Prostate cancer is the second most common cancer in men, following nonmelanoma skin cancer. Prostate cancer is also the second leading cause of death from cancer in men, just behind lung cancer. About one in 10 men will be diagnosed with prostate cancer, with most cases occurring in men over 65.
In fact, many researchers think that all men develop prostate cancer if they live long enough, although most types are confined to the prostate gland and are not the cause of death. As with all cancers, finding prostate cancer early leads to a far greater chance of survival. Once it has spread to other areas, such as the bones, the five-year survival rate drops to about 50 percent.
The big debate about prostate cancer is how it’s affected by diet. Most studies show that eating a higher-fat diet, especially saturated fat, increases the incidence of prostate cancer. Genetics and hormones also play a role. If you had a close male relative who had prostate cancer, your chance of developing it increases. Prostatic tissue growth is also known to be stimulated by testosterone. Black American males have a 40 percent higher rate of prostate cancer than white males, which is thought to be due to the higher average testosterone level in black men than in white men.
The point of contention among researchers who study the incidence of prostate cancer is whether dietary saturated fat is the culprit or if it’s a case of excess calories due to increased fat intake. At nine per gram, fat contains the greatest amount of calories, compared to four per gram for protein and carbohydrates. Even so, that doesn’t explain why other types of fat don’t have as great a link to prostate cancer, since they also contain nine calories per gram.
A 1998 study published in the Journal of the National Cancer Institute that surveyed prostate cancer deaths in 59 countries found that eating cereal, nuts, oil seeds and fish offered protective effects against prostate cancer, while eating red meat and dairy products caused the highest mortality levels. The authors speculated that animal fats were especially potent promoters of prostate cancer because they also increase testosterone production, which in turn promotes prostate cancer.
Another study, this one published in 1998 in the Journal of Urology, compared the diets of 142 men who had advanced prostate cancer (cancer that has spread to other body tissues) to those of 242 men who had localized prostate cancer. The researchers found that men with advanced cancer consumed more saturated and animal fats and had a lower intake of polyunsaturated and vegetable oils.
What is it about saturated fat that may promote prostate cancer? It can’t be just the increased energy factor, since all fats contain the same caloric density. One study that looked at the molecular mechanisms behind prostate cancer found that a particular fatty acid commonly occurring in animal fat, arachidonic acid, stimulates proliferation of prostate cancer cells and that blocking its activity led to a rapid death of prostate cancer cells.1
A recent study of 2,270 Arab men found that even though they ate more than 120 grams of fat derived from meat and dairy products (comprising more than 40 percent of total daily calories), they showed unusually low incidences of prostate cancer. Something in the men’s diets appears to protect them from the disease.2
Dietary factors that have been shown to protect men against prostate cancer include high fiber intake; lycopene, which is found in cooked tomatoes; green tea; fruits; vegetables, especially cruciferous vegetables, such as broccoli; and omega-3 fatty acids, which are found in fatty fish like mackerel, halibut and sardines. Omega-3 fats oppose the activity of arachidonic acid and thus may protect at the cellular level. Other protective nutrients include vitamins E and D and soy foods (by blocking the effects of testosterone).
Since a lifetime of testosterone production may predispose men to getting prostate cancer, it would be prudent for all men to ensure that they take in those protective factors. That may be particularly important if they routinely eat more fat.
1 Ghosh, J., et al. (1998). Inhibition of arachidonate 5-lipooxygenase triggers massive apoptosis in human prostate cancer cells. Proc Natl Acad Sci USA. 27:1382-7.
2 Hanash, K.A., et al. (2000). Prostatic carcinoma: a nutritional disease? Conflicting data from the Kingdom of Saudi Arabia. J Urology. 164:1570-72.