Should you take a daily multivitamin?

Short answer

Some people with special diets or medical conditions need to take vitamins daily. However, as long as you eat a balanced diet of good-for-you foods, the human body is very good at taking in all the nutrients you need.

Evidence shows that taking a daily multivitamin will not significantly benefit your health. However, if you still want to take one, this usually poses little to no harm. You should understand that the Food and Drug Administration does not regulate or test over-the-counter supplements and vitamins. This allows many vitamin manufacturers to make false claims about their benefits.

Long answer

What exactly are vitamins and minerals? Vitamins are molecules or groups of molecules that your body needs in small amounts to function. They must be obtained from diet, as your body cannot create them.

Vitamins help build bones, maintain the immune system, and regulate cell growth. If you develop a vitamin deficiency, you could develop diseases that we rarely see in the first world, such as scurvy (yes, like a pirate) and rickets (yes, like Tiny Tim).

Minerals are inorganic substances such as iron, calcium, and sodium, which your body also needs in small or trace amounts to function properly. They are helpful for building bones, making hormones, regulating your heartbeat, and supporting healthy muscles and brain function.

Many Americans take a daily multivitamin supplement, thinking that it will prevent chronic diseases or help them live longer, but the most current evidence shows that this is not the case. For the average person, multivitamins have not been found to be effective in preventing cancer, cardiovascular disease, dementia or recurrent infections.

So maybe there is no benefit from taking a daily multivitamin, but is there any known harm? For most people, probably not, but consider the following:

Typically, multivitamins are OK, but many supplements can interact with other prescription and over-the-counter medications.
Many vitamins are water-soluble; generally, your body will “filter out” any excess amounts (I.E., they come out in your urine). But some vitamins (predominantly A, D, E and K) are fat-soluble and can build up in your body, and they can wreak havoc if you reach toxic levels.
While the FDA can investigate supplements and vitamins, they do not undergo any pre-market regulation to prove that they are safe, effective, or live up to their claims. Do not be fooled by a product stating that it is "natural." This is essentially meaningless labeling, and keep in mind that mercury, cocaine, arsenic and cow feces are also in the category of "natural."
A few organizations offer some level of optional regulation. If you see seals from one of these companies, it means that the product has passed the organization’s quality tests for content, strength and contaminants. These “seals of approval” do not mean that the product is safe or effective, but they provide assurance that it contains what is actually on the ingredient list and does not contain harmful contaminants.