11.11: Vitamins

Characteristics

Vitamins are a diverse group of substances that have five features in common.

1. They are needed in relatively small quantities.
2. They are essential because certain chemical reactions cannot occur effectively without them.
3. They must be obtained in the diet because the body cannot make them in adequate amounts.
4. They must be eaten regularly because they are stored in limited quantities and are gradually lost.
5. A deficiency in each vitamin results in at least one specific disorder.

(Suggestion 249.02.03)

One main group consists of the fat-soluble vitamins (vitamins A, D, E, and K), so called because they dissolve in fat. See the videos "Vitamins and Minerals" (https://blausen.com/en/video/vitamins-and-minerals/) and "Overview of Vitamins and Minerals" (https://blausen.com/en/video/overview-of-vitamins-and-minerals/).

Fat-soluble vitamins are efficiently absorbed only if there is some fat in the diet. They can be stored in fairly large quantities in the liver and other areas of the body that contain high concentrations of fat.

All other vitamins are water-soluble vitamins. The body is less able to store these vitamins because they move freely among the water-containing spaces and are easily lost in the urine.

Sources

Vitamins are found in different amounts in various foods. Since no single food contains adequate amounts of all the vitamins, maintaining vitamin homeostasis requires one regularly to eat a variety of foods. A diet based on MyPlate may provide a healthy adult of any age with adequate amounts of all vitamins (https://www.choosemyplate.gov/ or put https://www.choosemyplate.gov/ into the place of the URL in your browser). More age-adjusted information is at MyPlate for elders (http://www.nutrition.tufts.edu/research/myplate-older-adults and https://www.nal.usda.gov/fnic/older-individuals) and “Healthy Eating Plate” (https://www.health.harvard.edu/plate/healthy-eating-plate).

Using vitamin supplements to augment dietary intake is generally not recommended because this can reduce the dietary intake of other nutrients and because high levels of certain vitamins can injure body cells and cause other disorders (e.g., diarrhea). However, vitamin supplements may be necessary for individuals who do not eat enough varieties or quantities of food and people with abnormal conditions. Such conditions include ones that prevent adequate absorption or use of vitamins and ones that cause excess destruction or elimination. Vitamin supplements may also be used to treat certain diseases (e.g., vitamin D for osteoporosis). Supplements with vitamins A, C, and E, and β-carotene, which serve as antioxidants, seem to reduce the risk of certain diseases related to damage from free radicals (e.g., atherosclerosis, Alzheimer's disease, cancer).

Deficiencies and Excesses

Many cases of vitamin deficiency among the elderly result from eating too little food or a limited variety of food because of alcoholism or other unfavorable factors. Furthermore, some deficiencies develop because vitamins are destroyed or lost when foods are washed, cooked, or processed in other ways. Studies of vitamin status among the elderly show that deficiencies in vitamins A, D, B6, B12, and C; thiamine; riboflavin; and folate occur frequently. Examples of adverse changes from deficiencies in these vitamins include: infections and disorders of the skin and eyes (vitamin A); weak bones (vitamin D); anemia and poor functioning of the nervous and immune systems, excess blood homocysteine (vitamin B6); anemia and nervous system malfunction, excess blood homocysteine (vitamin B12); edema and poor healing (vitamin C); muscle weakness and nervous system malfunctions (thiamine); inflammation of the mouth and skin, and poor vision (riboflavin); anemia and poor functioning of the nervous and digestive systems (folate). Vitamin excesses are rare and almost always result from ingesting vitamin supplements.

Vague or nonspecific symptoms such as nausea, loss of appetite, and mental, emotional, or personality changes may occur with many cases of mild vitamin deficiency or excess. Other adverse changes that are specific for each vitamin deficiency may be barely detectable at first.

See Facts About Vitamins.

For detailed information about vitamins, go to https://www.biologyofhumanaging.com/tblvit - true.htm .