Blog | Tuesday, February 9, 2010

Vitamins in a Nutshell


This post by Davis Liu, MD, originally appeared at Better Health.


Some patients love their vitamins, spending hundreds to thousands of dollars annually. At times, they will even forgo proven medical therapy. As more Americans go without health insurance coverage while others face higher office visits and copays, increasing numbers of patients are seeking alternative, natural therapies instead of medical care. Are vitamins really the scientific breakthrough and secret that doctors refuse to recommend, or are they simply marketing hype? As any medical school student will tell you, the correct answer to any question is: it depends.

Vitamins! by bradley j via FlickrFor certain groups, pregnant women, patients with macular degeneration and vegetarians, vitamins and minerals may be recommended as research finds them helpful. Prenatal vitamins have more folic acid, which has been found to decrease the risk of neural tube defects in the fetus. Vegetarians may need to supplement their diet with vitamin B12, iron, and vitamin D, which are absent in their food choices.

Patients with a history of gastric bypass should be on a multivitamin that contains iron and vitamin B12. The surgery, which is used to cause weight loss in morbidly obese patients, can bypass part of the digestive tract responsible for absorbing these nutrients.

Women of all ages should take calcium and vitamin D to improve bone density to decrease their future risk of osteoporosis. This means at least 1,000 mg of calcium daily and vitamin D 800 to 1,000 international units (IU) per day. Women over 50 should be taking 1,500 mg of calcium/day. A common misconception is that a multivitamin has enough calcium. It doesn't! A typical multivitamin has about 45 mg of calcium (a glass of milk is about 300 mg).

Aside from these individuals, the result of us with a balanced diet should get the right amount of vitamins and minerals. You don't need the large mega-dose vitamin packs found at your local warehouse store or nutritional shop. Not only are they expensive, but also unproven.

If you still feel like you can't get through life without taking vitamins, then at least be aware of the following:

Limit the amount of fat soluable vitamins that you ingest, specifically vitamins A, D, E and K. Unlike water soluable vitamins, of which excess amounts are excreted by the kidneys, fat soluable vitamins can build up levels in the body.

For vitamin A, toxic levels begin after ingesting more than 50,000 IU daily. Upper limit of tolerable intake (what is considered the upper limit of normal but still safe) is 10,000 IU. Recommended daily allowance is 3,000 IU.

For vitamin D, the upper limit is 2,000 IU. The current daily allowance is 600 IU. A new recommendation is expected in May 2010 by the Food and Nutrition Board. Vitamin D is obtained by the skin via sunlight exposure. With people indoors more often than generations ago and possibly the increased use of sunscreen, doctors are seeing more cases of vitamin D deficiency. Your doctor may prescribe a weekly dosage of 50,000 IU weekly for three months to replace. Low levels of vitamin D can cause muscle pains, so if a constant problem, ask your doctor to check your levels. (Cod liver oil, incidentally, is rich in vitamin D and is probably why growing up in Canada I had a lot of it during the winter. Ick.)

For vitamin E, the recommended dosage is 22.4 IU with the upper limit of tolerable intake no more than 1,500 IU. Some research suggested that there was increased mortality for those individuals taking more than 400 IU per day. Because of its antioxidant properties, researchers thought taking more was better. It wasn't.

For vitamin K, found in green leafy vegetables, it is the only fat soluable vitamin where there is no defined upper limit for toxicity. Overdose of vitamin K is rare.

Am I against vitamins? Of course not. For some patients, in fact, they are recommended. What I am against is, however, having individuals spend their hard-earned money for therapies that aren't proven. Note that the FDA, under current legislation since 1994, has no oversight over nutritional supplements.

This is why all vitamin package inserts have the following statement:
* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Want to live well? A better insurance policy than vitamins is to not smoke, perform regular physical activity, take in five servings of fruits and vegetables, and possibly drinking alcohol in moderation (as a doctor I can't recommend that, but if you drink already, it might be ok). Researchers found individuals who did all four behaviors added 14 years to their lives. Why don't more of us these activities? They all take some effort. Swallowing vitamins are quicker and easier.

If I still haven't convinced you not to take unnecessary vitamins, then at least check with your doctor before stopping your medical therapies or adding supplements that can interfere with your treatment.

Finally, please avoid colon or total body cleanses. Sounds natural and healthy, but again aren't required. A product found at a large nutritional chain's special "anti-oxidant" formulation basically consists of fruits, vegetables and fiber. You can do that yourself for a lot less, and it probably tastes better too.

This post originally appeared on Better Health, a network of popular health bloggers brought together by Val Jones, MD. Better Health's mission is to support and promote health care professional bloggers, provide insightful and trustworthy health commentary, and help to inform health policy makers about the provider point of view on health care reform, science, research and patient care.