Diets to fight prostate cancer may hinge on beating obesity
As many as 3 out of 4 men with prostate cancer, according to Dean Ornish’s research and the current, July issue of Harvard Men’s Health Watch newsletter, take nonprescription supplements. Some of these men use diet, exercise, or both in the hope of improving their outcome. While most of them also receive conventional therapy, a minority relies on lifestyle changes during “active surveillance” before active primary therapy or after biochemical recurrence (rising PSA) following surgery or radiotherapy.
Do lifestyle changes actually work? “Experts don’t know,” the Harvard folks say, “though research raises hope that it may have a beneficial impact.”
Dean Ornish, who pioneered lifestyle change for heart patients, conducted a clinical study of similar changes for men with prostate cancer and reported results in 2005 (Intensive lifestyle changes may affect the progression of prostate cancer.) Harvard Health writes:
All of the 93 men who signed up for the trial had newly diagnosed low- to moderate-grade cancers that were localized to the prostate gland. Half were randomly assigned to a lifestyle program, and half got no advice on lifestyle changes. The program that researchers created included four elements: An ultra-low-fat vegan diet; supplements, including soy, fish oil, vitamins E and C, and selenium; an exercise program of walking 30 minutes six days a week; and stress reduction that included yoga-based stretching, breathing, and meditation for an hour a day.
At the end of a year, a small but significant difference was evident. The average PSA in the intensive lifestyle group fell, whereas the average PSA in the untreated men rose. The participants in the lifestyle group also showed favorable cancer-fighting changes in their blood.
Much more research is needed before lifestyle therapy can be recommended clinically. But, the Harvard Men’s Health Watch notes, men with prostate cancer may choose not to wait until science catches up with their disease. And since the lifestyle program studied is good for general health, its elements will make a reasonable addition to any prostate cancer program.
The results which Harvard Health is touting this month first appeared in print two years ago. Ornish updated them in a 2006 spin-off from the same study, which finds that men in the active surveillance arm who made lifestyle changes toward low-fat, vegan diet, exercise, and stress management improved their mental and physical health-related quality of life and sexual function.
Dr. Ornish emphasized a vegan diet high in soy proteins on the hypothesis that this would slow down prostate cancer prgression by reducing insulin-like growth factor levels and increasing levels of insulin-like growth factor binding proteins. He writes:
High levels of insulin-like growth factor 1 (IGF-1) are associated with increased risk of prostate cancer, whereas increased levels of some of its binding proteins (IGFBPs) seem to be protective. High intakes of dietary protein, especially animal and soy protein, appear to increase IGF-1. However, soy isoflavones have demonstrated anti-proliferative and apoptotic effects both in vitro and in vivo. We evaluated dietary intakes of total protein and soy isoflavones in relation to the IGF axis in prostate cancer patients making comprehensive lifestyle changes including a very low-fat vegan diet supplemented with soy protein (58 g/day). After one year, intervention group patients reported significantly higher intakes of dietary protein and soy isoflavones compared to usual-care controls (P < 0.001). IGF-1 increased significantly in both groups, whereas IGFBP-1 rose in the experimental group only (P < 0.01). Increases in vegetable protein over one year were associated with increases in IGFBP-1 among intervention group patients (P < 0.05). These results suggest that dietary protein and soy isoflavones, in the context of comprehensive lifestyle changes, may not significantly alter IGF-1. However, given the recent literature indicating that high intake of protein rich in essential amino acids (animal or soy protein) may increase IGF-1, it may be prudent for men with early stage prostate cancer not to exceed dietary protein recommendations.
Meanwhile another researcher, David Feldman at Stanford, has reported that 1) high dose vitamin D (calcitriol) has antiproliferative actions on LNCaP (metastatic, androgen-dependent) human prostate cancer cells ; 2) this action is “mediated mainly by induction of insulin-like growth factor binding protein 3 (IGFBP-3); 3) “androgens increase expression of IGFBP-3 and cause a major enhancement of IGFBP-3 stimulation by calcitriol.”
Further, Japanese researchers have found that insulin-like growth factor binding protein 6 boosts the action of artificial estrogen (DES) on both androgen-sensitive and androgen insensitive prostate cancer cells.
Arab men have low levels of prostate cancer. A recent study found that “As in Caucasians, serum IGF-1 and IGFBP-3 levels declined with age in Arab men” and that “Arab men with newly diagnosed prostate cancer had significantly higher serum IGF-1 level (P<0.01) and lower IGFBP-3 levels (P<0.01) compared to age-matched Arabs without the disease.”
Would it make sense just to take supplements or some kind of drug to bring about a better IGF-1 to IGFBP ratio or are lifestyle changes necessary or at least preferable (as Ornish believes)? Last month (Int J Cancer. 2007 Jun 27) the Cancer Epidemiology and Genetics division at NCI/NIH reported that in their large population based study, no clear linkage between prostate cancer risk and IGF-1 and IGFBP-3 levels and ratios leaped out except in obese men:
There was no clear overall association between IGF-1, IGFBP-3 and IGF-1:IGFBP-3 molar ratio (IGFmr) and prostate cancer risk, however, IGFmr was associated with risk in obese men (BMI > 30, p-trend = 0.04), with a greater than 2-fold increased risk in the highest IGFmr quartile….
So, while the laboratory studies of cancer cells and tumors implanted in mice may lead to new pharmaceuticals down the line, for men today a reasonable goal is a leaner body achieved through a combination of diet, stress reduction, and exercise. Dean Ornish has mapped out one path to this goal, other paths are available and may be just as effective.
