Vitamin C chelates non-heme iron in food while exposed to the acidic pH of the stomach. This chelated iron then becomes more soluble in the alkaline pH of the duodenum, resulting in increased intestinal absorption of iron.

Serotonin, melatonin, and niacin are all synthesized from L-tryptophan, an amino acid prevalent in many foods including chocolate, oats, dates, milk, sesame seeds, eggs, meat, and cheese. L-tyrosine is involved in the synthesis of dopamine. Acetylcholine is the neurotransmitter released at the neuromuscular junction, which stimulates contraction of skeletal muscle. Taurine has many biological functions in the cardiovascular, muscular, and nervous systems, as well as others.

Biotin, or vitamin B7, plays an important role in the health of the hair, nails, and skin. Deficiency generally manifests as alopecia, loss of hair color, brittle nails, and dermatitis.

Offering a treatment plan that includes specific nutrient supplementation and a dietary protocol is a normal part of a nutritional counseling and intervention. Initiating tube feeding is only necessary in cases of anorexia or other forms of malnourishment, but is still within normal procedures. Admonishing patients for their dietary choices, however, would be counterproductive to the nurse's attempt to foster trust and willingness on the part of the patient, and so would be inappropriate in an intervention setting.

Kwashiorkor is a condition of sufficient caloric intake with severe protein malnutrition, often seen in impoverished areas where individuals must survive on carbohydrate-based sources of nutrition. This results in a severe deficiency of albumin, with symptoms such as edema, ascites, fatty liver, and dermal ulceration. Marasmus is a condition not specifically of protein deficiency but of general starvation, which may be due to lack of food security or to intentional fasting or extreme caloric restriction. Pellagra is a condition caused by niacin deficiency, and beriberi is a thiamine deficiency syndrome with neurological, gastrointestinal, and cardiac manifestations.

Hypervitaminosis D, or vitamin D toxicity, has been known to cause calcification in soft tissues due to vitamin D's role in calcium absorption and metabolism. None of the other nutrients are as closely related to calcium metabolism, and do not cause hypercalcification in soft tissues when overconsumed.

Methylene tetrahydrofolate reductase (MTHFR) is an enzyme with multiple important metabolic roles, including the methylation of folate, vitamin B12, and homocysteine. MTHFR deletions can result in folate and B12 related anemias and high homocysteine due to interruption of homocysteine recycling into methionine.

Essential amino acids are amino acids that can not be synthesized within the body, but must be consumed through the diet. Tryptophan is the only essential amino acid listed. In all, there are 9 essential amino acids. 

All of the criteria listed and AI (Adequate Intake) (not listed) must be taken into account when establishing a Daily Reference Intake (DRI) except for ADI (Active Daily Intake), which is a fictitious criteria.

The most abundant mineral in the human body is calcium. It is primarily stored in the bones and the teeth, and makes up half of the total weight of the skeleton. In addition, calcium is present in nerves, muscle cells, blood, kidneys, and various other soft tissues of the body.