen-containing amino acids, some of which are essential in
the sense that humans cannot make them internally. Some of the amino acids are
convertible (with the expenditure of energy) to glucose and can be used for
energy production, just as ordinary glucose, in a process known as gluconeogenesis. By breaking down existing
protein, the carbon skeleton of the various amino acids can be metabolized to
intermediates in cellular respiration; the remaining ammonia is discarded
primarily as urea in urine.
Main article: Carbohydrate
Carbohydrates may be classified
as monosaccharides, disaccharides, or polysaccharides depending on the number
of monomer (sugar) units they contain. They constitute a large part of foods
such as rice, noodles, bread,
and other grain-based products, also potatoes, yams,
beans, fruits, fruit juices and vegetables. Monosaccharides, disaccharides, and
polysaccharides contain one, two, and three or more sugar units, respectively.
Polysaccharides are often referred to as complex carbohydrates
because they are typically long, multiple branched chains of sugar units.
Traditionally, simple carbohydrates
are believed to be absorbed quickly, and therefore to raise blood-glucose
levels more rapidly than complex carbohydrates. This, however, is not accurate.[54][55][56][57] Some simple carbohydrates
(e.g., fructose) follow different metabolic pathways (e.g., fructolysis) that result in only a
partial catabolism to
glucose, while, in essence, many complex carbohydrates may be digested at the
same rate as simple carbohydrates.[58] The World Health Organization
(WHO) recommends that added sugars should represent no more than 10% of total
energy intake.[59]
Main article: Dietary fiber
Dietary fiber is a carbohydrate that
is incompletely absorbed in humans and in some animals. Like all carbohydrates,
when it is metabolized it can produce four Calories (kilocalories) of energy
per gram. However, in most circumstances it accounts for less than that because
of its limited absorption and digestibility. Dietary fiber consists mainly of
cellulose, a large carbohydrate polymer which is indigestible as humans do not
have the required enzymes to disassemble it. There are two subcategories:
soluble and insoluble fiber. Whole grains, fruits (especially plums, prunes,
and figs), and vegetables are good sources of
dietary fiber. There are many health benefits of a high-fiber diet. Dietary
fiber helps reduce the chance of gastrointestinal problems such as constipation and diarrhea by increasing the weight and
size of stool and softening it. Insoluble fiber, found in whole wheat flour, nuts and vegetables,
especially stimulates peristalsis;– the
rhythmic muscular contractions of the intestines, which move digest along the
digestive tract. Soluble fiber, found in oats, peas, beans, and many fruits,
dissolves in water in the intestinal tract to produce a gel that slows the
movement of food through the intestines. This may help lower blood glucose
levels because it can slow the absorption of sugar. Additionally, fiber,
perhaps especially that from whole grains, is thought to possibly help lessen
insulin spikes, and therefore reduce the risk of type 2 diabetes. The link between increased
fiber consumption and a decreased risk of colorectal cancer is still uncertain.
Main article: Fat
A molecule of dietary fat typically
consists of several fatty acids (containing
long chains of carbon and hydrogen atoms), bonded to a glycerol. They are typically found as triglycerides (three fatty acids attached
to one glycerol backbone). Fats may be classified as saturated or unsaturated depending on the detailed
structure of the fatty acids involved. Saturated fats have all of the carbon
atoms in their fatty acid chains bonded to hydrogen atoms, whereas unsaturated
fats have some of these carbon atoms double-bonded, so their molecules have
relatively fewer hydrogen atoms than a saturated fatty acid of the same length.
Unsaturated fats may be further classified as monounsaturated (one double-bond)
or polyunsaturated (many double-bonds). Furthermore, depending on the location
of the double-bond in the fatty acid chain, unsaturated fatty acids are
classified as omega-3 or omega-6 fatty acids. Trans fats are a type of unsaturated fat
with trans-isomer bonds; these are rare in nature and in foods from
natural sources; they are typically created in an industrial process called
(partial) hydrogenation. There
are nine kilocalories in each gram of fat. Fatty acids such as conjugated
linoleic acid, catalpic acid, eleostearic acid and punicic acid, in addition to providing energy,
represent potent immune modulatory molecules.
Saturated fats (typically from animal
sources) have been a staple in many world cultures for millennia. Unsaturated
fats (e. g., vegetable oil) are considered healthier, while trans fats are to
be avoided. Saturated and some trans fats are typically solid at room
temperature (such as butter or lard),
while unsaturated fats are typically liquids (such as olive oil or flaxseed oil). Trans fats are very rare in
nature, and have been shown to be highly detrimental to human health, but have
properties useful in the food processing industry, such as
rancidity resistance.[60]
Main article: Essential fatty acids
Most fatty acids are non-essential,
meaning the body can produce them as needed, generally from other fatty acids
and always by expending energy to do so. However, in humans, at least two fatty
acids are essential and
must be included in the diet. An appropriate balance of essential fatty acids—omega-3 and omega-6 fatty acids—seems
also important for health, although definitive experimental demonstration has
been elusive. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for
a class of eicosanoidsknown
as prostaglandins,
which have roles throughout the human body. They are hormones, in some respects. The omega-3 eicosapentaenoic acid (EPA),
which can be made in the human body from the omega-3 essential fatty acid alpha-linolenic acid (ALA),
or taken in through marine food sources, serves as a building block for series
3 prostaglandins (e.g., weakly inflammatory PGE3). The omega-6
dihomo-gamma-linolenic acid (DGLA) serves as a building block for series 1
prostaglandins (e.g. anti-inflammatory PGE1), whereas arachidonic acid (AA)
serves as a building block for series 2 prostaglandins (e.g. pro-inflammatory
PGE 2). Both DGLA and AA can be made from the omega-6 linoleic acid (LA) in the human body, or
can be taken in directly through food. An appropriately balanced intake of
omega-3 and omega-6 partly determines the relative production of different
prostaglandins, which is one reason why a balance between omega-3 and omega-6
is believed important for cardiovascular health. In industrialized societies,
people typically consume large amounts of processed vegetable oils, which have
reduced amounts of the essential fatty acids along with too much of omega-6
fatty acids relative to omega-3 fatty acids.
The conversion rate of omega-6 DGLA
to AA largely determines the production of the prostaglandins PGE1 and PGE2.
Omega-3 EPA prevents AA from being released from membranes, thereby skewing
prostaglandin balance away from pro-inflammatory PGE2 (made from AA) toward
anti-inflammatory PGE1 (made from DGLA). Moreover, the conversion
(desaturation) of DGLA to AA is controlled by the enzyme delta-5-desaturase, which in turn is
controlled by hormones such as insulin (up-regulation) and glucagon (down-regulation). The amount
and type of carbohydrates consumed, along with some types of amino acid, can
influence processes involving insulin, glucagon, and other hormones; therefore,
the ratio of omega-3 versus omega-6 has wide effects on general health, and
specific effects on immune function and inflammation, and mitosis (i.e., cell division).
Proteins are chains
of amino acids found in most nutritional foods.
Main article: Protein (nutrient)
Proteins are structural materials in
much of the animal body (e.g. muscles, skin, and hair). They also form the
enzymes that control chemical reactions throughout the body. Each protein
molecule is composed of amino acids, which
are characterized by inclusion of nitrogen and sometimes sulphur (these
components are responsible for the distinctive smell of burning protein, such
as the keratin in hair). The body requires amino
acids to produce new proteins (protein retention) and to replace damaged
proteins (maintenance). As there is no protein or amino acid storage provision,
amino acids must be present in the diet. Excess amino acids are discarded,
typically in the urine. For all animals, some amino acids are essential (an
animal cannot produce them internally) and some are non-essential (the
animal can produce them from other nitrogen-containing compounds). About twenty
amino acids are found in the human body, and about ten of these are essential
and, therefore, must be included in the diet. A diet that contains adequate
amounts of amino acids (especially those that are essential) is particularly
important in some situations: during early development and maturation,
pregnancy, lactation, or injury (a burn, for instance). A complete protein
source contains all the essential amino acids; an incomplete protein
source lacks one or more of the essential amino acids.
It is possible with protein combinations of
two incomplete protein sources (e.g., rice and beans) to make a complete
protein source, and characteristic combinations are the basis of distinct
cultural cooking traditions. However, complementary sources of protein do not
need to be eaten at the same meal to be used together by the body.[61] Excess amino acids from protein
can be converted into glucose and used for fuel through a process called gluconeogenesis.
Main article: Drinking water
Water is excreted from the body in
multiple forms; including urine and feces, sweating, and by water vapour in the exhaled breath.
Therefore, it is necessary to adequately rehydrate to replace lost fluids.
Early recommendations for the quantity
of water required for maintenance of good health suggested that 6–8 glasses of
water daily is the minimum to maintain proper hydration.[62] However the notion that a
person should consume eight glasses of water per day cannot be traced to a
credible scientific source.[63] The original water intake
recommendation in 1945 by the Food and Nutrition Board of the National
Research Council read: "An ordinary standard for diverse
persons is 1 milliliter for each calorie of food. Most of this quantity is
contained in prepared foods."[64] More recent comparisons of
well-known recommendations on fluid intake have revealed large discrepancies in
the volumes of water we need to consume for good health.[65] Therefore, to help standardize
guidelines, recommendations for water consumption are included in two
recent European
Food Safety Authority (EFSA) documents (2010): (i) Food-based
dietary guidelines and (ii) Dietary reference values for water or adequate
daily intakes (ADI).[66] These specifications were
provided by calculating adequate intakes from measured intakes in populations
of individuals with “desirable osmolarity values of urine and desirable water
volumes per energy unit consumed.”[66]
For healthful hydration, the current
EFSA guidelines recommend total water intakes of 2.0 L/day for adult females
and 2.5 L/day for adult males. These reference values include water from
drinking water, other beverages, and from food. About 80% of our daily water
requirement comes from the beverages we drink, with the remaining 20% coming
from food.[67] Water content varies depending
on the type of food consumed, with fruit and vegetables containing more than
cereals, for example.[68] These values are estimated
using country-specific food balance sheets published by the Food and
Agriculture Organisation of the United Nations.[68]
The EFSA panel also determined
intakes for different populations. Recommended intake volumes in the elderly
are the same as for adults as despite lower energy consumption, the water
requirement of this group is increased due to a reduction in renal concentrating
capacity.[66] Pregnant and breastfeeding women require additional
fluids to stay hydrated. The EFSA panel proposes that pregnant women should
consume the same volume of water as non-pregnant women, plus an increase in
proportion to the higher energy requirement, equal to 300 mL/day.[66] To compensate for additional
fluid output, breastfeeding women require an additional 700 mL/day above the
recommended intake values for non-lactating women. Dehydration and
over-hydration - too little and too much water, respectively - can have harmful
consequences. Drinking too much water is one of the possible causes of hyponatremia, i.e., low serum sodium.[66][69]
Pure ethanol provides 7 calories per
gram. For spirits (vodka, gin, rum, etc.) a standard serving in the United
States is 1.5 fluid ounces, which at 40% ethanol (80 proof) would be 14 grams
and 98 calories. At 50% alcohol, 17.5 grams and 122.5 calories. Wine and beer
contain a similar range of ethanol for servings of 5 ounces and 12 ounces,
respectively, but these beverages also contain non-ethanol calories. A 5 ounce
serving of wine contains 100 to 130 calories. A 12 ounce serving of beer
contains 95 to 200 calories.[citation needed]According to the
U.S. Department of Agriculture, based on NHANES 2013-2014 surveys, women ages 20
and up consume on average 6.8 grams/day and men consume on average 15.5
grams/day.[70] Ignoring the non-alcohol
contribution of those beverages, the average ethanol calorie contributions are
48 and 108 cal/day. Alcoholic beverages are considered empty calorie foods because other than
calories, these contributes no essential nutrients.
Main articles: Mineral (nutrient) and Composition
of the human body
Dietary minerals are inorganic chemical elements required by living
organisms,[71] other than the four
elements carbon, hydrogen, nitrogen, and oxygen that are present in nearly
all organic molecules.
The term "mineral" is archaic, since the intent is to describe simply
the less common elements in the diet. Some are heavier than the four just
mentioned, including several metals, which often occur as
ions in the body. Some dietitians recommend that these be supplied from foods
in which they occur naturally, or at least as complex compounds, or sometimes
even from natural inorganic sources (such as calcium carbonate from ground oyster shells). Some minerals are absorbed
much more readily in the ionic forms found in such sources. On the other hand,
minerals are often artificially added to the diet as supplements; the most
famous is likely iodine in iodized salt which prevents goiter.
Many elements are essential in
relative quantity; they are usually called "bulk minerals". Some are
structural, but many play a role as electrolytes.[72] Elements with recommended
dietary allowance (RDA)
greater than 150 mg/day are, in alphabetical order (with informal or
folk-medicine perspectives in parentheses):
·
Calcium, a common electrolyte, but also needed
structurally (for muscle and digestive system health, bone strength, some forms
neutralize acidity, may help clear toxins, provides signaling ions for nerve
and membrane functions)
·
Magnesium, required for processing ATP and
related reactions (builds bone, causes strong peristalsis, increases
flexibility, increases alkalinity)
·
Potassium, a very common electrolyte (heart
and nerve health)
·
Sodium, a very common electrolyte; in general
not found in dietary supplements, despite being needed in large quantities,
because the ion is very common in food: typically as sodium chloride, or common salt. Excessive
sodium consumption can deplete calcium and magnesium,[verification needed] leading to
high blood pressure and osteoporosis.
·
Sulfur, for three essential amino acids and
therefore many proteins (skin, hair, nails, liver, and pancreas). Sulfur is not
consumed alone, but in the form of sulfur-containing amino acids
Many elements are required in trace
amounts, usually because they play a catalytic role in enzymes.[74] Some trace mineral elements
(RDA < 200 mg/day) are, in alphabetical order:
·
Cobalt required for biosynthesis of vitamin B12 family of coenzymes. Animals cannot biosynthesize B12,
and must obtain this cobalt-containing vitamin in their diet.
·
Copper required component of many redox
enzymes, including cytochrome c oxidase
Main article: Copper in health
·
Chromium required for sugar metabolism
·
Iodine required not only for the
biosynthesis of thyroxine but
also — it is presumed — for other important organs as breast,
stomach, salivary glands, thymus, etc. (see Extrathyroidal iodine); for this reason iodine is needed in
larger quantities than others in this list, and sometimes classified with the
macrominerals
·
Iron required for many enzymes, and
for hemoglobin and some other proteins
·
Manganese (processing of oxygen)
·
Molybdenum required for xanthine oxidase and related oxidases
·
Selenium required for peroxidase (antioxidant proteins)
·
Zinc required for several enzymes such
as carboxypeptidase, liver alcohol
dehydrogenase, and carbonic anhydrase
Main article: Vitamin
Vitamins are essential nutrients,[71] necessary in the diet for good
health. (Vitamin D is an exception, as it can be
synthesized in the skin in the presence of UVB radiation, and many animal species can
synthesize vitamin C.) Vitamin deficiencies may result in disease conditions,
including goitre, scurvy, osteoporosis, impaired immune system,
disorders of cell metabolism, certain forms of cancer, symptoms of premature
aging, and poor psychological health,
among many others.[75] Excess levels of some vitamins
are also dangerous to health. The Food and Nutrition Board of the Institute of
Medicine has established Tolerable Upper Intake Levels (ULs) for seven
vitamins.[76]
Main article: Healthy diet
T. Colin Campbell is among the scientists
who advocate a plant-based diet
Heart disease, cancer, obesity, and
diabetes are commonly called "Western" diseases because these
maladies were once rarely seen in developing countries. An international study in China found
some regions had virtually no cancer or heart disease, while in other areas
they reflected "up to a 100-fold increase" coincident with shifts
from diets that were found to be entirely plant-based to heavily animal-based,
respectively.[77] In contrast, diseases of
affluence like cancer and heart disease are common throughout the developed
world, including the United States. Adjusted for age and exercise, large
regional clusters of people in China rarely suffered from these "Western"
diseases possibly because their diets are rich in vegetables, fruits, and whole
grains, and have little dairy and meat products.[77] There are arguments for and against this
controversial issue.
Main article: French paradox
The French paradox was an observation
from the 1980s that the French suffer a relatively low incidence of coronary
heart disease, despite having a diet relatively rich in saturated fats. A
number of explanations were suggested:
·
Compared to U.S., less consumption of processed carbohydrate and other
junk foods, and more consumption of fruits, vegetables, whole grains and fish.[79]
·
Compared to U.S., lower consumption of artificially produced trans-fats,
which has been shown to have greater cholesterol raising effects than saturated
fat.[81]
However, statistics collected by
the World Health
Organization from 1990–2000 show that the incidence of heart
disease in France may have been underestimated and, in fact, may be similar to
that of neighboring countries.[82]
Main article: Phytochemical
See also: List of
antioxidants in food
Phytochemicals such as polyphenols are compounds produced
naturally in plants (phyto means "plant" in Greek). In general, the
term is used to refer to those chemicals under research to assess whether they
have biological significance. To date, there is no evidence in humans that
polyphenols or other non-nutrient compounds from plants have health effects.[83]
While initial studies sought to
reveal if nutrient antioxidant supplements might promote health, one meta-analysis
concluded that supplementation with vitamins A and E and beta-carotene did not
convey any benefits and may in fact increase risk of death. Vitamin C and
selenium supplements did not impact mortality rate. Health effects of
non-nutrient phytochemicals such as polyphenols were not assessed.[84][85]
Colorful fruits and
vegetables can be components of a healthy diet.
Main article: Gut flora
Animal intestines contain a large
population of gut flora. In humans,
the four dominant phyla are Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria.[86] They are essential to digestion and are also affected by food
that is consumed. Bacteria in the large intestine perform many important
functions for humans, including breaking down and aiding in the absorption of
soluble fiber, stimulating cell growth, repressing the growth of harmful bacteria,
training the immune system to respond only to pathogens, producing vitamin B12, and defending against some infectious
diseases.[87] "Probiotics" refers to the idea of
deliberately consuming live bacteria in an attempt to change the bacterial
population in the large intestine, to the health benefit of the host human or
animal. "Prebiotic (nutrition)"
refers to the idea that consuming a bacterial energy source such as soluble
fiber could support the population of health-beneficial bacteria in the large
intestine. There is not yet a scientific consensus as to health benefits
accruing from probiotics or prebiotics.
Main articles: Animal nutrition and Human nutrition
Carnivore and herbivore diets are contrasting, with
basic nitrogen and carbon proportions vary for their
particular foods. Many herbivores rely on bacterial fermentation to create
digestible nutrients from indigestible plant cellulose, while obligate
carnivores must eat animal meats to obtain certain vitamins or nutrients their
bodies cannot otherwise synthesize.[88]
Main article: Plant nutrition
Plant nutrition is the study of
the chemical elements that
are necessary for plant growth.[89] There are several principles
that apply to plant nutrition. Some elements are directly involved in
plant metabolism. However, this principle does not
account for the so-called beneficial elements, whose presence, while not
required, has clear positive effects on plant growth.
A nutrient that is able to limit
plant growth according to Liebig's law of
the minimum is considered an essential plant nutrient if the
plant cannot complete its full life cycle without it. There are 16 essential
plant soil nutrients, besides the three major elemental nutrients carbon and
oxygen that are obtained by photosynthetic plants from carbon dioxide in air,
and hydrogen, which is obtained from water.
Plants uptake essential elements from
the soil through their roots and
from the air (consisting of mainly nitrogen and oxygen) through their leaves.
Green plants obtain their carbohydrate supply from the carbon dioxide in the
air by the process of photosynthesis. Carbon and oxygen are absorbed
from the air, while other nutrients are absorbed from the soil. Nutrient uptake
in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions (H+) into the soil
through proton pumps. These
hydrogen ions displace cationsattached to
negatively charged soil particles so that the cations are available for uptake
by the root. In the leaves, stomata open to take
in carbon dioxide and expel oxygen. The carbon dioxide
molecules are used as the carbon source in photosynthesis.
Although nitrogen is plentiful in the Earth's
atmosphere, very few plants can use this directly. Most plants, therefore, require
nitrogen compounds to be present in the soil in which they grow. This is made
possible by the fact that largely inert atmospheric nitrogen is changed in
a nitrogen fixation process
to biologically usable forms in the soil by bacteria.[90]
Plant nutrition is a difficult
subject to understand completely, partially because of the variation between
different plants and even between different species or individuals of a
given clone. Elements present at low levels may
cause deficiency symptoms, and toxicity is possible at levels that are too
high. Furthermore, deficiency of one element may present as symptoms of
toxicity from another element, and vice versa.
Canada's Food Guide is
another example government-run nutrition program. Produced by Health Canada, the guide advises food
quantities, provides education on balanced nutrition, and promotes physical
activity in accordance with government-mandated nutrient needs. Like other
nutrition programs around the world, Canada's Food Guide divides nutrition into
four main food groups: vegetables and fruit, grain products, milk and
alternatives, and meat and alternatives.[91] It is interesting to note that,
unlike its American counterpart, the Canadian guide references and provides
alternative to meat and dairy, which can be attributed to the growing vegan and vegetarian movements.
In the US, nutritional standards and
recommendations are established jointly by the US
Department of Agriculture and US Department of Health and Human Services.
Dietary and physical activity guidelines from the USDA are presented in the
concept of MyPlate, which superseded the food pyramid, which replaced the Four Food Groups. The Senate committee
currently responsible for oversight of the USDA is the Agriculture,
Nutrition and Forestry Committee. Committee hearings are often televised on C-SPAN. The U.S.
Department of Health and Human Services provides a sample
week-long menu that fulfills the nutritional recommendations of the government.[92]
Governmental organisations have been
working on nutrition literacy interventions in non-primary health care settings
to address the nutrition information problem in the U.S. Some programs include:
The Family Nutrition Program (FNP) is
a free nutrition education program serving low-income adults around the U.S.
This program is funded by the Food Nutrition Service’s (FNS) branch of the
United States Department of Agriculture (USDA) usually through a local state
academic institution that runs the program. The FNP has developed a series of
tools to help families participating in the Food Stamp Program stretch their
food dollar and form healthful eating habits including nutrition education.[citation needed]
Expanded Food and Nutrition Education Program (ENFEP)
is a unique program that currently operates in all 50 states and in American
Samoa, Guam, Micronesia, Northern Marianas, Puerto Rico, and the Virgin
Islands. It is designed to assist limited-resource audiences in acquiring the
knowledge, skills, attitudes, and changed behavior necessary for nutritionally
sound diets, and to contribute to their personal development and the
improvement of the total family diet and nutritional well-being.
An example of a state initiative to
promote nutrition literacy is Smart
Bodies, a public-private partnership between the state’s largest
university system and largest health insurer, Louisiana State Agricultural
Center and Blue Cross and Blue Shield of Louisiana Foundation. Launched in
2005, this program promotes lifelong healthful eating patterns and physically
active lifestyles for children and their families. It is an interactive
educational program designed to help prevent childhood obesity through
classroom activities that teach children healthful eating habits and physical
exercise.
Nutrition is taught in schools in many countries.
In England and Wales,
the Personal and
Social Education and Food Technology curricula include
nutrition, stressing the importance of a balanced diet and teaching how to read
nutrition labels on packaging. In many schools, a Nutrition class will fall
within the Family and Consumer Science or Health departments. In some American
schools, students are required to take a certain number of FCS or Health
related classes. Nutrition is offered at many schools, and, if it is not a
class of its own, nutrition is included in other FCS or Health classes such as:
Life Skills, Independent Living, Single Survival, Freshmen Connection, Health
etc. In many Nutrition classes, students learn about the food groups, the food
pyramid, Daily Recommended Allowances, calories, vitamins, minerals,
malnutrition, physical activity, healthful food choices, portion sizes, and how
to live a healthy life.
A 1985, US National
Research Council report entitled Nutrition Education in
US Medical Schools concluded that nutrition education in medical
schools was inadequate.[93] Only 20% of the schools
surveyed taught nutrition as a separate, required course. A 2006 survey found
that this number had risen to 30%.[94] Membership by physicians in
leading professional nutrition societies such as the American
Society for Nutrition has generally declined from the 1990s.[95]
In the US, Registered dietitian nutritionists (RDs
or RDNs)[96] are health professionals qualified
to provide safe, evidence-based dietary advice which includes a review of what
is eaten, a thorough review of nutritional health, and a personalized
nutritional treatment plan. They also provide preventive and therapeutic
programs at work places, schools and similar institutions. Certified
Clinical Nutritionists or
CCNs, are trained health professionals who also offer dietary advice on the
role of nutrition in chronic disease, including possible prevention or
remediation by addressing nutritional deficiencies before resorting to drugs.[97] Government regulation
especially in terms of licensing, is currently less universal for the CCN than
that of RD or RDN. Another advanced Nutrition Professional is a Certified
Nutrition Specialist or CNS. These Board Certified Nutritionists typically
specialize in obesity and chronic disease. In order to become board
certified, potential CNS candidate must pass an examination, much like
Registered Dieticians. This exam covers specific domains within the health
sphere including; Clinical Intervention and Human Health.[98]
The findings of the 2003 National
Assessment of Adult Literacy (NAAL) provide a basis upon which to frame the
nutrition literacy problem in the U.S. NAAL introduced the first ever measure
of "the degree to which individuals have the capacity to obtain, process
and understand basic health information and services needed to make appropriate
health decisions" – an objective of Healthy People 2010[99] and of which nutrition literacy
might be considered an important subset. On a scale of below basic, basic,
intermediate and proficient, NAAL found 13 percent of adult Americans have
proficient health literacy, 44% have intermediate literacy, 29 percent have
basic literacy and 14 percent have below basic health literacy. The study found
that health literacy increases with education and people living below the level
of poverty have lower health literacy than those above it.
Another study examining the health
and nutrition literacy status of residents of the lower Mississippi Delta found
that 52 percent of participants had a high likelihood of limited literacy
skills.[100] While a precise comparison
between the NAAL and Delta studies is difficult, primarily because of
methodological differences, Zoellner et al. suggest that health literacy rates
in the Mississippi Delta region are different from the U.S. general population
and that they help establish the scope of the problem of health literacy among
adults in the Delta region. For example, only 12 percent of study participants
identified the My Pyramid graphic two years after it had been launched by the
USDA. The study also found significant relationships between nutrition literacy
and income level and nutrition literacy and educational attainment[100] further delineating priorities
for the region.
These statistics point to the
complexities surrounding the lack of health/nutrition literacy and reveal the
degree to which they are embedded in the social structure and interconnected
with other problems. Among these problems are the lack of information about
food choices, a lack of understanding of nutritional information and its
application to individual circumstances, limited or difficult access to
healthful foods, and a range of cultural influences and socioeconomic
constraints such as low levels of education and high levels of poverty that
decrease opportunities for healthful eating and living.
The links between low health literacy
and poor health outcomes has been widely documented[101] and there is evidence that some
interventions to improve health literacy have produced successful results in
the primary care setting. More must be done to further our understanding of
nutrition literacy specific interventions in non-primary care settings[100] in order to achieve better
health outcomes.
Main article: Malnutrition
Malnutrition refers to insufficient,
excessive, or imbalanced consumption of nutrients by an organism. In developed
countries, the diseases of malnutrition are most often associated with
nutritional imbalances or excessive consumption. In developing countries,
malnutrition is more likely to be caused by poor access to a range of
nutritious foods or inadequate knowledge. In Mali the International Crops Research Institute for the Semi-Arid
Tropics (ICRISAT) and the Aga Khan Foundation,
trained women's groups to make equinut, a healthy and nutritional
version of the traditional recipe di-dèguè (comprising peanut
paste, honey and millet or rice flour). The aim was to boost nutrition and
livelihoods by producing a product that women could make and sell, and which
would be accepted by the local community because of its local heritage.[102]
Although under- and over-nutrition
are often viewed as human problems, pet animals can be under- or overfed by
their owners, domesticated animals can be undernourished for macro- and
micro-nutrients, affecting growth and health, and wild animals can be undernourished
to the point of starvation and death.
Nutritionism is the view that excessive
reliance on food science and the study of nutrition can lead to poor nutrition
and to ill health. It was originally credited to Gyorgy
Scrinis,[103] and was popularized by Michael Pollan. Since nutrients are invisible,
policy makers rely on nutrition experts to advise on food choices. Because
science has an incomplete understanding of how food affects the human body,
Pollan argues, nutritionism can be blamed for many of the health problems
relating to diet in the Western World today.[104][105]
The U.S. Food and Nutrition Board
sets Estimated Average Requirements (EARs) and Recommended Dietary Allowances
(RDAs) for vitamins and minerals. EARs and RDAs are part of Dietary Reference
Intakes.[106] The DRI documents describe
nutrient deficiency signs and symptoms.
The U.S. Food and Nutrition Board
sets Tolerable Upper Intake Levels (known as ULs) for vitamins and minerals
when evidence is sufficient. ULs are set a safe fraction below amounts shown to
cause health problems. ULs are part of Dietary Reference
Intakes.[107] The European
Food Safety Authority also reviews the same safety questions
and set its own ULs.[108]
When too much of one or more
nutrients is present in the diet to the exclusion of the proper amount of other
nutrients, the diet is said to be unbalanced. High calorie food ingredients
such as vegetable oils and sugar, and also alcohol, are referred to as "empty
calories" because they displace from the diet foods that also contain
protein, vitamins, minerals and fiber.[citation needed]
|
Nutrients
|
Deficiency
|
Excess
|
|
Low energy levels.
|
||
|
Micronutrient deficiency
|
Obesity, cardiovascular
disease (high glycemic index foods)
|
|
|
Low testosterone levels, vitamin
deficiencies.
|
||
|
None
|
||
|
Fat-soluble vitamin deficiency
|
||
|
Hypervitaminosis A (cirrhosis,
hair loss)
|
||
|
?
|
||
|
Skin and corneal lesions
|
?
|
|
|
Dyspepsia, cardiac arrhythmias,
birth defects
|
||
|
?
|
||
|
Diarrhea causing dehydration
|
||
|
Hypervitaminosis D (dehydration,
vomiting, constipation)
|
||
|
Neurological disease
|
Hypervitaminosis E (anticoagulant:
excessive bleeding)
|
|
|
Liver damage
|
||
|
Bleeding, Hemorrhages, Hemorrhagic stroke,
reduced glycemic control among diabetics
|
||
|
None
|
||
|
None
|
||
|
Weakness, nausea, vomiting,
impaired breathing, and hypotension
|
||
|
Iodine toxicity (goiter,
hypothyroidism)
|
||
Main article: Nootropic
Research indicates that improving the
awareness of nutritious meal choices and establishing long-term habits of
healthy eating have a positive effect on cognitive and spatial memory capacity,
with potential to increase a student's ability to process and retain academic
information.
Some organizations have begun working
with teachers, policymakers, and managed foodservice contractors to mandate
improved nutritional content and increased nutritional resources in school
cafeterias from primary to university level institutions. Health and nutrition
have been proven to have close links with overall educational success.[109] Currently, less than 10% of
American college students report that they eat the recommended five servings of
fruit and vegetables daily.[110] Better nutrition has been shown
to affect both cognitive and spatial memory performance; a study showed those
with higher blood sugar levels performed better on certain memory tests.[111] In another study, those who
consumed yogurt performed better on thinking tasks when compared to those that
consumed caffeine-free diet soda or confections.[112] Nutritional deficiencies have
been shown to have a negative effect on learning behavior in mice as far back
as 1951.[113]
"Better learning performance is
associated with diet-induced effects on learning and memory ability".[114]
The "nutrition-learning
nexus" demonstrates the correlation between diet and learning and has
application in a higher education setting.
"We find that better-nourished
children perform significantly better in school, partly because they enter
school earlier and thus have more time to learn but mostly because of greater
learning productivity per year of schooling."[115]
91% of college students feel that
they are in good health, whereas only 7% eat their recommended daily allowance
of fruits and vegetables.[110]
More "engaged" learning
models that encompass nutrition is an idea that is picking up steam at all
levels of the learning cycle.[118]
There is limited
research available that directly links a student's Grade Point Average (G.P.A.)
to their overall nutritional health. Additional substantive data is needed to
prove that overall intellectual health is closely linked to a person's diet, rather
than just another correlation fallacy.
Nutritional
supplement treatment may be appropriate for major depression, bipolar disorder, schizophrenia, and obsessive
compulsive disorder, the four most common mental disorders in
developed countries.[119] Supplements that have been
studied most for mood elevation and stabilization include eicosapentaenoic acid and docosahexaenoic acid (each
of which an omega-3 fatty acid contained
in fish oil but not in flaxseed oil), vitamin B12, folic acid, and inositol.[citation needed]
Cancer is now
common in developing countries. According to a study by the International
Agency for Research on Cancer, "In the developing world,
cancers of the liver, stomach and esophagus were more common, often linked to
consumption of carcinogenic preserved foods, such as smoked or salted food, and
parasitic infections that attack organs." Developed countries "tended
to have cancers linked to affluence or a 'Western lifestyle' — cancers of the
colon, rectum, breast and prostate — that can be caused by obesity, lack
of exercise, diet and age."[120]
Several lines of
evidence indicate lifestyle-induced hyperinsulinemia and reduced insulin
function (i.e., insulin resistance)
as a decisive factor in many disease states. For example, hyperinsulinemia and
insulin resistance are strongly linked to chronic inflammation, which in turn
is strongly linked to a variety of adverse developments such as arterial
microinjuries and clot formation (i.e., heart disease) and
exaggerated cell division (i.e., cancer). Hyperinsulinemia and insulin
resistance (the so-called metabolic syndrome)
are characterized by a combination of abdominal obesity, elevated blood sugar, elevated blood pressure, elevated blood triglycerides, and reduced HDL cholesterol. The negative effect of hyperinsulinemia
on prostaglandin PGE1/PGE2 balance may be significant.
The state of obesity clearly contributes to insulin
resistance, which in turn can cause type 2 diabetes. Virtually all obese and most
type 2 diabetic individuals have marked insulin resistance. Although the
association between overweight and insulin resistance is clear, the exact
(likely multifarious) causes of insulin resistance remain less clear. It is
important to note that it has been demonstrated that appropriate exercise, more
regular food intake, and reducing glycemic load (see below) all can reverse
insulin resistance in overweight individuals (and thereby lower blood sugar
levels in those with type 2 diabetes).
Obesity can
unfavourably alter hormonal and metabolic status via resistance to the
hormone leptin, and a vicious cycle may occur in which
insulin/leptin resistance and obesity aggravate one another. The vicious cycle
is putatively fuelled by continuously high insulin/leptin stimulation and fat
storage, as a result of high intake of strongly insulin/leptin stimulating
foods and energy. Both insulin and leptin normally function as satiety signals
to the hypothalamus in
the brain; however, insulin/leptin resistance may reduce this signal and
therefore allow continued overfeeding despite large body fat stores. In
addition, reduced leptin signalling to the brain may reduce leptin's normal
effect to maintain an appropriately high metabolic rate.
There is a debate
about how and to what extent different dietary factors— such as intake of
processed carbohydrates, total protein, fat, and carbohydrate intake, intake of
saturated and trans fatty acids, and low intake of vitamins/minerals—contribute
to the development of insulin and leptin resistance. In any case, analogous to
the way modern man-made pollution may possess the potential to overwhelm the
environment's ability to maintain homeostasis, the recent explosive introduction
of high glycemic index and
processed foods into the human diet may possess the potential to overwhelm the
body's ability to maintain homeostasis and health (as evidenced by the
metabolic syndrome epidemic).
Main article: Antinutrient
Antinutrients are
natural or synthetic compounds that interfere with the absorption of nutrients.
Nutrition studies focus on antinutrients commonly found in food sources and
beverages.
Sugar consumption
in the United States
The relatively
recent increased consumption of sugar has been linked to the rise of some
afflictions such as diabetes, obesity, and more recently heart disease.
Increased consumption of sugar has been tied to these three, among others.
Obesity levels have more than doubled in the last 30 years among adults, going
from 15% to 35% in the United States.[121] Obesity and diet also happen to
be high risk factors for diabetes. In the same time span that obesity doubled,
diabetes numbers quadrupled in America. Increased weight, especially in the
form of belly fat, and high sugar intake are also high risk factors for heart
disease.[122] Both sugar intake and fatty
tissue increase the probability of elevated LDL cholesterol in the bloodstream.
Elevated amounts of Low-density lipoprotein (LDL) cholesterol, is the primary
factor in heart disease. In order to avoid all the dangers of sugar, moderate
consumption is paramount.
Main article: Food processing
Since the Industrial Revolution some
two hundred years ago, the food processing industry has invented many technologies that both help keep foods
fresh longer and alter the fresh state of food as they appear in nature.
Cooling is the primary technology used to maintain freshness, whereas many more
technologies have been invented to allow foods to last longer without becoming
spoiled. These latter technologies include pasteurisation, autoclavation, drying, salting, and separation of various components,
all of which appearing to alter the original nutritional contents of food.
Pasteurisation and autoclavation (heating techniques) have no doubt improved
the safety of many common foods, preventing epidemics of bacterial infection.
But some of the (new) food processing technologies have downfalls as well.
Modern separation
techniques such as milling, centrifugation, and pressing have enabled concentration of
particular components of food, yielding flour, oils, juices, and so on, and
even separate fatty acids, amino acids, vitamins, and minerals. Inevitably,
such large-scale concentration changes the nutritional content of food, saving
certain nutrients while removing others. Heating techniques may also reduce
food's content of many heat-labile nutrients such as certain vitamins and
phytochemicals, and possibly other yet-to-be-discovered substances.[123] Because of reduced nutritional
value, processed foods are often 'enriched' or 'fortified' with some of the
most critical nutrients (usually certain vitamins) that were lost during
processing. Nonetheless, processed foods tend to have an inferior nutritional
profile compared to whole, fresh foods, regarding content of both sugar and
high GI starches, potassium/sodium, vitamins, fiber, and of intact,
unoxidized (essential) fatty acids. In addition, processed foods often contain
potentially harmful substances such as oxidized fats and trans fatty acids.
A dramatic example
of the effect of food processing on a population's health is the history of
epidemics of beri-beri in people
subsisting on polished rice. Removing the outer layer of rice by polishing it
removes with it the essential vitamin thiamine, causing beri-beri. Another example
is the development of scurvy among infants
in the late 19th century in the United States. It turned out that the vast
majority of sufferers were being fed milk that had been heat-treated (as
suggested by Pasteur) to
control bacterial disease. Pasteurisation was effective against bacteria, but
it destroyed the vitamin C.
As mentioned,
lifestyle- and obesity-related diseases are becoming increasingly prevalent all
around the world. There is little doubt that the increasingly widespread
application of some modern food processing technologies has contributed to this
development. The food processing industry is a major part of modern economy,
and as such it is influential in political decisions (e.g., nutritional
recommendations, agricultural subsidising). In any known profit-driven economy,
health considerations are hardly a priority; effective production of cheap
foods with a long shelf-life is more the trend. In general, whole, fresh foods
have a relatively short shelf-life and are less profitable to produce and sell
than are more processed foods. Thus, the consumer is left with the choice
between more expensive, but nutritionally superior, whole, fresh foods, and
cheap, usually nutritionally inferior, processed foods. Because processed foods
are often cheaper, more convenient (in both purchasing, storage, and
preparation), and more available, the consumption of nutritionally inferior
foods has been increasing throughout the world along with many
nutrition-related health complications.
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