22.7: Vitamins and minerals are necessary for good health.

It would be nice if we could take a pill that would make us more healthy or fit. Vitamins are not such a miracle pill. They’re a bit like security guards at a museum: above a certain number, they don’t make the museum any better, but in their absence, the museum is likely to become a whole lot worse. And while vitamin supplements are not a health panacea, vitamins and minerals do have an important role in nutrition.

Vitamins are organic compounds that are essential nutrients required by the body in small amounts for normal growth and health. Minerals are the chemical elements, other than those commonly found in organic molecules—carbon, hydrogen, oxygen, and nitrogen—some of which are required in the diet in small amounts. There are three features common to all vitamins and minerals.

• 1. They don’t yield any usable energy. Rather, they serve as collaborators with enzymes to enable the processing of the proteins, carbohydrates, and fats we eat, and they catalyze a wide range of other chemical reactions around the body.
• 2. They need to be consumed in much smaller amounts than proteins, carbohydrates, and fats in our diet. This is because they tend to serve as reaction catalysts and so can be recycled and reused again and again.
• 3. If we have a healthy diet, we tend to consume sufficient quantities of vitamins and minerals in our food.

Although their biological roles are frequently similar, vitamins and minerals have a fundamental chemical difference. Vitamins are organic molecules, meaning they contain carbon, whereas minerals are inorganic nutrients. Because vitamins are organic, they are more fragile, easily destroyed by heat and other chemical or physical extremes. Minerals, on the other hand, are elements, so they can’t be broken down further or lose their chemical identity. They stay in your body until they are excreted. In fact, the only way they can be lost is if they are leached away—such as when minerals are leached from food into the water as the food is cooked and the water isthen thrown away. Seventeen minerals have been identified that are essential to the human diet. They are described in FIGURE 22-14.

Thirteen vitamins essential to humans, also described in Figure 22-14, have been discovered. They fall into two groups, based on whether they are soluble in fat or water. The water-soluble vitamins include eight vitamins that are part of the vitamin B complex, plus vitamin C. There is some variation among species in the ability to manufacture (rather than needing to ingest) vitamins. Cats and dogs, for instance, can make vitamin C and do not need to consume it.

There are four fat-soluble vitamins: A, D, E, and K. Because they are stored in fatty tissue and the liver until they are needed, they don’t need to be consumed as regularly as water-soluble vitamins. Also, because excess water-soluble vitamins can be removed by the kidney and excreted in urine, they are less likely to reach toxic levels than fat-soluble vitamins.

Currently, more than half of the U.S. population takes regular vitamin supplements (FIGURE 22-15). Usually, taking vitamin supplements is a costly but harmless behavior. The consumption of increasing amounts of vitamins often just leads to a plateau of maximum benefit, after which greater consumption has no additional benefits. Occasionally, however, taking vitamin and mineral supplements is both costly and harmful: in many cases, above a certain point, additional consumption of fat-soluble vitamins can lead to toxicity and cause serious health problems. Excessive consumption of vitamin A, for example, can lead to hair loss in men, while over-consumption of vitamin D can lead to growth retardation. Liver damage, too, is a common result of excessive vitamin and mineral consumption. Moreover, research has definitively discredited claims that vitamin E supplementation slows or prevents aging or improves physical performance, and no supplement has been demonstrated to “relieve stress”—despite the extravagant claims of marketers.

Most people in the United States receive all of the nutrients they need from the foods they eat and have no need to take vitamin and mineral supplements. Under special circumstances, however, some individuals may benefit from a nutritional supplement.

• Women who lose unusually large amounts of blood during menstruation may need iron.
• Post-menopausal women and those allergic to milk may not get enough calcium in their diet to prevent bone degeneration.
• Pregnant and breast-feeding women may need additional vitamins and minerals to support a developing fetus or rapidly growing infant.
• Pregnant women, or women who may become pregnant, may need additional folate, which helps prevent neural tube defects.
• People on extremely low-calorie diets may need vitamin and mineral supplements.
• People with limited consumption of milk or sun exposure may need additional vitamin D. Because of insufficient levels of ultraviolet energy from the sun at latitudes above 42° (in the United States, a line extending approximately from the northern border of California across to Boston), individuals in these regions are unable to produce sufficient vitamin D from sun exposure alone.
• People with absorption problems (such as when taking antibiotics, or having an infection, or following surgery) may need vitamin and mineral supplementation.

Individuals who do not fall into these groups, however, generally get all of the essential vitamins and minerals simply by eating a varied diet, rich in nutritious foods.