Multivitamins: Helpful Or Harmful

LEXINGTON, Ky. (Nov. 16 2011) - The following column appeared this week in the Lexington Herald-Leader.

Multivitamins:  Helpful or Harmful?

By Karina Christopher

Multivitamins can be a useful tool for those who have dietary imbalances or different nutritional needs. A vitamin deficiency on its own can lead to serious problems -- for example, low iron can cause fatigue, a lack of vitamin E can lead to neurological problems, and a calcium deficiency can cause osteoporosis.

Many of my cancer patients wonder if a multivitamin will help them before, during and after cancer treatment. Research studies are currently being conducted to look at multivitamins and individual vitamins and minerals to help prevent cancer and for reducing tumor growth. However, little evidence exists right now to support the prevention of cancer through multivitamins.

As a matter of fact, in some studies, research has found that taking large doses of certain vitamins may even increase the chance of some cancers. So how do you decide when to supplement your diet with a multivitamin? The following may help.

When do I need to take a multivitamin?

Most experts agree that individuals who are unable to eat a variety of fruits and vegetables, either because of illness or finances, should take a standard multivitamin. During cancer treatment, many patients will experience more than 10 pounds of weight loss or are unable to eat for more than a week.  In circumstances such as these, a multivitamin may be necessary. Always ask your physician before starting any vitamin or mineral supplements. In many cases, blood work will determine if a deficiency exists.

What type of multivitamin is best?

A standard multivitamin is recommended for most people.  Multivitamins that have more than 100 percent the Dietary Reference Intakes (DRI) put people at risk for vitamin toxicities.  Also, if you take a standard multivitamin along with a separate vitamin or mineral supplement, you may be putting yourself at risk for developing a vitamin or mineral toxicity.

What is the best way to get enough vitamins and minerals in my diet?

At this time, it is unclear how much of the multivitamin an individual actually absorbs from a pill. Thus, multivitamins can be helpful, but research suggests that eating a variety of fruits and vegetables is the best way to get the vitamins and minerals you need. The combination of vitamins, minerals and phytochemicals in fruits and vegetables provides a greater benefit for cancer prevention than taking a pill. Aim for 5-9 servings of fruits and vegetables daily, and make your plate diverse and colorful, to help to reduce your risk of developing cancer. 

Do any supplements cause cancer?

Taking excess amounts of some supplements will actually increase the risk of developing cancer. For example, studies have shown that excess beta carotene can increase risk lung cancer risk in smokers. Research has also suggested vitamin E supplementation in amounts of 400 international units or higher may increase the risk of prostate cancer.

Karina Christopher is a registered dietitian at the UK Markey Cancer Center and runs the Markey Menu blog at ukhealthcare.uky.edu/MarkeyMenu.