Human nutrition

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Human nutrition deals with the provision of

The seven major classes of nutrients are carbohydrates,

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 also 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,^[5] 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,^[6] and water do not provide energy, but are required for other reasons. A third class of dietary material, fiber (i.e., nondigestible material such as cellulose), seems also to be required, for both mechanical and biochemical reasons, though the exact reasons remain unclear. For all age groups, males on average need to consume higher amounts of macronutrients than females. In general, intakes increase with age until the second or third decade of life.^[7]

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. Essential nutrients cannot be synthesized by the body, and must be obtained from food.

Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple

The list of nutrients that people are known to require is, in the words of Marion Nestle, "almost certainly incomplete".^[9]

Carbohydrates

Carbohydrates may be classified as

Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Monosaccharides include glucose, fructose and galactose.^[14] Disaccharides include sucrose, lactose, and maltose; purified sucrose, for instance, is used as table sugar.^[15] Polysaccharides, which include starch and glycogen, are often referred to as 'complex' carbohydrates because they are typically long multiple-branched chains of sugar units.

Traditionally, simple carbohydrates were believed to be absorbed quickly, and therefore raise blood-glucose levels more rapidly than complex carbohydrates. This is inaccurate.^{[16][17][18][19]} 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.^[20] The World Health Organization recommends that added sugars should represent no more than 10% of total energy intake.^[21]

The most common plant carbohydrate nutrient – starch – varies in its absorption. Starches have been classified as rapidly digestible starch, slowly digestible starch and resistant starch.^[22] Starches in plants are resistant to digestion (resistant starch), but cooking the starch in the presence of water can break down the starch granule and releases the glucose chains, making them more easily digestible by human digestive enzymes.^[23] Historically, food was less processed and starches were contained within the food matrix, making them less digestible.^[24] Modern food processing has shifted carbohydrate consumption from less digestible and resistant starch to much more rapidly digestible starch.^[25][26] For instance, the resistant starch content of a traditional African diet was 38 grams/day.^[27] The resistant starch consumption from countries with high starch intakes has been estimated to be 30-40 grams/day.^[28] In contrast, the average consumption of resistant starch in the United States was estimated to be 4.9 grams/day (range 2.8-7.9 grams of resistant starch/day).^[29]

Fat

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A molecule of dietary fat typically consists of several

Essential fatty acids

Main article:

Essential fatty acids

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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

Dietary fiber is a carbohydrate, specifically a polysaccharide, which 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, but in most circumstances, it accounts for less than that because of its limited absorption and digestibility.

The two subcategories are insoluble and soluble fiber.

Insoluble dietary fiber

Includes cellulose, a large carbohydrate polymer that is indigestible by humans, because humans do not have the required enzymes to break it down, and the human digestive system does not harbor enough of the types of microbes that can do so.

Includes resistant starch, an insoluble starch that resists digestion either because it is protected by a shell or food matrix (Type 1 resistant starch, RS1), maintains the natural starch granule (Type 2 resistant starch, RS2), is retrograded and partially crystallized (Type 3 resistant starch, RS3), has been chemically modified (Type 4 resistant starch, RS4) or has complexed with a lipid (Type 5 resistant starch, RS5).^[25] Natural sources of resistant starch (RS1, RS2 and RS3) are fermented by the microbes in the human digestive system to produce short-chain fatty acids which are utilized as food for the colonic cells or absorbed.^[25]

Soluble dietary fiber

Comprises a variety of

esters, and other carbohydrates that dissolve or gelatinize in water. Many of these soluble fibers can be fermented or partially fermented by microbes in the human digestive system to produce short-chain fatty acids which are absorbed and therefore introduce some caloric content.^[31]

In 2016, the U.S. FDA approved a qualified health claim stating that resistant starch might reduce the risk of type 2 diabetes, but with qualifying language for product labels that only limited scientific evidence exists to support this claim. The FDA requires specific labeling language, such as the guideline concerning resistant starch: "High-amylose maize resistant starch may reduce the risk of type 2 diabetes. FDA has concluded that there is limited scientific evidence for this claim."^[35]

Amino acids

Proteins are the basis of many animal body structures (e.g. muscles, skin, and hair) and form the

There is an ongoing debate about the differences in nutritional quality and adequacy of protein from vegan, vegetarian and animal sources, though many studies and institutions have found that a well-planned vegan or vegetarian diet contains enough high-quality protein to support the protein requirements of both sedentary and active people at all stages of life.^{[38][39][40][41]}

Water

Water is excreted from the body in multiple forms; including

Early recommendations for the quantity of water required for maintenance of good health suggested that six to eight glasses of water daily is the minimum to maintain proper

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.[47] Water content varies depending on the type of food consumed, with fruit and vegetables containing more than cereals, for example.^[48] These values are estimated using country-specific food balance sheets published by the Food and Agriculture Organisation of the United Nations.^[48]

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.

Dietary minerals are

• Calcium (Ca²⁺) is vital to the health of the muscular, circulatory, and digestive systems; is indispensable to the building of bone; and supports the synthesis and function of blood cells. For example, calcium is used to regulate the contraction of muscles, nerve conduction, and the clotting of blood. It can play this role because the Ca²⁺ ion forms stable coordination complexes with many organic compounds, especially proteins; it also forms compounds with a wide range of solubility, enabling the formation of the skeleton.^[57]
• Chlorine as chloride ions; very common electrolyte; see sodium, below.
• Magnesium, required for processing ATP and related reactions (builds bone, causes strong peristalsis, increases flexibility, increases alkalinity). Approximately 50% is in bone, the remaining 50% is almost all inside body cells, with only about 1% located in extracellular fluid. Food sources include oats, buckwheat, tofu, nuts, caviar, green leafy vegetables, legumes, and chocolate.^[58][59]
• Phosphorus, required component of bones; essential for energy processing.^[60] Approximately 80% is found in the inorganic portion of bones and teeth. Phosphorus is a component of every cell, as well as important metabolites, including DNA, RNA, ATP, and phospholipids. Also important in pH regulation. It is an important electrolyte in the form of phosphate.^[61] Food sources include cheese, egg yolk, milk, meat, fish, poultry, whole-grain cereals, and many others.^[58]
• Potassium, a common electrolyte (heart and nerve function). With sodium, potassium is involved in maintaining normal water balance, osmotic equilibrium, and acid-base balance. In addition to calcium, it is important in the regulation of neuromuscular activity. Food sources include bananas, avocados, nuts, vegetables, potatoes, legumes, fish, and mushrooms.^[59]
• Sodium, a common food ingredient and electrolyte, found in most foods and manufactured consumer products, typically as sodium chloride (salt). Excessive sodium consumption can deplete calcium and magnesium.^[62] Sodium has a role in the etiology of hypertension demonstrated from studies showing that a reduction of table salt intake may reduce blood pressure.^[63][64]

Trace minerals

Many elements are required in smaller amounts (microgram quantities), usually because they play a

• coenzymes
• Copper in health
  )
• Chromium required for sugar metabolism
• thyroxin, but probably, for other important organs as breast, stomach, salivary glands, thymus etc. (see Iodine deficiency); for this reason iodine is needed in larger quantities than others in this list, and sometimes classified with the macrominerals;^[66] Nowadays it is most easily found in iodized salt, but there are also natural sources such as Kombu.^[67][68]
• 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, carbonic anhydrase

Ultratrace minerals

Ultratrace minerals are an as yet unproven aspect of human nutrition, and may be required at amounts measured in very low ranges of μg/day. Many ultratrace elements have been suggested as essential, but such claims have usually not been confirmed. Definitive evidence for efficacy comes from the characterization of a biomolecule containing the element with an identifiable and testable function. These include:^[69][70]

• Bromine
• Arsenic
• Nickel
• Fluorine
• Boron
• Lithium
• Strontium
• Silicon
• Vanadium

Vitamins

Except for

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.[72]

Malnutrition

The term malnutrition addresses 3 broad groups of conditions:

• Undernutrition, which includes wasting (low weight-for-height), stunting (low height-for-age) and underweight (low weight-for-age)
• Micronutrient-related malnutrition, which includes micronutrient deficiencies or insufficiencies (a lack of important vitamins and minerals) or micronutrient excess
• Overweight, obesity and diet-related noncommunicable diseases (such as heart disease, stroke, diabetes and some cancers).^[73]

In developed countries, the diseases of malnutrition are most often associated with nutritional imbalances or excessive consumption; there are more people in the world who are malnourished due to excessive consumption. According to the United Nations World Health Organization, the greatest challenge in developing nations today is not starvation, but insufficient nutrition – the lack of nutrients necessary for the growth and maintenance of vital functions. The causes of malnutrition are directly linked to inadequate macronutrient consumption and disease, and are indirectly linked to factors like "household food security, maternal and child care, health services, and the environment."^[3]

Insufficient

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.^[74] The DRI documents describe nutrient deficiency signs and symptoms.

Excessive

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.^[74] The European Food Safety Authority also reviews the same safety questions and set its own ULs.^[75]

Unbalanced

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, sugar and alcohol are referred to as

Phytochemicals such as polyphenols are compounds produced naturally in plants (phyto means "plant" in Greek). In general, the term identifies compounds that are prevalent in plant foods, but are not proven to be essential for human nutrition, as of 2018. There is no conclusive evidence in humans that polyphenols or other non-nutrient compounds from plants confer health benefits, mainly because these compounds have poor bioavailability, i.e., following ingestion, they are digested into smaller metabolites with unknown functions, then are rapidly eliminated from the body.^[82][83]

While initial studies sought to reveal if dietary supplements might promote health, one meta-analysis concluded that supplementation with antioxidant vitamins A and E and beta-carotene did not convey any benefits, and may increase risk of death.^[84] Vitamin C and selenium supplements did not impact mortality rate. Health effect of non-nutrient phytochemicals such as polyphenols were not assessed in this review.^[85]

Intestinal microbiome

The intestines contain a large population of

Global nutrition challenges

This section splitting the content into a new article. (February 2021)

The challenges facing global nutrition are disease, child malnutrition, obesity, and vitamin deficiency.^[medical citation needed]

Disease

The most common non-infectious diseases worldwide, that contribute most to the global mortality rate, are cardiovascular diseases, various cancers, diabetes, and chronic respiratory problems, all of which are linked to poor nutrition. Nutrition and diet are closely associated with the leading causes of death, including cardiovascular disease and cancer. Obesity and high sodium intake can contribute to ischemic heart disease, while consumption of fruits and vegetables

Food-borne and infectious diseases can result in malnutrition, and malnutrition exacerbates infectious disease. Poor nutrition leaves children and adults more susceptible to contracting life-threatening diseases such as diarrheal infections and respiratory infections.[2] According to the WHO, in 2011, 6.9 million children died of infectious diseases like pneumonia, diarrhea, malaria, and neonatal conditions, of which at least one third were associated with undernutrition.^[91][92][93]

Child malnutrition

According to UNICEF, in 2011, 101 million children across the globe were underweight and one in four children, 165 million, were stunted in growth.^[94] Simultaneously, there are 43 million children under five who are overweight or obese.^[3] Nearly 20 million children under five suffer from severe acute malnutrition, a life-threatening condition requiring urgent treatment.^[3] According to estimations at UNICEF, hunger will be responsible for 5.6 million deaths of children under the age of five this year.^[2] These all represent significant public health emergencies.^[90] This is because proper maternal and child nutrition has immense consequences for survival, acute and chronic disease incidence, normal growth, and economic productivity of individuals.^[95]

Childhood malnutrition is common and contributes to the global burden of disease.^[96] Childhood is a particularly important time to achieve good nutrition status, because poor nutrition has the capability to lock a child in a vicious cycle of disease susceptibility and recurring sickness, which threatens cognitive and social development.^[2] Undernutrition and bias in access to food and health services leaves children less likely to attend or perform well in school.^[2]

Undernutrition

UNICEF defines undernutrition "as the outcome of insufficient food intake (hunger) and repeated infectious diseases. Under nutrition includes being underweight for one's age, too short for one's age (stunted), dangerously thin (wasted), and deficient in vitamins and minerals (micronutrient malnutrient).^[2] Under nutrition causes 53% of deaths of children under five across the world.^[2] It has been estimated that undernutrition is the underlying cause for 35% of child deaths.^[97] The Maternal and Child Nutrition Study Group estimate that under nutrition, "including fetal growth restriction, stunting, wasting, deficiencies of vitamin A and zinc along with suboptimum breastfeeding—is a cause of 3.1 million child deaths and infant mortality, or 45% of all child deaths in 2011".^[95]

When humans are undernourished, they no longer maintain normal bodily functions, such as growth, resistance to infection, or have satisfactory performance in school or work.^[2] Major causes of under nutrition in young children include lack of proper breast feeding for infants and illnesses such as diarrhea, pneumonia, malaria, and HIV/AIDS.^[2] According to UNICEF 146 million children across the globe, that one out of four under the age of five, are underweight.^[2] The number of underweight children has decreased since 1990, from 33 percent to 28 percent between 1990 and 2004.^[2] Underweight and stunted children are more susceptible to infection, more likely to fall behind in school, more likely to become overweight and develop non-infectious diseases, and ultimately earn less than their non-stunted coworkers.^[98] Therefore, undernutrition can accumulate deficiencies in health which results in less productive individuals and societies^[2]

Many children are born with the inherent disadvantage of low birth weight, often caused by intrauterine growth restriction and poor maternal nutrition, which results in worse growth, development, and health throughout the course of their lifetime.^[90] Children born at low birthweight (less than 5.5 pounds or 2.5 kg), are less likely to be healthy and are more susceptible to disease and early death.^[2] Those born at low birthweight also are likely to have a depressed immune system, which can increase their chances of heart disease and diabetes later on in life.^[2] Because 96% of low birthweight occurs in the developing world, low birthweight is associated with being born to a mother in poverty with poor nutritional status that has had to perform demanding labor.^[2]

Stunting and other forms of undernutrition reduces a child's chance of survival and hinders their optimal growth and health.^[98] Stunting has demonstrated association with poor brain development, which reduces cognitive ability, academic performance, and eventually earning potential.^[98] Important determinants of stunting include the quality and frequency of infant and child feeding, infectious disease susceptibility, and the mother's nutrition and health status.^[98] Undernourished mothers are more likely to birth stunted children, perpetuating a cycle of undernutrition and poverty.^[98] Stunted children are more likely to develop obesity and chronic diseases upon reaching adulthood.^[98] Therefore, malnutrition resulting in stunting can further worsen the obesity epidemic, especially in low and middle income countries.^[98] This creates even new economic and social challenges for vulnerable impoverished groups.^[98]

Data on global and regional food supply shows that consumption rose from 2011 to 2012 in all regions. Diets became more diverse, with a decrease in consumption of cereals and roots and an increase in fruits, vegetables, and meat products.^[99] However, this increase masks the discrepancies between nations, where Africa, in particular, saw a decrease in food consumption over the same years.^[99] This information is derived from food balance sheets that reflect national food supplies, however, this does not necessarily reflect the distribution of micro and macronutrients.^[99] Often inequality in food access leaves distribution which uneven, resulting in undernourishment for some and obesity for others.^[99]

Undernourishment, or hunger, according to the FAO, is dietary intake below the minimum daily energy requirement.^[48] The amount of undernourishment is calculated utilizing the average amount of food available for consumption, the size of the population, the relative disparities in access to the food, and the minimum calories required for each individual.^[48] According to FAO, 868 million people (12% of the global population) were undernourished in 2012.^[48] This has decreased across the world since 1990, in all regions except for Africa, where undernourishment has steadily increased.^[48] However, the rates of decrease are not sufficient to meet the first Millennium Development Goal of halving hunger between 1990 and 2015.^[48] The global financial, economic, and food price crisis in 2008 drove many people to hunger, especially women and children. The spike in food prices prevented many people from escaping poverty, because the poor spend a larger proportion of their income on food and farmers are net consumers of food.^[100] High food prices cause consumers to have less purchasing power and to substitute more-nutritious foods with low-cost alternatives.^[101]

Adult overweight and obesity

Malnutrition in industrialized nations is primarily due to excess calories and non-nutritious carbohydrates, which has contributed to the obesity epidemic affecting both developed and some developing nations.^[102] In 2008, 35% of adults above the age of 20 years were overweight (BMI ≥ 25 kg/m²), a prevalence that has doubled worldwide between 1980 and 2008.^[103] Also 10% of men and 14% of women were obese, with a BMI greater than 30.^[104] Rates of overweight and obesity vary across the globe, with the highest prevalence in the Americas, followed by European nations, where over 50% of the population is overweight or obese.^[104]

Obesity is more prevalent amongst high income and higher middle income groups than lower divisions of income.^[104] Women are more likely than men to be obese, where the rate of obesity in women doubled from 8% to 14% between 1980 and 2008.^[104] Being overweight as a child has become an increasingly important indicator for later development of obesity and non-infectious diseases such as heart disease.^[95] In several western European nations, the prevalence of overweight and obese children rose by 10% from 1980 to 1990, a rate that has begun to accelerate recently.^[2]

Vitamin and mineral malnutrition

Vitamins and minerals are essential to the proper functioning and maintenance of the human body.^[105] There are 20 trace elements and minerals that are essential in small quantities to body function and overall human health.^[105]

Iron deficiency is the most common inadequate nutrient worldwide, affecting approximately 2 billion people.^[106] Globally, anemia affects 1.6 billion people, and represents a public health emergency in mothers and children under five.^[107] The World Health Organization estimates that there exists 469 million women of reproductive age and approximately 600 million preschool and school-age children worldwide who are anemic.^[108] Anemia, especially iron-deficient anemia, is a critical problem for cognitive developments in children, and its presence leads to maternal deaths and poor brain and motor development in children.^[2] The development of anemia affects mothers and children more because infants and children have higher iron requirements for growth.^[109] Health consequences for iron deficiency in young children include increased perinatal mortality, delayed mental and physical development, negative behavioral consequences, reduced auditory and visual function, and impaired physical performance.^[110] The harm caused by iron deficiency during child development cannot be reversed and result in reduced academic performance, poor physical work capacity, and decreased productivity in adulthood.^[3] Mothers are also very susceptible to iron-deficient anemia because women lose iron during menstruation, and rarely supplement it in their diet.^[3] Maternal iron deficiency anemia increases the chances of maternal mortality, contributing to at least 18% of maternal deaths in low and middle income countries.^[111]

Vitamin A plays an essential role in developing the immune system in children, therefore, it is considered an essential micronutrient that can greatly affect health.^[2] However, because of the expense of testing for deficiencies, many developing nations have not been able to fully detect and address vitamin A deficiency, leaving vitamin A deficiency considered a silent hunger.^[2] According to estimates, subclinical vitamin A deficiency, characterized by low retinol levels, affects 190 million pre-school children and 19 million mothers worldwide.^[112]

The WHO estimates that 5.2 million of these children under five are affected by night blindness, which is considered clinical vitamin A deficiency.^[113] Severe vitamin A deficiency (VAD) for developing children can result in visual impairments, anemia and weakened immunity, and increase their risk of morbidity and mortality from infectious disease.^[114] This also presents a problem for women, with WHO estimating that 9.8 million women are affected by night blindness.^[115] Clinical vitamin A deficiency is particularly common among pregnant women, with prevalence rates as high as 9.8% in South-East Asia.^[112]

Estimates say that 28.5% of the global population is iodine deficient, representing 1.88 billion individuals.^[116] Although salt iodization programs have reduced the prevalence of iodine deficiency, this is still a public health concern in 32 nations. Moderate deficiencies are common in Europe and Africa, and over consumption is common in the Americas.^[90] Iodine-deficient diets can interfere with adequate thyroid hormone production, which is responsible for normal growth in the brain and nervous system. This ultimately leads to poor school performance and impaired intellectual capabilities.^[2]

Infant and young child feeding

Improvement of breast feeding practices, like early initiation and exclusive breast feeding for the first two years of life, could save the lives of 1.5 million children annually.^[117] Nutrition interventions targeted at infants aged 0–5 months first encourages early initiation of breastfeeding.^[3] Though the relationship between early initiation of breast feeding and improved health outcomes has not been formally established, a recent study in Ghana suggests a causal relationship between early initiation and reduced infection-caused neo-natal deaths.^[3] Also, experts promote exclusive breastfeeding, rather than using formula, which has shown to promote optimal growth, development, and health of infants.^[118] Exclusive breastfeeding often indicates nutritional status because infants that consume breast milk are more likely to receive all adequate nourishment and nutrients that will aid their developing body and immune system. This leaves children less likely to contract diarrheal diseases and respiratory infections.^[2]

Besides the quality and frequency of breastfeeding, the nutritional status of mothers affects infant health. When mothers do not receive proper nutrition, it threatens the wellness and potential of their children.^[2] Well-nourished women are less likely to experience risks of birth and are more likely to deliver children who will develop well physically and mentally.^[2] Maternal undernutrition increases the chances of low-birth weight, which can increase the risk of infections and asphyxia in fetuses, increasing the probability of neonatal deaths.^[119] Growth failure during intrauterine conditions, associated with improper mother nutrition, can contribute to lifelong health complications.^[3] Approximately 13 million children are born with intrauterine growth restriction annually.^[120]

Anorexia nervosa

The lifetime prevalence of anorexia nervosa in women is 0.9%, with 19 years as the average age of onset.^{[citation needed]} Although relatively uncommon, eating disorders can negatively affect menstruation, fertility, and maternal and fetal well-being. Among infertile women with amenorrhea or oligomenorrhea due to eating disorders, 58% had menstrual irregularities, according to preliminary research in 1990.^{[121][citation needed]}

Nutrition literacy

The findings of the 2003 National Assessment of Adult Literacy (NAAL), conducted by the US Department of Education, 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^[122] 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.^[123] 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^[123] 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^[124] 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^[123] in order to achieve better health outcomes.

International food insecurity and malnutrition

According to UNICEF, South Asia has the highest levels of underweight children under five, followed by sub-Saharan Africans nations, with Industrialized countries and Latin nations having the lowest rates.^[2]

Industrialized countries

According to

In the United States, 2% of children are underweight, with under 1% stunted and 6% are wasting.^[2]

Canada's Food Guide is an evidence-based education and policy tool provided by Health Canada that is designed to promote healthy eating.^[129]

South Asia

In the United States, the incidence of low birthweight is on the rise among all populations, but particularly among

According to UNICEF, boys and girls have almost identical rates as underweight children under age 5 across the world, except in South Asia.^[2]

Nutrition policy

Nutrition interventions

Nutrition directly influences progress towards meeting the Millennium Goals of eradicating hunger and poverty through health and education.^[2] Therefore, nutrition interventions take a multi-faceted approach to improve the nutrition status of various populations. Policy and programming must target both individual behavioral changes and policy approaches to public health. While most nutrition interventions focus on delivery through the health-sector, non-health sector interventions targeting agriculture, water and sanitation, and education are important as well.^[3] Global nutrition micro-nutrient deficiencies often receive large-scale solution approaches by deploying large governmental and non-governmental organizations. For example, in 1990, iodine deficiency was particularly prevalent, with one in five households, or 1.7 billion people, not consuming adequate iodine, leaving them at risk to develop associated diseases.^[2] Therefore, a global campaign to iodize salt to eliminate iodine deficiency successfully boosted the rate to 69% of households in the world consuming adequate amounts of iodine.^[2]

Emergencies and crises often exacerbate undernutrition, due to the aftermath of crises that include food insecurity, poor health resources, unhealthy environments, and poor healthcare practices.^[2] Therefore, the repercussions of natural disasters and other emergencies can exponentially increase the rates of macro and micronutrient deficiencies in populations.^[2] Disaster relief interventions often take a multi-faceted public health approach. UNICEF's programming targeting nutrition services amongst disaster settings include nutrition assessments, measles immunization, vitamin A supplementation, provision of fortified foods and micronutrient supplements, support for breastfeeding and complementary feeding for infants and young children, and therapeutic and supplementary feeding.^[2] For example, during Nigeria's food crisis of 2005, 300,000 children received therapeutic nutrition feeding programs through the collaboration of UNICEF, the Niger government, the World Food Programme, and 24 NGOs utilizing community and facility based feeding schemes.^[2]

Interventions aimed at pregnant women, infants, and children take a behavioral and program-based approach. Behavioral intervention objectives include promoting proper breast-feeding, the immediate initiation of breastfeeding, and its continuation through 2 years and beyond.^[3] UNICEF recognizes that to promote these behaviors, healthful environments must be established conducive to promoting these behaviors, like healthy hospital environments, skilled health workers, support in the public and workplace, and removing negative influences.^[3] Finally, other interventions include provisions of adequate micro and macro nutrients such as iron, anemia, and vitamin A supplements and vitamin-fortified foods and ready-to-use products.^[3] Programs addressing micro-nutrient deficiencies, such as those aimed at anemia, have attempted to provide iron supplementation to pregnant and lactating women. However, because supplementation often occurs too late, these programs have had little effect.^[2] Interventions such as women's nutrition, early and exclusive breastfeeding, appropriate complementary food and micronutrient supplementation have proven to reduce stunting and other manifestations of undernutrition.^[98] A Cochrane review of community-based maternal health packages showed that this community-based approach improved the initiation of breastfeeding within one hour of birth.^[136] Some programs have had adverse effects. One example is the "Formula for Oil" relief program in Iraq, which resulted in the replacement of breastfeeding for formula, which has negatively affected infant nutrition.^[2]

Implementation and delivery platforms

In April 2010, the World Bank and the IMF released a policy briefing entitled "Scaling up Nutrition (SUN): A Framework for action" that represented a partnered effort to address the Lancet's Series on under nutrition, and the goals it set out for improving under nutrition.

In the US, nutritional standards and recommendations are established jointly by the

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.[140]

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.

Education

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 (FCS) 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.^{[medical citation needed]}

A 1985 US

The protein requirement for each individual differs, as do opinions about whether and to what extent physically active people require more protein. The 2005

The main fuel used by the body during exercise is carbohydrates, which is stored in muscle as glycogen – a form of sugar. During exercise, muscle glycogen reserves can be used up, especially when activities last longer than 90 min.[149]

Maternal nutrition

Paediatric nutrition

Adequate nutrition is essential for the growth of children from infancy right through until adolescence. Some nutrients are specifically required for growth on top of nutrients required for normal body maintenance, in particular calcium and iron.^[150]

Elderly nutrition

Malnutrition in general is higher among the elderly, but has different aspects in developed and undeveloped countries.^[151]

Clinical nutrition

On admission to

Before undergoing surgery, a subject should avoid long periods of fasting. Oral feeding should be established as soon as possible after surgery. Other aspects of nutrition such as control of glucose, reduction in risk factors that causes stress-related catabolism or impairment of gastrointestinal functions, and encourage early physical activity to encourage protein synthesis and muscle functions.^[153]

History of human nutrition

Early human nutrition was largely determined by the availability and palatability of foods.^[154] Humans evolved as omnivorous hunter-gatherers, though the diet of humans has varied significantly depending on location and climate. The diet in the tropics tended^[when?] to depend more heavily on plant foods, while the diet at higher latitudes tended more towards animal products. Analyses of postcranial and cranial remains of humans and animals from the Neolithic, along with detailed bone-modification studies, have shown that cannibalism also occurred among prehistoric humans.^[155]

In 2020, archeological research discovered a frescoed thermopolium (a fast-food counter) in an exceptional state of preservation from 79 in Pompeii, including 2,000-year-old foods available in some of the deep terra cotta jars.^[157]

Nutrition in antiquity

During classical antiquity, diets consisted of simple fresh or preserved whole foods that were either locally grown or transported from neighboring areas during times of crisis.^[158][159]

18th century until today: food processing and nutrition

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Since the

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 the content of many heat-labile nutrients such as certain vitamins and phytochemicals, and possibly other yet-to-be-discovered substances.^[160]

Because of reduced nutritional value, processed foods are often enriched or

Around 3000 BC the

According to Walter Gratzer, the study of nutrition probably began during the 6th century BC. In China, the concept of qi developed, a spirit or "wind" similar to what Western Europeans later called pneuma.^[162] Food was classified into "hot" (for example, meats, blood, ginger, and hot spices) and "cold" (green vegetables) in China, India, Malaya, and Persia.^[163] Humours developed perhaps first in China alongside qi.^[162] Ho the Physician concluded that diseases are caused by deficiencies of elements (Wu Xing: fire, water, earth, wood, and metal), and he classified diseases as well as prescribed diets.^[163] About the same time in Italy, Alcmaeon of Croton (a Greek) wrote of the importance of equilibrium between what goes in and what goes out, and warned that imbalance would result in disease marked by obesity or emaciation.^[164]

Around 475 BC,

Salt, pepper and other spices were prescribed for various ailments in various preparations for example mixed with vinegar. In the 2nd century BC, Cato the Elder believed that cabbage (or the urine of cabbage-eaters) could cure digestive diseases, ulcers, warts, and intoxication. Living about the turn of the millennium, Aulus Celsus, an ancient Roman doctor, believed in "strong" and "weak" foods (bread for example was strong, as were older animals and vegetables).^[167]

The Book of Daniel, dated to the second century BC, contains a description of a comparison in health of captured people following Jewish dietary laws versus the diet of the soldiers of the king of Babylon.^[168][169] (The story may be legendary rather than historical.)

1st to 17th century

Galen was physician to gladiators in Pergamon, and in Rome, physician to Marcus Aurelius and the three emperors who succeeded him.^[170] In use from his life in the 1st century AD until the 17th century, it was

Sometimes forgotten during his life, James Lind, a physician in the British navy, performed the first scientific nutrition experiment in 1747. Lind discovered that lime juice saved sailors that had been at sea for years from scurvy, a deadly and painful bleeding disorder. Between 1500 and 1800, an estimated two million sailors had died of scurvy.^[176] The discovery was ignored for forty years, but after about 1850, British sailors became known as "limeys" due to the carrying and consumption of limes aboard ship.^[177] The essential vitamin C within citrus fruits would not be identified by scientists until 1932.^[176]

Around 1770,

In 1790, George Fordyce recognized calcium as necessary for the survival of fowl. In the early 19th century, the elements carbon, nitrogen, hydrogen, and oxygen were recognized^{[by whom?]} as the primary components of food, and methods to measure their proportions were developed.^[181]

In 1816, François Magendie discovered that dogs fed only carbohydrates (sugar), fat (olive oil), and water died evidently of starvation, but dogs also fed protein survived – identifying protein as an essential dietary component.^[182] William Prout in 1827 was the first person to divide foods into carbohydrates, fat, and protein.^[183] In 1840, Justus von Liebig discovered the chemical makeup of carbohydrates (sugars), fats (fatty acids) and proteins (amino acids). During the 19th century, Jean-Baptiste Dumas and von Liebig quarrelled over their shared belief that animals get their protein directly from plants (animal and plant protein are the same and that humans do not create organic compounds).^[184] With a reputation as the leading organic chemist of his day but with no credentials in animal physiology,^[185] von Liebig grew rich making food extracts like beef bouillon and infant formula that were later found to be of questionable nutritious value.^[186]

In the early 1880s,

In 1896,

In the early 20th century,

In 1919, Sir Edward Mellanby incorrectly identified rickets as a vitamin A deficiency because he could cure it in dogs with cod liver oil.^[193] In 1922, McCollum destroyed the vitamin A in cod liver oil, but found that it still cured rickets.^[193] Also in 1922, H.M. Evans and L.S. Bishop discover vitamin E as essential for rat pregnancy, originally calling it "food factor X" until 1925.

In 1925 Hart discovered that

In the 1930s, William Cumming Rose identified essential amino acids, necessary protein components that the body cannot synthesize. In 1935 Eric Underwood and Hedley Marston independently discovered the necessity of cobalt. In 1936, Eugene Floyd DuBois showed that work and school performance are related to caloric intake. In 1938, Erhard Fernholz discovered the chemical structure of vitamin E.^[194][195] It was synthesised the same year by Paul Karrer.^[194]

Oxford University closed down its nutrition department after World War II because the subject seemed to have been completed between 1912 and 1944.^[196]

Institutionalization of nutritional science in the 1950s

Nutritional science as a separate, independent science discipline was institutionalized in the 1950s. At the instigation of the British physiologist

Further reading

• Hirschfelder, Gunther/Trummer, Manuel, Food and Drink, EGO - European History Online, Mainz: Institute of European History, 2013, retrieved: 8 March 2020 (pdf).
• Mahan, L.K.; Escott-Stump, S., eds. (2000). Krause's Food, Nutrition, and Diet Therapy (10th ed.). Philadelphia: W.B. Saunders Harcourt Brace.
  ISBN 978-0-7216-7904-4
  .
• Human Nutrition. Readings from Scientific American. San Francisco: W.H. Freeman & Co. 1978.
  ISBN 978-0-7167-0183-5
  .
• Thiollet, J.-P. (2001). Vitamines & minéraux. Paris: Anagramme.
• Willett WC, Stampfer MJ (January 2003). "Rebuilding the food pyramid". Scientific American. 288 (1): 64–71.
  PMID 12506426
  .