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By Melissa Tennen, HealthAtoZ writer
If you've heard that some kind of vitamin or mineral will reduce your risk of cancer, think twice before you pop a pill. Supplements do not help reduce the risk of cancer, according to a U.S. Preventive Services Task Force report in a recent edition of the journal Annals of Internal Medicine. Explaining what this means is Melanie Polk, R.D., director of nutrition education for the American Institute for Cancer Research (AICR).
What is the issue with supplements and disease?
Melanie Polk: The issue is, are we getting enough of the substances we need to decrease our risk of cancer? We know there is a relationship between diet and cancer, and we know that diet can play a protective role. But taking these chemicals in isolation probably won't help protect you from cancer.
In 1997, AICR released a report called the Food, Nutrition and the Prevention of Cancer: a Global Perspective. That report examined more than 4,500 studies and found evidence that diets high in a variety of plant-based foods like vegetables, fruits, whole grains and beans lower risk for cancer. The report found no evidence that nutrients in supplement form can lower cancer risk.
Why do people find multivitamins so attractive?
Polk: It's easier for people to pop a pill than to change their diets. Sometimes people think they don't have time to eat healthy.
Why do people think it's okay or even better to take a pill rather than from foods?
Polk: We keep being inundated with new studies looking at individual phytochemicals. There are thousands of phytochemicals found in plant foods such as fruits and vegetables. And many phytochemicals have not been discovered.
For example, there have been studies showing the phytochemical sulforaphane, a compound in broccoli, and allyl sulfides found in leek or limonene in lemon peel may protect against cancer. Someone might read that sulforaphane fights cancer. "Well, I don't like broccoli so I'll just take a supplement."
How many people take multivitamins?
Polk: The AICR did a survey that found 43 percent of Americans said they take a daily multivitamin to reduce their risk of cancer. The belief that vitamin supplements can help prevent cancer seems particularly entrenched among seniors. In the AICR survey, 54 percent of those 65 and older said they take a multivitamin to lower their cancer risk.
If these phytochemicals and nutrients are so good for us, what's the harm?
Polk: In most cases, we don't know the harm of taking them in isolation. But we don't know the benefit either. In at least two studies with beta-carotene and smokers, we expected beta-carotene would help protect the smokers from lung cancer. But it actually did the opposite. It increased their risks. We have inadequate data to support taking large amounts of individual nutrients.
So we have to be careful. People tend to think a little is good but more is better. But there is so much information about these phytochemicals we don't know.
Consumers can be very confused when they see aisles and aisles of supplements. But you can't get the same protection from a supplement as eating a piece of fruit. We know phytochemicals work synergistically -- as a team. That means one nutrient may affect how another works in the body. They may be even more effective when working together. And there are many phytochemicals we have not discovered yet but may play a role in this team.
We really do need all these different foods to get those hundreds of protective phytochemicals.
What foods do you suggest?
Polk: Variety is really key. Eat your leafy greens such as kale and spinach and romaine. Also, your orange vegetables like carrots and the alliums such as onion, garlic and leeks. Look at a whole variety of foods. Make your salad as colorful as possible. The more vegetables you can throw in, the better. In restaurants, ask for fruit salad instead of French fries. Eat whole grains rather than refined breads and cereals.
Focus on the quality of the foods you eat. The answer to improving your health is not popping a pill. The bottom line is that the time you spend in the supplement aisle could be better spent in the produce section.
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External Source
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The American Institute for Cancer Research
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This article was reviewed and updated June 2007.
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