Meat consumption has been linked to an increased risk of prostate cancer in several reports. This association is related to the introduction of excess hormones and the presence of insulin-like growth factor-1 (IGF-1), which can promote the growth and spread of cancer cells. A plant-based diet can help lower IGF-1 and thereby reduce the risk of prostate cancer, but how “plant-based” should your diet be?
Plant-based diets and prostate cancer risk
The key is the relationship between prostate cancer risk and IGF-1 levels. IGF-1 is a protein that aids growth in childhood and plays a role during adulthood. A study led by Dr. Dean Ornish assigned 93 men with early prostate cancer either a comprehensive program that included a plant-based diet, exercise, and meditation, or a conventional diet and usual care. Those who followed the plant-based diet had a 4% decline in prostate-specific antigen (PSA) levels, compared to a 6% increase in the control group. Additionally, the prostate cancer cell growth was inhibited nearly eightfold in the comprehensive care group.
Research also shows that men and women who consume a vegan diet have significantly lower IGF-1 levels, which translates into a lower risk of aggressive hormone-dependent prostate cancer. A study found that individuals who follow a plant-based diet for 14 years have half the IGF-1 levels and more than twice the amount of IGF-binding protein than those who consume a Standard American Diet. Lower levels of IGF-1 in vegan dieters were also linked to a reduced risk of another hormone-associated cancer, breast cancer.
Vegan vs. vegetarian diets
The question remains: is a vegan diet necessary instead of a vegetarian one to reduce prostate and breast cancer risk? Some studies indicate it does make a difference. A British study compared IGF-1 levels in vegan, vegetarian (ovo-lacto, consuming eggs and dairy), and meat-eater men, finding a 9% lower IGF-1 level in vegans. This result was associated with the vegans’ ability to bind up considerably more excess IGF-1 in their bloodstream. Vegan men also had higher testosterone levels than the other two groups, but this was offset by higher levels of sex hormone binding globulin (SHBG), which bonds with and transports testosterone throughout the body.
As a result, research suggests that men and women can benefit from following a plant-based diet in terms of reducing levels of the cancer-promoter IGF-1. However, to achieve a significant decline in these levels, it seems a vegan dietary plan is the most effective choice.
