Macronutrients are substances needed in large quantities, such as carbohydrates and protein, while micronutrients are needed in small amounts and include vitamins and minerals. Vitamins are small chemicals that include the many water-soluble B vitamins and vitamin C. Fat-soluble vitamins include vitamins A, D, E and K. Minerals are naturally-occurring elements that are also needed for health. A dietitian or physician should be consulted regarding dietary and health choices.
Functions
A few vitamins, such as vitamin E, act as antioxidants, which decrease levels of cell-damaging chemicals called free radicals. Most vitamins act as co-factors, which must bind to a protein or enzyme for it to work correctly. For example, an enzyme is required to create collagen, a connective tissue that gives strength and flexibility to skin and other tissues. To work, these enzymes need vitamin C. In this case, vitamin C is a cofactor for collagen synthesizing enzymes. Minerals occasionally act as cofactors, such as iron, which binds to the protein hemoglobin in red blood cells to carry oxygen. Minerals also provide structure, such as calcium in bones. In addition, they help the cells communicate through electrical signals.
Dietary Reference Intakes
The U.S. Department of Agriculture lists the recommended dietary allowances and adequate intakes for vitamins and minerals. The recommended daily intakes vary by age and sex, and for pregnancy and lactation. This is because vitamin and mineral doses will need to increase, to a point, with increasing weight and periods of growth. In addition, pregnancy and lactation require extra vitamins to provide growth to a fetus or infant. A physician or dietitian can help determine individual needs.
Deficiencies
Vitamin deficiencies result in poor health because the functions enabled by the vitamins will no longer work. Enzymes that require vitamins will function inefficiently if at all. The symptoms will depend on the deficiency. For example, in vitamin C deficiency, collagen is not synthesized, and the connective tissue becomes weak. Mucous membranes such as the gums bleed easily, and bruising is common from weak blood vessel walls. Mineral deficiencies are similar in concept. For example, a calcium deficiency can weaken bones and disturb nerves and muscles that use calcium to communicate.
Toxicity
Vitamins and minerals can be too much of a good thing. It is important to not exceed the recommended daily allowances unless directed otherwise by a health care professional. The water-soluble B vitamins tend to be less toxic because the kidneys can excrete excess buildup more easily. The fat soluble vitamins tend to deposit in the tissues and can build up to toxic levels. Mineral excesses can be dangerous over the short or long term.
References
- "Robbins and Cotran Pathologic Basis of Disease (eighth edition)"; Vinay Kumar et al; 2009
- "Nutrition Concepts and Controversies (11th edition"; Frances Sizer, Ellie Whitney; 2007
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