Can Antioxidants Prevent Cancer?
May 03 2009
You will find a lot of people taking multivitamin, Vit C, Beta carotene, & Vit E to prevent cancer.But the recent cancer prevention studies paints an entirely different story.
Why use antioxidants to prevent cancer?
Prevent Oxidative Stress: Antioxidants can neutralize free radicals or oxidative stress which may cause damage to cells and cell processes , and thereby increase the risk of cancer.
Studies: A large number of epidemiological studies have shown that a diet high in fruits, vegetables, and plants can lower risk of cancer. This same was shown in animals studies and cell culture studies that antioxidants can prevent or delay the development of cancer.
What are the major antioxidants used to prevent cancer?
The major antioxidants used in studies to prevent cancer are: Vitamin E, Vitamin C, Beta carotene, & Selenium.
And did antioxidants prevent cancer?
The results of the studies- spanning three decades of research - have been extremely disappointing to say the least. A few of the recent large trials showed no benefit of antioxidants for cancer prevention.
Other Nutrients: Even other vitamins like folic acid, Vit b6, B12, Calcium, Vitamin D which showed tremendous hope have failed to deliver.
SELECT Study: The biggest blow to cancer prevention was the recently concluded SELECT study (Selenium and Vitamin E Cancer Prevention Trial), which is the largest cancer prevention study . Though very promising, the study failed to show any beneficial effect of selenium and Vitamin E for reducing the risk of prostrate cancers and was terminated early.
Can antioxidants increase the risk of cancer?
Surprisingly, a couple of studies of large studies have shown that antioxidants may increase the risk of cancers.
Increase in Lung Cancer: The CARET study (Beta-Carotene and Retinol Efficacy Trial) showed that beta carotene supplements in smokers increase the risk of lung cancer. The similar results from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study and the high incidence of lung cancer in the participants prompted the researchers to stop the study early.
Increase in Prostrate Cancer: In a recent study (secondary findings), the author concluded that daily supplementation with 1 mg of folic acid was associated with an increased risk of prostate cancer.
Why antioxidant studies failed to prevent cancer?
There has been a lot of explanations. Below are the major ones:
- The epidemiological studies that showed benefits had whole foods, which usually is a complex mix of several nutrients. The antioxidant studies used specific single nutrient isolated from food.
- The effects of specific nutrients depend on the genetic make up of the individual.
- A deficiency of certain antioxidants or nutrient might increase cancer risk. Also an excess of the same nutrient may increase cancer risk. A good example is folate.
- Oxidative stress & free radicals are not evil. They have a beneficial effect too.
Conclusion
- The best way to get antioxidants and maybe prevent cancer is eat a lot of fruits & vegetables. The American Cancer Society recommends eating at least 5 servings of these foods every day.
- We don’t have too much evidence to advocate high doses of single antioxidant to prevent cancer. In some cases, excess may increase the risk of cancer.
