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Elements of the Body

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Lithium, boron, fluorine, silicon, vanadium, nickel, bromine, and strontium have no established biochemical functions; however, their deprivation shows impaired function. The importance of all other elements found in the body have little circumstantial and no direct evidence of biological function and are thought of more as contaminants than nutrients (aluminum, germanium, arsenic, rubidium, tin, and lead). Since large quantities, >100 mg/day, of phosphorus, sulfur, calcium, sodium, potassium, magnesium and chloride are required, they are considered macronutrients. These elements must be consumed, digested, and absorbed through diet before they can be assembled as molecular building blocks to perform a required biological function. Nutrients provide the essential elements and molecules vital for human life, which can be divided into water, the three primary macronutrients, protein, carbohydrates, and lipids, and two micronutrients, vitamins and minerals. In addition to the six nutrients, phytochemicals describe compounds that may not be essential for life but could improve health.

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Water

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Macronutrients: Carbohydrates, Lipids, Proteins

Macronutrients are required in gram amounts to provide energy and molecules needed for maintenance, including carbohydrates, lipids, and proteins; calcium, phosphorus, potassium, sodium, chlorine, sulfur, and magnesium are all required in gram quantities. Carbohydrates, lipids and proteins provide 4 Kcal/g, 9 Kcal/g, and 4 Kcal/g, respectively. Carbohydrates comprising carbon, hydrogen and oxygen are defined as a compound containing those three elements with twice the hydrogen atoms compared to carbon and oxygen atoms (CH₂O). Acceptable carbohydrate consumption accounts for 45–65% of the daily calorie intake based on the average daily minimum amount of glucose utilized by the brain, equating to ~130 g/day. Three categories subdivide carbohydrates into simple sugars (1 or 2 monosaccharides), oligosaccharides (3-9 monosaccharides), and polysaccharides (> 10 monosaccharides). The latter two carbohydrates are further subdivided into digestible (glycemic: contains α-1-4 bonds) and non-digestible (non-glycemic, fiber: contains α-1-6 bonds); glycemic carbohydrates provide carbon, oxygen and hydrogen, and the hydrolyzed glucose is used as energy by various tissues in the body, including the brain. Simple carbohydrates include one (e.g., glucose, fructose, galactose) or two (e.g., sucrose, lactose, maltose) monosaccharides. The body synthesizes glucose from proteins via gluconeogenesis when insufficient carbohydrates are consumed. Although non-glycemic carbohydrates are not digested into monosaccharides, they are essential for helping rid the body of waste while maintaining a healthy intestinal tract.

Proteins are polymers of proteinogenic amino acids, meaning they are biosynthetically incorporated into proteins during translation and ideally account for 10-30% of the daily caloric intake. Amino acids are of utmost importance in providing the building blocks to construct proteins such as collagen, enzymes, and organelles, as well as enzymes to break down foods, grow, repair tissue, and in other bodily functions. Amino acids share homology, where a central carbon is attached to an amino and acid group, and variations of amino acids arise from the side group attached to the central carbon. Amino acids are subdivided into essential, which the body cannot synthesize; nonessential, which the body synthesizes; and conditional, which are not usually essential but can be during times of stress or illness. Nonessential amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine of those arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine are conditional amino acids; nine essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Naturally occurring L-amino acids are also categorized based on their side chain functionality; positively-charged amino acids at physiological pH (~7.4) include arginine (arg, R), histidine (his, H), and lysine (lys, K); negatively-charged amino acids include aspartic acid (asp, D) and glutamic acid (glu, E). The polar uncharged amino acids are serine (ser, S), threonine (thr, T), asparagine (asn, N), and glutamine (gln, Q); hydrophobic side chains include alanine (ala, A), valine (val, V), isoleucine (ile, I), leucine (leu, L), and methionine (met, M), phenylalanine (Phe, F), tyrosine (tyr,Y), and tryptophan (trp, W). Glycine (gly, G), proline (pro, P) and cysteine (cys, C) comprise the last category of special amino acids.

Proteins are polymers of proteinogenic amino acids, meaning they are biosynthetically incorporated into proteins during translation and ideally account for 10-30% of the daily caloric intake. Amino acids are of utmost importance in providing the building blocks to construct proteins such as collagen, enzymes, and organelles, as well as enzymes to break down foods, grow, repair tissue, and in other bodily functions. Amino acids share homology, where a central carbon is attached to an amino and acid group, and variations of amino acids arise from the side group attached to the central carbon. Amino acids are subdivided into essential, which the body cannot synthesize; nonessential, which the body synthesizes; and conditional, which are not usually essential but can be during times of stress or illness. Nonessential amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine of those arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine are conditional amino acids; nine essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Naturally occurring L-amino acids are also categorized based on their side chain functionality; positively-charged amino acids at physiological pH (~7.4) include arginine (arg, R), histidine (his, H), and lysine (lys, K); negatively-charged amino acids include aspartic acid (asp, D) and glutamic acid (glu, E). The polar uncharged amino acids are serine (ser, S), threonine (thr, T), asparagine (asn, N), and glutamine (gln, Q); hydrophobic side chains include alanine (ala, A), valine (val, V), isoleucine (ile, I), leucine (leu, L), and methionine (met, M), phenylalanine (Phe, F), tyrosine (tyr,Y), and tryptophan (trp, W). Glycine (gly, G), proline (pro, P) and cysteine (cys, C) comprise the last category of special amino acids.

The remaining 20-35% of calories are attained from lipids, used for energy storage, hormone production, and cell membrane integrity while aiding in the absorption of fat-soluble micronutrients. Lipids are most commonly consumed as triglycerides, with three fatty acids esterified onto glycerol. Fatty acids contain a carboxylic acid attached to a hydrocarbon chain ranging between 2 and 26 carbons classified as saturated, monounsaturated, polyunsaturated, and trans fats. Dietary short-chain saturated fatty acids include butyric acid (C4), caproic (C6), caprylic (C8), and capric (C10) acids, while acetic (C2) and propanoic (C3) along with butyric acid are gut bacterial metabolites. Medium-chain fatty acids include lauric (C12), myristic (C14) and palmitic acids (C16); while long-chain saturated fatty acids are stearic (C18), arachidic (C20), behenic (C22), lignoceric (C24) and cerotic acid (C26). Monounsaturated fatty acids contain one cis configuration double bond varying in position on the hydrocarbon chain and vary in length from myristoleic (C14:1), palmitoleic (C16:1Δ⁹) or sapienic (C16:1, Δ⁶), oleic (C18:1) and erucic acid (C22:1). The position of unsaturated is either denoted using IUPAC system (denoted Δ) starting from the carboxylic acid end or the omega system (denoted ω) starting at the carbon end. Polyunsaturated fatty acids contain more than one cis configuration double bond and vary in hydrocarbon chain length and double bond position. Polyunsaturated fatty acids include linoleic (C18:2), α-linolenic (C18:3), arachidonic (C20:4), eicosapentaenoic (C20:5) and docosahexaenoic acid (C22:6). The two fatty acids, α-linolenic acid (18:3), an ω-3 fatty acid, and linoleic acid (18:2), an ω-6 fatty acid, are considered essential as humans can modify them into other omega-6 and omega-3 fatty acids through a series of desaturation (addition of a double bond between two carbon atoms) and elongation (addition of two carbon atoms) reactions. The final classification differs based on the geometric isomerization of the double bond; trans fatty acids can be either monounsaturated, including elaidic acid (C18:1 Δ⁹), vaccenic (C18:1 Δ¹¹), or polyunsaturated, including linoelaidic acid (trans-C18:2). Fatty acids with both trans and cis configuration are included as trans fatty acids; conjugated linoleic acid (CLA) has 18 carbons, a trans configuration at C10, and a cis at C12, or with the trans bond at C11 and cis at C9. Trans fatty acids are rare but occur naturally in the digestive tract of ruminants; most trans fats in the diet were of industrial origin via the partial hydrogenation of fats.

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Essential Macrominerals

Iron RDA (mg/day): Child (10); Adult Male (8); Adult Female (15-18); Pregnant (27); Lactating (10): >70 Male (na): >50 Female (na). Dietary sources:  Meat, poultry, seafood and organ meat supply iron as heme; whole grains, nuts, seeds, legumes, leafy greens, and fortified foods as non-heme. Role: Iron is a major component of hemoglobin in red blood cells responsible for carrying oxygen. Iron is stored as ferritin in the liver, spleen, muscle, bone marrow and various tissues and delivered via the circulatory system bound to transferrin.

Zinc RDA (mg/day): Child (5); Adult Male (11); Adult Female (8); Pregnant (12); Lactating (13): >70 Male (na): >50 Female (na). Sources: Shellfish, meat, legumes, nuts, whole grains, and fortified in breakfast cereal. Role: Zinc is required by the immune system, is a cofactor for more than 100 enzymes, and is required for synthesizing DNA, cell growth, and repairing damaged tissue. Zinc is homeostatically regulated by altering the absorption and excretion in feces and urine.

Copper RDA (µg/day): Child (440); Adult Male (900); Adult Female (900); Pregnant (1000); Lactating (1000): >70 Male (900): >50 Female (900). Dietary sources: Shellfish, salmon, liver, cashews, potatoes and spinach. Role: Copper is a component of enzymes, aids iron absorption, and is used for red blood cells, collagen, connective tissue, and neurotransmitters; it is required for brain development, immune functions and superoxide dismutase. Copper is absorbed in the small intestine and stored in bones and muscle tissue. Copper homeostasis occurs in the liver, which removes excess from the body following absorption in the duodenum.

Iodine RDA (µg/day): Child (10); Adult Male (150); Adult Female (150); Pregnant (220); Lactating (290): >70 Male (150): >50 Female (150). Dietary sources: Iodized table salt, shellfish, dairy, eggs, liver, and seaweed. Role: Iodine is needed for thyroid hormones to assist proteins and enzyme synthesis and to regulate metabolism, growth, development and reproduction. Homeostatic control of iodine occurs primarily in the thyroid, where it is trapped using a precursor protein of thyroid hormone from circulating blood.

Molybdenum RDA (µg/day): Child (22); Adult Male (45); Adult Female (45); Pregnant (350-360); Lactating (290): >70 Male (na): >50 Female (na). Dietary sources: Wine, beer, legumes, dairy, fortified whole grain cereals, and bananas. Role: Molybdenum is contained in enzymes responsible for hydrolyzing proteins, alcohol, drugs, toxins, purines and sulfites. Homeostatic control of molybdenum maintains stores in the liver, kidneys, and bone while the kidneys excrete the excess in urine.

Selenium RDA (µg/day): Child (30); Adult Male (55); Adult Female (55); Pregnant (60); Lactating (70): >70 Male (na): >50 Female (na). Dietary sources: Shellfish, meat, fortified breakfast cereals, beans and lentils. Role: Selenium is contained in selenoproteins (enzymes) involved in DNA synthesis, protecting against cell damage and infections, reproduction, and the metabolism of thyroid hormones. Selenium is part of the homeostatic response to oxidative stress and is stored in muscle and thyroid glands.

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Essential Vitamins

Vitamin A RDA (µg/day): Child (400); Adult Male (900); Adult Female (700); Pregnant (770); Lactating (1300); >70 Male (900); >50 Female (700). Vit A is a set of fat-soluble vitamers, including all-trans-retinol (retinal, retinoic acid, retinol) supplied from animal sources (fish, dairy products, liver) and provitamin A carotenoids (α-, β-, γ-carotene, xanthophyll)) derived from plants (yellow and orange vegetables and dark leafy greens). Deficiencies are typified by night blindness and skin thickening (stratum corneum), while toxic levels cause Hypervitaminosis A.

Thiamin (Vit B₁) RDA (mg/day): Child (0.6); Adult Male (1.2); Adult Female (1.1); Pregnant (1.4); Lactating (1.4); >70 Male (na); >50 Female (na). Vitamin B contains eight (B₁, B₂, B₃, B₅, B₆, B₇, B₉, and B₁₂) water-soluble vitamins, making toxicity very rare as excess is excreted by the kidneys, with many comprised of multiple vitamers. Vit B₁ contains vitamers thiamine, thiamine monophosphate, and thiamine pyrophosphate (TPP); the vitamer TPP is a cofactor in the citric acid cycle, the central metabolic pathway involved in carbohydrate, lipid, and amino acid metabolism, and when deficient, leads to muscle wasting. Thiamine deficiency inhibits the production of neurotransmitters glutamic acid and γ-Aminobutyric acid (GABA), resulting in loss of muscle function, numbness in hands and feet, confusion, and nystagmus (involuntary eye movements); that, together with muscle wasting, are the primary characteristics of beriberi. One population especially prevalent with thiamine deficiencies includes alcoholics, as the active transport of thiamine from the GI is disrupted during acute alcohol exposure. Sources of thiamine include whole grains, brown rice, vegetables, eggs, and liver.

Riboflavin (Vit B₂) RDA (mg/day): Child (0.6); Adult Male (1.3); Adult Female (1.1); Pregnant (1.4); Lactating (1.6); >70 Male (1.2); >50 Female (1.1). Vit B_2, riboflavin, is a single vitamin absorbed at the proximal small intestine, required as cofactors for the enzymes flavin mononucleotide and flavin adenine dinucleotide, which are used in antibody production, glucose metabolism, cellular respiration and growth. Unused riboflavin is not stored in the body; the excess is excreted in the urine. Good sources of riboflavin include dairy, eggs, meat, fish, almonds, spinach, and fortified breakfast cereal. Riboflavin deficiency presents as ariboflavinosis, leading to skin disorders, hair loss, reproductive problems, and liver and nervous system degeneration.

Niacin (Vit B₃) RDA (mg/day): Child (8); Adult Male (16); Adult Female (14); Pregnant (18); Lactating (17); >70 Male (16); >50 Female (14). Vit B₃, or niacin, comprises vitamers nicotinic acid and nicotinamide absorbed in the small intestine, the latter of which can be synthesized in the body from tryptophan, and excess consumption is excreted in the urine. Niacin is a coenzyme with > 400 enzymes needed to convert nutrients into energy, synthesize cholesterol and fats, to create and repair DNA. Common food sources include meat, fish, brown rice, nuts, and legumes, fortified in breakfast cereals and bread. Pellagra arises with severe niacin deficiency characterized by dementia, dermatitis, diarrhea and eventually death.

Pantothenic acid (Vit B5) AI (mg/day): Child (0.6); Adult Male (5); Adult Female (5); Pregnant (6); Lactating (7); >70 Male (5); >50 Female (5). Vit B₅, pantothenic acid, is used to make coenzyme A, which aids other enzymes in breaking down and building fatty acids and is needed to synthesize cholesterol, while its deficiency prevents the breakdown and clearance of fats in the blood, leading to high cholesterol/triglycerides, rheumatoid arthritis, impaired skin and wound healing. Also, it aids in building red blood cells and producing sex and stress-related hormones in the adrenal glands. Toxicity is rare as it is water soluble and excreted by the kidneys in urine. Vit B₅ is found in most foods (yeast, vegetables, leafy greens, legumes, lentils, eggs, meat, and fish) but is readily broken down during processing.

Vitamin B₆ RDA (mg/day): Child (0.6); Adult Male (1.7); Adult Female (1.5); Pregnant (1.9); Lactating (2.0); >70 Male (na); >50 Female (na). Vit B₆ (vitamers: pyridoxine, pyridoxal, pyridoxal-5-phosphate, pyridoxamine, pyridoxamine-5-phosphate, pyridoxine-5-phosphate) is essential for 150 biochemical reactions, some of which are involved in the breakdown and clearance of fats (Stach et al., 2021). VitB₆ is found in organ meat, meat, chickpeas, mushrooms, nuts, dairy, and brown rice and is added to fortified cereals. Vit B₆ deficiency causes microcytic anemia due to insufficient hemoglobin translating to small red blood cells, increased pro-inflammatory cytokines, dermatitis, confusion, weakened immune function, and neuritis. Dietary phosphorylated vitamers of B₆ are hydrolyzed before absorption by the intestinal cell, where they are phosphorylated, accumulated and stored in the absorptive cell. Homeostatic regulation of VitB₆is not fully established, but as they become depleted, the stored vitamers are dephosphorylated and transferred to circulation across the basolateral membrane.

Biotin (Vit B₇) AI (µg/day): Child (12); Adult Male (30); Adult Female (30); Pregnant (30); Lactating (35); >70 Male (na); >50 Female (700). Vitamin B₇, biotin, assists carboxylase enzymes responsible for macronutrient digestion required for ATP production, gene expression, and regulation of cellular metabolism, proliferation, oxidative stress, and survival. Vit B₇ is found in eggs, fish, pork, avocados, nuts and seeds and is produced by the gut microbiome. Vit B₇ deficiency leads to neurological disorders, dermal abnormalities, and inflammation (Agrawal et al., 2016). Homeostatic regulation of Vit B7 is closely controlled, and biotin is recycled from peptide fragments from the biotinylation of apocarboxylase.

Folate (Vit B₉) RDA (µg/day): Child (200); Adult Male (400); Adult Female (400); Pregnant (600); Lactating (500); >70 Male (na); >50 Female (na). Vitamin B₉ (vitamers folic acid and folates (tetrahydrofolate, 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, and 10-formylfolic acid)) is used to produce DNA and RNA, in protein metabolism including the break down of homocysteine, in producing red blood cells and critical in periods of rapid growth (e.g., pregnancy and fetal development). Deficiencies of Vit B₉ include neural tube defects, heart disease, cognitive function, and dementia. It is found as folates in dark green leafy vegetables, peanuts, beans, and eggs and fortified in breakfast cereals using folic acid. Homeostatic regulation of vit B₉ actively transports folates after they are converted to monoglutamates in the gut into hepatic circulation before being taken up by various tissues. These stores are available during dietary deprivation, and folates are recycled by the liver and disturbed to actively proliferating cells (Steinberg, 1984).

Cobalamins (Vit B₁₂) RDA (µg/day): Child (1.2); Adult Male (2.4); Adult Female (2.4); Pregnant (2.6); Lactating (2.8); >70 Male (na); >50 Female (na). Vitamin B₁₂ (vitamers of cobalamins: hydroxocobalamin, aquocobalamin, methylcobalamin, and 5′-deoxyadenosylcobalamin), and its precursor, cyanocobalamin, is the only vitamin to contain a metal ion (cobalt). Cyanocobalamin and hydroxocobalamin do not have biological activity but can be converted in the liver to biologically active methylcobalamin and 5′-deoxyadenosylcobalamin. Vit B₁₂ is only produced by microorganisms and incorporated as the dietary source in organ meat, fish, meat, eggs, and dairy. Vit B₁₂ binds to intrinsic factor and is absorbed in the terminal ileum. Vit B₁₂ deficiencies are rare as the intrinsic factor limits uptake, and when the intrinsic factor is low, it leads to pernicious anemia. Vit B₁₂ deficiency can cause macrocytic hyperchromic anemia and funicular myelitis neurological disorder (Back & Biesalski, 2008).

Vitamin C RDA (mg/day): Child (25); Adult Male (90); Adult Female (75); Pregnant (85); Lactating (120); >70 Male (na); >50 Female (na). Vitamin C (ascorbic acid) was the first known nutritional requirement term ‘ascorbic nature’ as the molecule had yet been identified. In 1795 Gilbert Blane, a physician, convinced the British Royal Navy to issue a form of citrus juice to its sailors to prevent scurvy, which at first causes bleeding and bruising from breaking blood vessels, swelling or bleeding of gums followed by tooth and hair loss, and delayed healing of skin wounds, if left untreated leads to death. Vit C is water soluble and found in cruciferous vegetables, peppers and tomatoes; any excess intake is excreted in the urine. Vit C mega dosing and dietary supplements were popularized by Linus Pauling, the only person to win two unshared Nobel prizes; his first in chemistry in 1956 for orbital theory and the chemical bond and peace prize in 1962 for promoting nuclear disarmament.

Vitamin D RDA (µg/day): Child (15); Adult Male (15); Adult Female (15); Pregnant (15); Lactating (15); >70 Male (20); >50 Female (20). Vitamin D (Vitamers of ergocalciferol (D₂ mainly found at low concentration in plants) and cholecalciferol (D₃ produced by humans and consumed as animal products)) are the only vitamers that our body can produce as hormones when exposed to ultraviolet-B rays, and is essential in absorbing, retaining, and incorporating calcium and phosphorus into bones. Fatty fish, egg yolk, and liver are the primary dietary sources, but Vit D is fortified in breakfast cereal and orange juice; Vit D₂ is found in relatively high concentrations in mushrooms.

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Other Essential Nutrients

Choline AI (µg/day): Child (250); Adult Male (550); Adult Female (425); Pregnant (450); Lactating (550); >70 Male (550); >50 Female (425). Choline was deemed nonessential until 1998 (Carver, 2006)as it is produced in the liver as phosphatidylcholine, but natural synthesis is insufficient to meet its requirements for fat transport and metabolism and cell structure and messaging; therefore, dietary sources are required to meet biological needs (Chester et al., 2011). Choline is a small water-soluble organic compound, a quaternary ammonium compound, converted to acetylcholine, essential in muscle contractions, brain function, and pain response. Animal products (meat, fish, poultry, dairy, and eggs) have the highest choline concentration, while it is also found in legumes, mushrooms, and cruciferous vegetables. Choline is metabolized in the liver to phosphatidylcholine, which builds proteins to circulate lipids and break down cholesterol. Toxic intakes of choline cause low blood pressure and is toxic to the liver. Choline is cardioprotective because it lowers homocysteine; if deficient nonalcoholic fatty liver occurs due to excess fat storage and impaired cognitive function, such as Alzheimer’s disease.

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Conditionally Essential Nutrients

Biological pathways exist for conditionally essential nutrients; however, the organic molecules synthesized under certain conditions become insufficient to meet metabolic demand. Biosynthetic capacity often fails to meet the metabolic demand in some disease states, during rapid growth, and for preterm neonates delivered before 37 weeks of pregnancy. Choline was originally classified as a conditionally essential nutrient in addition to carnitine, inositol, taurine, arginine, glutamine, and nucleotides. Carnitine de novo synthesis is possible in the liver, but it is deficient when liver disease occurs and in infants because the synthetic capacity is not fully developed. Carnitine is a component of breastmilk; therefore needs to be supplemented in infant formulas (Indyk, 2006). Inositol is a conditionally essential pseudovitamin for people with diabetes to improve nerve conduction and lung function in preterm infants with respiratory distress syndrome. Taurine, an amino sulfonic acid found in meat, eggs, and fish, displays bioactivity supporting nerve growth in the brain and calms the central nervous system lowering blood pressure and possibly benefiting those with heart failure. While there is a lack of sufficient evidence, taurine is also commonly found in energy drinks as it is proposed to delay fatigue. The amino acids arginine and glutamine, normally considered nonessential as de novo biochemical synthesis pathways exist, can fail to meet biological demand to build protein; as such, they are enriched in protein supplements for athletes. Arginine is a vasodilator (dilates blood vessels) used to treat heart conditions, erectile dysfunction, and preeclampsia (high blood pressure during pregnancy). Glutamine is the most abundant amino acid used to construct proteins in the body. Nucleotides have three components: a nitrogen-containing base found in DNA as adenine, guanine, thymine, or cytosine and in RNA as adenine, guanine, uracil, or cytosine; a phosphate group; and a deoxyribose sugar in DNA and ribose in RNA. Nucleotides perform biochemical functions in synthesizing DNA and RNA, which are potentially essential for formula-fed newborns as they are at a sufficient concentration in human milk; thus, infant formulas are increasingly supplemented with the 5’monophosphate nucleotides (Indky, 2006).

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Nonessential Nutrients

Nonessential nutrients, including insoluble and soluble fiber, significantly impact health. Although all of the fiber passes the small intestine intact, it exerts important biological effects in the colon, including binding and excreting bile, thereby reducing cholesterol, preventing constipation and acting as an energy source for the gut microbiome. In turn, the metabolites of the microbiome, short-chain fatty acids (acetate, propionate, butyrate and isobutyrate), are used as an energy source for the cells lining the large intestine. In addition to nonessential nutrients, non-nutrients provide empty calories but no other purpose and include ethanol which provides 7 kcal.

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Phytochemicals

Phytochemicals broadly include all nutritional and non-nutritional molecules consumed from edible plants. In addition to the compounds discussed above, numerous other biologically active molecules are suggested to improve health but are not deemed essential. Phytochemicals include innumerable nonvitamin micronutrients, likely far more than known, that are nutritionally active and found at low concentrations exerting beneficial and protective properties such as antioxidants, growth promoters, antimicrobials, and immune modulators (Indyk 2006).

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Works Cited

Agrawal, S., et al., 2016. Biotin deficiency enhances the inflammatory response of human dendritic cells. American Journal of Physiology Cell Physiology. 311: C386–C391.
Back, E. & Biesalski, H.K. 2008. Vitamin B12. Encyclopedia of Molecular Pharmacology. Springer, Berlin, Heidelberg 1291-1293.
Berdanier, Carolyn D.; Dwyer, Johanna T.; Heber, David (2013). Handbook of Nutrition and Food (3rd ed.). CRC Press. p. 199. ISBN 978-1-4665-0572-8. Retrieved 3 July 2016.
Carver, J. 2006. Conditionally essential nutrients: Choline, inositol, taurine, arginine, glutamine and nucleotides. In P. Thureen & W. Hay, Neonatal Nutrition and Metabolism. Cambridge: Cambridge University Press. 299-311.
Chester, D.N., et al., 2011. Dietary Intakes of Choline: What We Eat in America, NHANES 2007-2008. Food Surveys Research Group Dietary Data Brief No. 9. http://ars.usda.gov/Services/docs.htm?docid=19476
Stach, K., et al. 2021. Vitamin B6 in Health and Disease. Nutrients. 13: 3329.
Steinberg, S.E. 1984. Mechanisms of folate homeostasis. Journal of Physiology. 246:G319-324.
Health Canada. 2010. Dietary Reference Intakes. www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/dietary-reference-intakes/tables/reference-values-elements-dietary-reference-intakes-tables-2005.html Accessed 2023/02/14
Indyk H; Committee on Food Nutrition. 2006. Nonvitamin micronutrients. Journal of AOAC International. 89: 288-289.