Eating lots of vegetables every day is one of the most powerful things anyone can do to prevent a wide variety of diseases, including cancer. Researchers have been puzzled, though, why the protective effect for breast cancer has not been as strong or consistent as for some of the other cancers. Researchers in Germany may have just found a clue to the mystery.[2]
The researchers looked at the past diets of hundreds of breast cancer victims and healthy controls, and like many studies before them, they found a modest trend towards decreased risk of breast cancer development in people with the highest daily vegetable consumption. But when they broke up intake categories into raw vegetables versus cooked vegetables, they were surprised to find that women who ate just a single small salad a day seemed to cut their risk of developing breast cancer in half (compared to those who like only ate a salad every couple days) while the women eating the most cooked veggies didn't seem to have any protection from developing breast cancer at all.
Cooking reduces the availability of some of the carotenoids in vegetables like lutein, zeaxanthin, and B-cryptoxanthin, but cooking also actually increases the bioavailability of other carotenoids like lycopene, alpha carotene and beta carotene. So I encourage people to eat a variety of cooked and raw foods. Although this study did show that raw vegetables seemed to have a distinct advantage, for example, it also showed that women who ate cooked whole grain products like whole wheat bread and brown rice also seemed significantly protected from developing breast cancer.
The mechanism by which vegetables decrease cancer risk is unknown, but evidence suggests that it's immune related. Our immune system has special cells called natural killer cells, whose mission in life is to just go around killing cancer cells. Their job is to rove around the body on seek and destroy missions trying to remove any budding tumors anywhere in our body. Our mission (if we choose to accept it) is to boost their cancer-fighting abilities. That's where vegetables come in. A recent study, for example, found that those drinking vegetable juice (carrot or tomato) every day significantly increased the cancer fighting ability of their immune system.[3]
It's time for all of us to get back to our salad days of youth.
Michael Greger, M.D. is a general practitioner specializing in vegetarian nutrition, a prize-winning cook, and an internationally recognized speaker on a number of important public health and social justice issues. He is author of Heart Failure: Diary of a Third Year Medical Student and has contributed to a number of books on veganism and food safety issues. All proceeds from the sale of his books, CDs, and DVDs is all distributed to vegan charities. For more information about Dr. Greger, please visit his website Vegan MD.
