A new study provides encouraging evidence.
Want to eat a healthier diet and help save the planet? Try becoming a vegetarian. You’ll avoid supporting a livestock industry that emits vast amounts of greenhouse gases.
You’ll reduce your risk of heart disease and diabetes with the foods you eat.
Plant-based diets are also associated with a lower risk of certain types of cancer. But what about prostate cancer in particular?
Earlier this year, researchers published the results of a comprehensive literature review on plant-based diets and prostate cancer risk. They concluded that in addition to benefits for cardiovascular health and quality of life, plant-based diets might improve prostate cancer outcomes.
Plants contain several anti-cancer compounds, such as flavonoids, tannins, and resveratrol. On the other hand, cooking meat (especially red meat and processed meat) generates two carcinogens: heterocyclic amines, which appear during pan-frying, and polycyclic aromatic hydrocarbons, which are produced during grilling or barbecuing.
The researchers responsible for the new review analyzed 32 studies evaluating possible links between plant-based diets and a reduced risk of prostate cancer. One-third of the studies were observational, meaning the research was based on pre-existing information in databases and health registries. The remaining studies were interventional; the subjects included were prostate cancer patients who were followed over time to see if changes in diet, exercise, stress management, and other lifestyle interventions resulted in better outcomes.
Overall, the studies favored the beneficial effects of eating plant-based foods. Most observational studies showed that plant food eaters developed prostate cancer at a lower rate than meat eaters. And 60% of intervention studies indicated that prostate-specific antigen (PSA) levels increased more slowly in plant food eaters than in meat eaters. An increase in PSA suggests that prostate cancer is worsening or recurring in men who have already been treated for the disease.
Comments and background
The review authors pointed to evidence of PSA, better overall health status, and a later need for additional prostate cancer treatment in vegetable eaters to support the conclusion that vegetarian diets are protective. However, large-scale clinical trials are still needed to confirm this association, cautioned Stephen Freedland, MD, urologist, and director of the Center for Integrated Cancer and Lifestyle Research at Cedars-Sinai Medical Center in Los Angeles.
In a follow-up editorial, last October, Dr. Freedland and his coauthors pointed out gaps in the existing data. For example, the intervention studies cited in the recent review article are small (fewer than 100 subjects each), with follow-ups of no more than one year, and the observational data are far from unanimous, with some studies detecting no association between prostate cancer risk and vegetarian diets, while others showed conflicting results.
Another issue is the need for greater consensus on what constitutes a plant-based diet. Definitions can range from extreme vegan to semi-vegetarian to predominantly plant-based, where some meat consumption is allowed. One of the interventions cited in the review was described as “an increase in plant-based and oily fish diets and a reduction or elimination of protein from land animals.”
“What we need in this field are more rigorous, well-controlled randomized clinical trials,” Dr. Freedland says. “We need to determine whether the diet is protective or whether vegetarians and vegans are more health conscious in other ways. Do they exercise more? Do they have better access to health care? Do they live in places with better air quality? These are the questions we need to answer.”
Despite these limitations, Dr. Freedland called the evidence linking vegetarianism to a lower risk of prostate cancer intriguing and encouraging. Meanwhile, he advises that the best lifestyle strategy for reducing overall cancer risk is to avoid obesity. “That’s where we have the best evidence,” he says.
