Vitamins: Too Much of a Good Thing?

Feb. 23, 2004 -- Popping a vitamin pill seems like an easy cure-all. But this once-a-day health ritual might actually be the cause of what ails you.

Experts warn toxic doses of four common nutrients — iron and vitamins A, D and B6 — can be easily consumed through careless use of everyday vitamin pills.

Click for Recommended Amounts of Four Key Nutrients

"People think there can't be a downside to vitamin and mineral supplements. After all, they're sold over the counter and contain the same vitamins found in foods," says Dr. Lora Sporny, professor of nutrition at Columbia University in New York City.

Medical experts agree taking a daily vitamin pill is safe for most people. "But in concentrated doses some vitamins and minerals can have very different effects on the body," cautions Sporny. "They can have pharmacologic, drug-like effects."

Too Much of a Good Thing

The one mineral and three vitamins found to cause health problems in large doses — iron and vitamins A, D and B6 — are all essential to health. Diets lacking them can cause a host of health problems, including anemia, dermatitis, skeletal deformities and eye damage.

But if a little is good, more is not always better. Popular grocery items like breakfast cereals, bread, nutrition bars, fruit juices and milk are now fortified with high doses of vitamins and minerals.

"We're seeing an over-fortification of the food supply," says Sporny. "Some breakfast cereals offer 100 percent of the recommended doses of vitamins and minerals in one serving — about one cup. And people are eating servings two to three times that large, then pouring milk fortified with vitamins A and D over that cereal."

Sporny adds: "I fear that as we move forward we may see more nutrient toxicity. It's a prescription for some very serious problems."

Children, Others at Risk

While all consumers are at risk of vitamin and mineral overdose, some groups are of particular concern.

"Children, because of their smaller size, can get into trouble with lower amounts than adults," explains Dr. Daniel E. Rusyniak, medical toxicologist with Indiana University School of Medicine in Indianapolis, Ind.

In particular, high doses of iron have been blamed for serious health problems among children. In an eight-year study conducted at Georgetown University Hospital in Washington, D.C., iron supplements were the single most frequent cause of death from accidental overdoses among children.

One reason for the high number of deaths, researchers decided, is these pills often look like candy.

Iron-Rich Blood

Another vulnerable group are those with hemochromatosis, the most common genetic disorder in the United States, affecting one in 200 Americans. With hemochromatosis, the intestines absorb too much iron into the blood stream.

Because hemochromatosis is often undiagnosed or misdiagnosed, people with the disorder are especially susceptible to iron toxicity.

But iron toxicity can also be caused by a diet high in iron, and most men and post-menopausal women need no iron supplements at all.

The most typical symptoms of iron toxicity are fatigue and joint pain, as well as impotence, loss of sexual desire and depression.

"Iron has the highest toxicity typically seen from vitamin and mineral overdosing," says Rusyniak. "Larger doses can cause coma, low blood pressure, liver failure, scarring of the stomach and death."

Vitamins: A Poison Pill?

Part of the problem with vitamins A and D is that they are fat soluble and large doses can build up in body tissue. Most vitamins, by contrast, are water soluble, and large doses are simply passed out of the body through the urine.

"Vitamin A can easily be toxic," says Sporny. "Just two to three times the RDA can increase the risks of hip fracture and birth defects. And now, there's some debate that the amount of vitamin A found in a multi-vitamin might even be too much, especially for women trying to conceive and for an older population."

Like many nutrients, the amount of vitamin D needed varies with age, and people over 70 may need more. "Taking some vitamin D is OK for an aging population," says Sporny, "but too much vitamin D can cause damage to blood vessels, eye tissue and kidneys."

Though vitamin B6 is water soluble, medical experts have found excessive doses from vitamin supplements often cause nerve damage.

So are vitamin and mineral supplements dangerous? Don't go emptying your medicine cabinet just yet.

"In moderation, most vitamin and mineral supplements are perfectly safe," says Rusyniak, "but care should be exercised when taking multiple supplements containing the same vitamins and minerals."

Sporny also advises a common-sense approach. "A basic multi-vitamin and mineral supplement, specific to your age and sex group, can be a good addition to your diet. But taking vitamin supplements willy-nilly without any medical supervision can exacerbate problems."