Vitamin Supplements: Are They for Everyone?
Last reviewed and revised October 23, 2012
By Robert H. Shmerling, M.D.
Better take your vitamins they're good for you!
When I was a kid, I remember hearing these words from my mother and in TV commercials. It seemed like good advice, yet not all my friends were taking vitamins, and they seemed healthy. That got me wondering: Are they really good for you? Which ones are best and how much is enough? Could they be harmful?
In recent years, recommendations to take various vitamins (and other supplements) are so commonplace that I often see patients who are taking six, eight or even more vitamins each day.
The term "vitamin" comes from "vita" (meaning life) and "amine" (a type of compound that includes some vitamins). There are 13 well-accepted vitamins (see below). Vitamins are not the same as essential minerals, which are also vital to life. Vitamins are compounds or molecules, while minerals are made up of a single element.
By definition, everyone needs vitamins. And yet, for many people perhaps most people taking a daily multivitamin is a harmless but, medically speaking, wasteful expense and effort. One notable study found that average, healthy people taking a multivitamin each day were no healthier and lived no longer than healthy people who took no vitamins.
Because vitamins are needed only in small amounts, most people get more than enough from what they eat. For some, however, getting supplemental vitamins is truly vital, either because of people's choice of foods or because they are unable to absorb and digest one or more vitamins.
Then again, taking too much of certain vitamins can actually be dangerous. The trick is sorting out who should take vitamin supplements to avoid illness and for whom it is unnecessary.
Most experts and textbooks divide vitamins into those that dissolve readily in water and those that dissolve in fat. This is helpful because the body handles water and fat quite differently.
Water-soluble vitamins are readily absorbed from the intestine and used by the body; any extra tends to be removed quickly in the urine. Most must be replenished regularly from dietary sources.
Fat-soluble vitamins offer more of a challenge. Certain people have medical conditions that cause problems with absorbing fat-soluble vitamins. Despite adequate dietary intake, they need extra. On the flip side, fat-soluble vitamins are stored in body tissues (such as the liver) and released very slowly over time. As a result, taking too much can be dangerous.
The 13 major vitamins include the water-soluble vitamins (thiamin, riboflavin, niacin, B6, folic acid, B12, pantothenic acid, biotin and C) and the fat-soluble vitamins (A, D, E and K).
When there is clear evidence of a vitamin deficiency, treatment decisions are generally easy. But when it comes to routine use of vitamin supplements, experts have come to different conclusions. And people often ignore expert recommendations anyway, taking vitamins that no medical provider has suggested and not bothering to take ones that may have been suggested as a preventive measure.
There is reasonable scientific evidence to support the regular use of certain vitamins by:
Anyone with a specific vitamin deficiency should take measures to replenish it. Deficiencies may be detected when symptoms develop or when laboratory abnormalities are noticed in routine testing. Some of the more common vitamin deficiencies include:
If you have any of these symptoms, talk to your doctor about their cause, including the possibility of a vitamin deficiency.
While intake of vitamins through diet or supplements is vital to life itself, there are limits. Consider the following potential consequences of long-term "megadose" vitamin therapy:
Some vitamins may interact with medications you may be taking. An important example is vitamin K, which counteracts the blood thinner warfarin (Coumadin). If you are taking warfarin to prevent stroke, taking extra vitamin K could offset that benefit, increasing your risk of stroke.
In the absence of a specific disease or condition that warrants it, there is risk without clear benefit related to taking high doses of vitamins. Even "regular" doses of some supplements may impair health: Studies have noted that the use of beta carotene (a precursor of vitamin A) is associated with a higher risk of cardiovascular disease and some cancers.
Increasingly, experts are recommending that all adults take a multivitamin each day as "insurance" against vitamin deficiency. Folate also may lower risk of breast and colon cancer and birth defects. Vitamin D may lessen the risk of osteoporosis and osteomalacia.
For women who might become pregnant, experts recommend 400 micrograms per day of folic acid. Some recommend 800 micrograms a day for women who are specifically trying to become pregnant.
It's likely that ongoing research will spell out which vitamin supplements are most important and who should take them. Until then, things are likely to remain pretty confusing.
Consumers are deluged with recommendations to take lots of vitamins. Much of this promotion comes from people or companies trying to sell their products, or from studies that may be preliminary or even contradict other research.
It's enough to make your head spin and there's no good vitamin you can take for that!
Do you really need to take your vitamins? Probably not, especially if you are healthy and already get at least five servings of fruits and vegetables each day.
But if you are concerned that your diet might not meet your vitamin needs, change your diet and take a single daily multivitamin. It should be inexpensive and contain 100% of the recommended daily allowance of the 13 major vitamins. While this might not be absolutely necessary, the minimal cost and risk might just be worth the peace of mind.
Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.