How Multivitamins Can Harm Your Health

When it comes to vitamins, don’t fall into the trap of thinking “the more the better.” Gone are the days when everyone was advised to take a multivitamin, said Leo Galland, MD, an internist and founder of PillAdvised (, an online resource for information about medications and supplements. It’s better to get nutrients from dietary sources as much as possible — and it’s now clear that some of the ingredients in these pills may be unnecessary or even harmful.

Last week (see Daily Health News, December 23, 2010, “Mineral Supplements Can Be Toxic”), Dr. Galland told us about the benefits and considerable risks of taking certain minerals, either alone or as part of a multivitamin. I invited Dr. Galland to continue the discussion today by evaluating the most commonly used vitamin supplements. Are any of them dangerous… and do you really need them? I suspect that some of what you read will surprise you.

Folic acid is a synthetic “previtamin” that the body converts into the vitamin folate. It’s important for the health of the brain, nervous system and immune system… for normal cell growth and normal fetal development… and for the prevention of cancer. Though folate is found naturally in some foods (including liver, green leafy vegetables and citrus fruits), most people don’t get enough of it in their diets.

The dilemma: We need folate, but taking supplements made of the synthetic form (folic acid), even in doses as low as 400 mcg (the amount prescribed by OB-GYNs during pregnancy), has been linked to several types of cancer. Too much folic acid can mask symptoms of vitamin B-12 deficiency and can even lead to permanent nerve damage if the B-12 deficiency is not corrected. Also, certain common drugs — including nonsteroidal anti-inflammatory drugs (NSAIDs) and some medications for inflammatory bowel disease — can interfere with the body’s ability to convert folic acid to folate.

Dr. Galland’s advice: Far better than folic acid is to take 500 micrograms (mcg) a day of L-methylfolate, a form of folate that circulates in the blood and is therefore more physiologically accessible. This is most particularly important for adults over age 50.

Vitamin A deficiency, which can cause impaired immunity, night blindness, susceptibility to infection and rough, dry skin, is quite common. The body creates vitamin A from beta-carotene (found in orange and red vegetables and fruits, liver and whole milk), but some people don’t get enough from their diets. In other folks, a vitamin A deficiency is caused by their inability to properly absorb vitamin A or to convert it from beta-carotene.

The dilemma: Vitamin A supplements have the potential to cause a host of problems, including headaches, bone loss, yellow or orange skin, rash, loss of eyebrows and liver disease. Also, supplementing with beta-carotene can increase the risk for lung and colon cancer in people who are or were heavy smokers. These problems can arise in several ways: When very large doses of vitamin A or beta-carotene are eaten… when other complementary antioxidant vitamins and minerals aren’t consumed in sufficient quantities to balance and leverage the benefits of vitamin A or beta-carotene… or when lifestyle choices (such as heavy smoking) distort the benefit of the vitamin.

Dr. Galland’s advice: If you have any clinical signs of vitamin A deficiency (listed above) and think you could benefit from a beta-carotene supplement, look for one formulated with other carotenoids (often called “mixed carotenoids” on product labels). Or, if your blood test shows that you have a low vitamin A level, your doctor may prescribe a form of the vitamin called retinol, which also circumvents these problems.

Vitamin D is all over the news these days. This vitamin helps strengthen the immune system and prevent cancer and ensures that the body properly absorbs calcium, while a deficiency of vitamin D is linked to a variety of health problems, including certain autoimmune disorders (such as type 2 diabetes), chronic metabolic and systemic diseases, and an increased risk for multiple sclerosis. Our bodies manufacture vitamin D when the skin is exposed to sunlight — which is problematic at this time of year for those of us living in the northern hemisphere, since sunlight is in short supply. Another problem: Aging reduces the skin’s ability to produce vitamin D from sunlight. For these reasons, most Americans need supplemental vitamin D.

The dilemma: Excessive vitamin D supplementation brings its own list of problems, some quite serious — including kidney damage and leaching of calcium from bones into soft tissue. Plus, vitamin D supplements may cause problems for people with diabetes (talk to your doctor) and should not be taken by people with high calcium levels, kidney stones or sarcoidosis, a disease where scar tissue is deposited in multiple sites throughout the body.

Dr. Galland’s advice: Do not take vitamin D in doses higher than 2,000 IU per day without your doctor’s approval. Take vitamin D-3, the form that’s absorbed best, after your largest meal of the day.

Vitamin E was once a wildly popular supplement, thought to have many potential benefits, including prevention of heart disease and cancer. While those claims have been called into question, research does show that vitamin E can help reduce risk for recurrent strokes in people with diabetes.

The dilemma: Most people get only a minimal benefit from vitamin E supplementation, while excessive amounts or the wrong type of vitamin E has the potential to do some serious damage. Studies show that vitamin E supplements can increase the risk for heart failure in people with heart disease, mainly by depleting the body of coenzyme Q10, which is needed for proper coordination of the pumping mechanism.

Dr. Galland’s advice: If you wish to take supplemental vitamin E, choose the natural form of a “mixed tocopherol” product (labeled “d” — not “dl”) that contains alpha, beta, gamma and delta tocopherols — this is closer to what you’d find in food. No one should take vitamin E doses exceeding 100 IU per day (unless under the advice of a physician), and vitamin E should not be taken at all by anyone who takes statin drugs. Research has demonstrated that statins inactivate the antioxidant effects of vitamin E and that vitamin E may interfere with the therapeutic effect of statins, so people who take both may end up getting the benefit of neither.

Be Careful About Taking Vitamins

Vitamins should not be taken indiscriminately, cautions Dr. Galland. All the vitamins listed above are frequent components in multivitamins in amounts that can be problematic for some people, so it is vitally important to read labels carefully even for seemingly safe multivitamins. Don’t take a multivitamin if it contains ingredients that you don’t need, and stop taking individual vitamins if you are getting sufficient quantities of them in your multivitamin. And remember, these are all reasons why it is so important to have an expert in nutritional medicine on your health-care team.