By Peiying Yang, Ph.D., and Lorenzo Cohen, Ph.D.
In the past 50 years, the use of nutritional supplements
for the prevention of cancer has increased dramatically in the United
States. However, emerging scientific evidence strongly supports the
beneficial effects of whole foods for cancer prevention, yet little support from any single nutrient or combinations thereof.
More than 200 recent epidemiological studies indicate that whole nutritionally dense foods, especially fruits, vegetables and high-fiber foods provide more benefits than isolated nutrients in preventing various cancers.
Whole
foods contain a wide array of nutrients including vitamins, minerals
and a number of other biologically active compounds, collectively known
as phytonutrients. These phytonutrients, such as 3,3'-diindolylmethane
(DIM) in broccoli or isoprenoids and polyphenols in other vegetables,
may work in concert to provide the best support for cancer prevention
and control.
For example, fruit and vegetable combined, such as
tomato and broccoli extracts or mushroom and green tea, exhibit strong
antioxidant and antiproliferative activities in prostate cancer and potential
to reduce breast cancer risk compared to that of the individual foods alone.
Phytochemicals present in fruits and vegetables can increase the bioavailability of nutrients and together can target different molecular pathways that regulate inflammation, the immune system, and cancer cell proliferation and metastasis.
Clinical trials
In contrast to the positive impact of whole foods, a number of large cancer prevention clinical trials on nutritional supplements including vitamin E and Beta-carotene for lung cancer (ATBC and CARET trials), Vitamin E, C and Beta-carotene for prostate cancer (PLCO trial), selenium and vitamin E for prostate cancer prevention (SELECT trial), and folic acid and vitamin B for overall cancer prevention (Norweigian Vitamin Trial) did not demonstrate beneficial effect either on the reduction of cancer risk or cancer-related death.
Furthermore, higher concentrations of a single or multi-vitamin could be potentially harmful, such as vitamin A in reducing bone density and increasing hip fracture and vitamin E in hemorrhagic stroke.
Thus, the conclusion drawn from hundreds of studies is that cancer protection must come from a combination of phytonutrients in whole foods that are not in isolated supplements.
A diet that is composed of whole grains, dark green and yellow/orange vegetables and fruits, legumes, tea (green and/or black), and nuts and seeds contains high concentrations of antioxidant phenolics, fibers and phytonutrients, and would work synergistically to offer protection against many types of chronic diseases, including cancer.
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