Vitamins and Minerals

Small Stuff, Big Action

The scientific definition of a vitamin is "an organic compound, not a lipid or amino acid, required in very small amounts for essential functions in the body." Anything that’s organic—from mulch and tree trunks to toenails and earlobes—contains the element carbon, the same element that’s found in every vitamin. Lipids (fats) and amino acids are also organic, but they are not vitamins.

The customary means of getting vitamins into our bodies is to eat plants or animals that make or store these compounds. Plants use sunlight, air, water, and nutrients from the soil to synthesize folate in their leaves. Some plants and animals make their own vitamin C. Vitamins can also be synthesized from organic compounds in a laboratory. Thus, when you buy a vitamin supplement, you might be getting compounds that have been put together by plants and animals, or you might be getting identical, look-alike compounds that have been assembled in a laboratory.

Minerals are inorganic, but these, too, are available from organic sources. Plants absorb minerals from the ground, and animals get them from the plants they eat, so the root source of all minerals is the Earth.

By definition, anything officially labeled a "vitamin" is in some way absolutely necessary to human health. "If a substance found in food has a defined biochemical function in the human body, it is considered essential," says Forrest Nielsen, Ph.D., director of the U.S. Department of Agriculture (USDA) Human Nutrition Research Center in Grand Forks, North Dakota. It may take many years of research, however, before scientists know whether a component is essential, he adds.

Essential nutrients may be parts of hormones. The trace mineral iodine, for instance, is needed to manufacture thyroxine, the thyroid gland’s major hormone. Nutrients may also be needed to break down food for energy, as many of the B vitamins are.

Nutrients can also break down wastes that are subsequently eliminated from the body. The trace mineral manganese serves this role, converting the toxic ammonia that we form in our bodies into urea, which is excreted in urine.

Some nutrients appear to be essential even though their biochemical functions have yet to be defined, Dr. Nielsen says. Chromium, nickel, and boron are examples. Arsenic, a substance that we label as poison, is one of the possibly essential nutrients under investigation, since we don’t know why our bodies need it.

It’s likely that more nutrients will make the "essential" list as research continues. "There are a lot of gray areas left to explore," says Gerald Combs Jr., Ph.D., professor of nutrition at Cornell University in Ithaca, New York. He cites omega-3 fatty acids and the amino acid carnitine as two examples. "Now we realize that omega-3 fatty acids are required for neurological development and eye development in infants," says Dr. Combs. "Some experts also think that carnitine may be required for infants under some circumstances."

As we develop better technology, we can scrutinize the additional properties of vitamins and minerals even more closely, Dr. Combs adds. "We can measure things we couldn’t even conceive of earlier." Within the last four decades, for example, the ability to measure zinc has improved tremendously. "Twenty-five years ago, we thought there were five or six zinc-containing enzymes because that’s all we could measure," Dr. Combs observes. "Now we know there are two or three hundred, simply because we can detect tinier and tinier amounts."

Getting Your DVs

Although each of us has somewhat different needs for vitamins and minerals, we all need a certain basic supply of nutrients. Based on research, experts have drawn up a set of nutrition guidelines that are universally used as a standard of measurement by the federal government. The nutrition information that you’ll find on any packaged food—and on most bottles of vitamins and minerals—is based on those guidelines.

Wherever you see the abbreviation DV, it stands for Daily Value. The DV column on a label lists the percentages of the DV for vitamins or minerals in a serving of a food or in a single dose of a supplement, based on an intake of 2,000 calories a day. The DV for vitamin C, for instance, is 60 milligrams, so a supplement containing 60 milligrams has 100 percent of the DV. The label of a supplement containing 30 milligrams of vitamin C would indicate that it has 50 percent of the DV.

Since each of us has different needs, your vitamin C requirement might be higher than the DV if you’re older, if your immune system needs some boosting, or if you’re recovering from an infection. Smokers, for instance, have an enhanced risk of many kinds of diseases, so the recommended dose for them is 100 milligrams, more than 160 percent of the DV that applies to most nonsmokers.

Age differences, sex differences, and stage of life can also affect your nutrient needs, meaning that your actual daily requirements for vitamins and minerals may vary from the DV for many reasons. Women generally need more nutrients when they’re pregnant or breastfeeding, which is understandable enough, since they are essentially eating for two. For both men and women, vitamin and mineral requirements are likely to change somewhat with age, and very active or athletic people are likely to need more than those who are less active. All of these factors have an impact on individual nutrient requirements.

Some of these differences are readily apparent. Consider the needs of infants. Per pound of body weight, nutrient needs are highest when an infant is growing rapidly, as it does during the first year of life, says Kathryn Kolasa, Ph.D., professor of nutrition education at East Carolina University School of Medicine in Greenville, North Carolina. Nutrient needs are also high during teenage growth spurts, usually from ages 12 to 20 for boys and 10 to 18 for girls.

A Little Something Extra

To help us get our DVs of vitamins and minerals as well as meet other basic nutritional requirements, nutrients are routinely added to foods that many of us eat nearly every day. When this is done, the foods are called fortified or enriched. This program, regulated by the federal government, has been highly successful in helping to eliminate severe nutritional deficiencies.

In the United States, iodine has been added to salt since 1930. Before then, in areas where people had little or no iodine in their food supplies, it was fairly common to see the medical condition called goiter. An enlargement of the thyroid gland, goiter is a direct result of iodine deficiency, says Paul Lachance, Ph.D., professor and executive director of the Nutraceutical Institute at Rutgers University in New Brunswick, New Jersey.

Slightly less than ½ teaspoon of iodized salt a day provides enough iodine to prevent goiter. Non-iodized salt, such as kosher salt, is still available, but manufacturers are required by law to offer the iodized version as well. People are so used to buying iodized salt that goiter problems have been virtually eliminated.

Vitamin D is another cause célèbre of the government’s nutrition program. Since the 1940s, vitamin D has routinely been added to milk to help prevent childhood rickets, a disease that causes bones to become deformed or soften. This fortification program helped make childhood rickets virtually unknown in the United States, Dr. Lachance says.

In a quart of fortified milk, you’re supposed to get 400 international units (IU) of vitamin D, which is the DV. Not all milk contains this amount, and fat-free milk seems to be skimpiest, according to a study from researchers at Boston University. Sadly, vitamin D deficiencies are still prevalent in middle-aged and older adults, leading to problems that result in the softening of the skeleton (osteomalacia) or loss of bone (osteoporosis). Still, the vast majority of young Americans are getting enough vitamin D from milk and other sources to ensure that they aren’t at risk for childhood rickets.

Vitamin A is also added to milk, particularly reduced-fat, low-fat, and fat-free milk. In the 1940s, when this vitamin was found to improve immune response and correct some vision problems in children and women, the government began requiring that it be added. Whole milk naturally contains some vitamin A—about one-third of the DV in a quart—but extra vitamin A is sometimes added. Most powdered milk contains vitamin A, along with vitamin D.

Since 1942, white flour, cornmeal, and polished (white) rice have been enriched with three B-complex vitamins—thiamin, riboflavin, and niacin—and with iron. In 1998, folic acid was added to the list of required fortifications. Whole-wheat flour is not enriched because it naturally contains these and other nutrients.

Even with this fortification program, we can’t take all of these nutrients for granted, Dr. Lachance says. While fortification has made serious deficiencies much less likely to develop, iron deficiency is still the most common in the United States, he says. It’s also possible that you’re not getting enough vitamin A or D if you don’t drink much milk.

Deficiency Detection

When someone is deficient in an essential nutrient, some symptoms are sure to crop up after a while. Health problems ensue. Fatigue, muscle weakness, irritability, reduced resistance to infection, poor healing, and slowed growth, are common to many vitamin and mineral deficiencies.

Despite these well-known signs, the detective work isn’t easy. , for example, is a condition that’s characterized by many of the symptoms of overall nutrient deficiencies—particularly fatigue and muscle weakness. It occurs when there’s a reduction in the number of red blood cells, but there are many possible causes of that reduction. In some people, is caused by iron deficiency. Others may display symptoms of other kinds of because they’re short on vitamins A, B₆, B₁₂, Sustenance from Sunbeams— And Other Sources

Most of our nutrients come from food, but there are notable exceptions.

Given enough exposure to the sun’s ultraviolet rays, our bodies convert one kind of fat in the skin to vitamin D. Sunlight has traditionally been considered health-reviving for that reason.

Getting adequate vitamin D helps prevent crippling bone deformities like rickets, which began to appear more than 200 years ago as northern European countries became industrialized. With more people living in cities and more cities darkened by the overhang of smoke from industrial production, sunlight was fighting a losing battle with manmade interferences.

A Polish doctor named Sniadecki first made the connection between the need for sunlight and the bone diseases that appeared like a slow-moving epidemic in these industrialized areas. He advised parents to take their rickets-ridden children into the country, or at least carry them into the sunlight as often as possible. He had no idea what healing power was in the rays, but whatever it was, he surmised, these children needed it.

There are also instances in which lifestyle does the doctoring. In countries such as India, people who are strict vegetarians suffer from shortages of vitamin B₁₂ in their diets. Some of the lack is made up from an unusual source—bacteria in food. Unappetizing as it seems, certain bacteria synthesize vitamin B₁₂. Our bodies need only a tiny amount of this vitamin, and bacteria make enough to compensate.

Some forms of yeast, which is actually a living fungus, also synthesize B₁₂. Since this is especially true of brewer’s yeast, a strict vegetarian who drinks beer may have a ready source of this vitamin, says Gerald Combs Jr., Ph.D., professor of nutrition at Cornell University in Ithaca, New York. (Of course, the average beer contains only 0.06 microgram of B₁₂, so even if vegetarians have an occasional cold one, they must take supplements to get the Daily Value of 6 micrograms.)

Extra minerals can also be obtained in some unusual ways. Take iron, for instance. The iron in cast-iron pots or skillets is actually transferred to food when we cook with those utensils. Although the transfer might seem insignificant, it can increase the iron content of foods by two to six times.

The skins of fruits and vegetables, especially root vegetables like carrots and potatoes, are also good mineral “supplements” because trace minerals are concentrated in the pores of the skins. True, you need to wash these foods before eating them to remove unwanted bacteria and pesticides, but you’ll still get some minerals once you start munching.