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Vitamins and Minerals
Vitamins—unlike protein, carbohydrates, and fat—are not a source of energy. They are catalysts for the biochemical reactions that take place in the body. Since vitamins are not manufactured by the human body, we must eat foods that supply them, or take vitamin supplements.
Like vitamins, minerals are needed for many bodily functions, especially as building blocks for tissue and as regulators of metabolic processes. We need different kinds of minerals for good health and growth, some in relatively large quantities and some, known as trace minerals, in minute amounts.
The minerals that are needed in higher amounts are calcium, potassium, sodium, magnesium, and phosphorus. The trace minerals include iron, copper, zinc, manganese, chromium, selenium, vanadium, and molybdenum.
If we all ate the recommended amounts of fruits, vegetables, and other nutrient-rich foods, we probably would not need most vitamin and mineral supplements. The Dietary Guidelines for Americans advise us to get our vitamins and minerals directly from foods because foods also contain more than nine hundred naturally occurring substances—such as fiber, carotenoids, flavonoids, polyphenols, anthocyanins, isoflavones, resveratrol, and protease inhibitors, the phytonutrients described earlier—that may protect us from chronic health problems.
That said, most of us don’t eat such healthful diets, and as we age and our appetites diminish, we can find it hard to consume enough food to provide the necessary nutrients. On top of that, most of the fruits and vegetables sold in supermarkets are transported long distances and stored before being put on sale. That gap from field to table results in nutrient loss and, in some instances, may require that we take a multivitamin and/or mineral supplement and consume certain fortified foods.
Vitamins are either water-soluble or fat-soluble. The water-soluble vitamins—C and the B family—are not stored in the body, so we must eat foods that provide them every day. The fat-soluble vitamins—A, D, E, and K—are stored in the fatty tissues and are absorbed and used by the body only if we eat appropriate amounts of fat with our meals.
Because of their low intake of protein and because they don’t absorb it well, many older people suffer from a deficiency of B12, which causes anemia and neurologic disorders. The Dietary Guidelines recommend that people over fifty consume foods to which vitamin B12 has been added, such as fortified cereals, or take the crystalline form of vitamin B12 supplements.
By age eighty, 35 percent of men and women suffer from a wearing out of the intestinal lining. This causes lower levels of acid secretion, leading to a decreased absorption of folic acid, iron, calcium, and vitamins B6 and B12. To counter this, obtain folic acid by eating uncooked leafy vegetables, yeast, and fruits daily, supplemented with 400 micrograms of folic acid.
VITAMIN A
Liver, fish oils, eggs, and whole milk are sources of vitamin A, but the best sources (free of cholesterol and saturated fat) are carrots, sweet potatoes, and dark leafy green vegetables. Plants don’t actually contain vitamin A itself but, rather, carotenoid precursors that the body can turn into vitamin A. Vitamin A is important for good eyesight and a strong immune system, but people should not take supplements that contain vitamin A itself because it can build up to a toxic level in the liver. On the other hand, beta-carotene and other carotenoids are safe at any dose.
VITAMIN D
Vitamin D is necessary for our bodies to absorb calcium from food, to strengthen bones, and to prevent fractures. Recent