Should You Take a Multivitamin?

Walk into any store and you will see a wall of multivitamins. Some promise energy. Some promise better immunity. Should you take one? Here is what the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) says.

What is a multivitamin?

A multivitamin/mineral supplement, or MVM, has a mix of vitamins and minerals. ODS says there is no standard MVM. Each company picks what goes in and how much. Some have the amounts you need in a day. Some have much more. Some add herbs or other ingredients.

The most important point from ODS is this: MVMs cannot take the place of eating a variety of foods. Food also gives you fiber and other helpful things that a pill does not.

Do they prevent disease?

ODS says scientists have studied whether MVMs change the risk of cancer, heart disease, bone loss, lung problems, mental health conditions and early death. Most studies found little or no effect. ODS says it is unclear whether an MVM affects cancer risk. It also says MVMs appear to have little or no effect on heart disease risk.

Why is it so hard to know? Studies use different products. Also, people with healthier lifestyles are more likely to take MVMs. That makes the benefit hard to measure.

Who might need one?

ODS says people might consider an MVM if they:

• Do not get enough vitamins and minerals from food alone
• Are on a low-calorie diet
• Have a poor appetite
• Avoid certain foods, such as strict vegetarians and vegans

Some life stages call for extra care:

• If you might become pregnant: 400 micrograms a day of folic acid from fortified foods or supplements lowers your baby's risk of birth defects of the brain and spine.
• If you are pregnant: A daily prenatal MVM can help you get enough folic acid, iron, iodine and vitamin D. Your doctor may suggest more.
• If you are over 50: Get enough vitamin B12 from fortified foods or supplements, because your body may not absorb enough B12 from food.
• If you are 60 or older: A few studies found an MVM might help maintain thinking and memory skills.

Can they be harmful?

ODS says a basic MVM is unlikely to harm your health. But it is possible to get too much of some nutrients, such as iron, vitamin A, zinc, niacin and folic acid. This is more likely if you eat fortified foods like some cereals or take other supplements. Add up everything you take.

Smokers, and maybe former smokers, should avoid MVMs with large amounts of beta-carotene and vitamin A. These might raise the risk of lung cancer. Too much vitamin A during pregnancy can raise the chance of birth defects.

If you take a blood thinner like warfarin, talk to your health care provider before taking any MVM with vitamin K. It can make the medicine work less well.

How to choose

Ask your provider if you need one and which kind. You can pick an MVM made for your age and sex. ODS says products for adults over 50 usually have more calcium, vitamin D and B12 and less iron than ones for younger adults. Check the %DV, or Daily Value, on the label. It shows how much of a nutrient one serving gives you.

The bottom line

Build your plate first. Eat a variety of foods. If you think you have a gap, talk with your doctor, a dietitian or a pharmacist before you buy anything.