Soy and tomato combo may be effective in preventing prostate cancer

Tomatoes and soy foods may be more effective in preventing prostate cancer when they are eaten together than when either is eaten alone, said a University of Illinois study.

“In our study, we used mice that were genetically engineered to develop an aggressive form of prostate cancer. Even so, half the animals that had consumed tomato and soy had no cancerous lesions in the prostate at study’s end. All the mice in the control group - no soy, no tomato - developed the disease,” said John Erdman, a U of I professor of food science and nutrition.

From the time they were 4 to 18 weeks old, the animals were fed one of four diets: (1) 10 percent whole tomato powder; (2) 2 percent soy germ; (3) tomato powder plus soy germ; and (4) a control group that ate neither tomato nor soy.

The 4- to 18-week time frame modeled an early and lifelong exposure to the bioactive components in these foods, he said.

“Eating tomato, soy, and the combination all significantly reduced prostate cancer incidence. But the combination gave us the best results. Only 45 percent of mice fed both foods developed the disease compared to 61 percent in the tomato group, and 66 percent in the soy group,” he said.

Prostate cancer is the most frequently diagnosed cancer in men, but the disease has nearly a 100 percent survival rate if it’s caught early. In older men, it is often a slow-growing cancer, and these men often choose watchful waiting over radiation and surgical treatments that have unwelcome side effects, said Krystle Zuniga, co-author of the paper.

Prostate cancer is the most common cancer for men in Western countries. A man’s risk of developing prostate cancer is 35% higher than a woman’s risk of getting breast cancer. In 2009, an estimated 192,000 men in America will be diagnosed with prostate cancer, and an estimated 27,000 people will die from this relatively slow-growing cancer this year. If current trends continue, 1 in 6 American men will develop prostate cancer during his lifetime.

preventing PRostate Cancer

Under normal conditions, cells within the prostate grow, divide, and die in a controlled manner. Prostate cancer develops when the cells begin to grow out of control. Instead of dying, these cells outlive normal cells, invade adjacent tissues, and sometimes spread to other parts of the body (process called metastasis). Abnormal cell growths are called tumors. Prostate cancer is usually comprised of several very small tumors within the prostate. Provided it has not metastasized to other parts of the body, prostate cancer can often be successfully treated with surgery or radiation. Unfortunately, as it usually causes no symptoms early on, prostate cancer is often diagnosed only at a later stage when it has already spread to other parts of the body.

People with a family history of prostate cancer have a significantly higher risk of developing the disease than men without close relatives diagnosed with the disease. Men with a single first-degree relative (father, brother or son) with a history of prostate cancer are twice as likely to be diagnosed with the disease, while those with at least two close relatives affected are nearly four times as likely to develop the disease. The risk increases further if the family members were affected at a young age. Although genetics seem to influence a man’s risk of developing prostate cancer, lifestyle factors, such as diet, are likely to have an effect as well.

Soy isoflavone serum and prostate levels in the mice are similar to those found in Asian men who consume one to two servings of soy daily. In countries where soy is eaten regularly, prostate cancer occurs at significantly lower levels, Erdman noted.

Avoid Excess Protein

More than hundred years ago John Beard, a Scottish doctor, discovered that the body’s primary defense against proliferating cancer cells is pancreatin, a mix of enzymes that are also involved in the digestion of proteins. High protein diets force pancreatic enzymes to focus on the digestion of protein rather than on the eradication of cancer. A certain amount of protein is necessary for the proper functioning of the body, but excessive amounts of protein should be avoided if you want to reduce your odds of developing prostate cancer. It may be a good idea to skip protein at one or two meals a day. Indeed, some experts believe that the body needs a protein-free period of approximately 12 hours a day in order to combat cancer.

Count on Curcumin

Curcumin, a plant pigment responsible for turmeric’s bright yellow color, has been used in Ayurvedic and Chinese medicine for centuries due to its beneficial effects on a wide range of diseases and conditions. In recent years, also western medicine has started to pay greater attention to this extraordinary compound. Recent studies suggest that curcumin could be effective not only at preventing prostate cancer but also at inhibiting the spread of existing prostate cancers. Curcumin has been shown to be able to trigger apoptosis (programmed cell death) in human cancer cells and to scavenge free radicals. It may also help prevent nitrosamine formation and aflatoxin production which have been associated with an increased risk of cancer.

Avoid Meat Products That Contain Nitrates

Nitrates are substances that naturally occur in our environment. They can be found in the air, soil, surface water, ground water, and plants. They are also used in processed and cured meat products to give meat a nice red color. The body can convert nitrates present in food into nitrites, which in turn can form nitrosamines. Evidence has directly linked nitrosamine exposure to cancer in humans. Luckily, nitrosamine formation is inhibited by certain antioxidants, including vitamin C and vitamin E, and therefore nitrosamine formation is usually not a concern if you eat plenty of vegetables (which are typically rich in antioxidants). This is supported by population studies which have foudn no association between a high consumption of nitrate-containing vegetables and cancer, but which show that diets rich in nitrate-containing processed meats are a risk factor.

Eat Plenty of Foods Rich in Vitamin A and Carotenoids

A large and compelling body of evidence indicates that a diet rich in foods that contain vitamin A and its precursors, carotenoids, can help reduce the risk of many types of cancer. Carotenoids are pigments that give many fruits and vegetables such as cantaloupe, sweet potato, carrots, kale, spinach, and collard greens their vibrant colors. The most common carotenoids in the Western diet are beta-carotene, lycopene, lutein and zeaxanthin. Foods rich in vitamin A and carotenoids have been shown to be particularly effective at preventing lung cancer, but also the risk of prostate cancer may be significantly reduced by eating plenty of these foods.

How much soy and tomato should a 55-year-old man concerned about prostate health eat in order to receive these benefits?

“The results of the mouse study suggest that three to four servings of tomato products per week and one to two servings of soy foods daily could protect against prostate cancer,” Zuniga said.

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