This post is prompted by a new Italian meta-analysis [1] of:
"a total of nine" "eligible studies {that} compared vegetarian, semi- and pesco-vegetarian diets with a non-vegetarian diet."
"Studies were conducted on six cohorts accounting for 686,629 individuals, and ... 1,935 cases of ... prostate cancer"
"None of the analyses showed a significant association of vegetarian diet and a lower risk of ... prostate cancer compared to a non-vegetarian diet."
(This study did not address the more pressing issue of diet & survival.)
[2] (1985 - U.S. - Seventh-Day Adventists)
This small early study reported that:
"Plasma levels of testosterone and estradiol-17 beta were significantly lower in the {vegetarians} than in the omnivores."
"Implications include the possible modification of prostate cancer risk through dietary intervention."
The authors seem to feel that (a) vegetarianism just has to be beneficial & that (b) lower testosterone [T] must protect against PCa. In fact, in matched control studies, PCa cases have lower T on average. Any benefit of a vegetarian diet might be somewhat offset by lower T. (Age itself, which is a PCa risk factor, lowers T by 1-2% per year from the early 30's.)
[3] (1999 - U.K. meta-analysis of 5 studies)
"The absence of a significant association of vegetarianism with prostate cancer mortality in the current analysis does not support the hypothesis that meat may increase the risk for this cancer"
[4] (2016 - Italy - different team than [1])
"Aim of this study was to clarify the association between vegetarian, vegan diets, risk factors for chronic diseases, risk of all-cause mortality, incidence and mortality from cardio-cerebrovascular diseases, total cancer and specific type of cancer (colorectal, breast, prostate and lung), through meta-analysis."
"Eighty-six cross-sectional and 10 cohort prospective studies were included. The overall analysis among cross-sectional studies reported significant reduced levels of body mass index, total cholesterol, LDL-cholesterol, and glucose levels in vegetarians and vegans versus omnivores. With regard to prospective cohort studies, the analysis showed a significant reduced risk of incidence and/or mortality from ischemic heart disease (RR 0.75 ...) and incidence of total cancer (RR 0.92 ...) but not of total cardiovascular and cerebrovascular diseases, all-cause mortality and mortality from cancer."
The Abstract doesn't state how PCa incidence is affected. Interesting that there was no reduction in "all-cause mortality". & apparently, no reduction in PCa mortality.
I lost over a 100 lbs, and I need another 28 lbs off. I didn't eat red meat for five years, no beef, lamb or pork. Now, I think red meat in moderation is good, once or twice a week. Eating is one of the rare pleasures we have left to enjoy life.
A good research that makes me feel better in my choices. Thank you, Patrick
Did these studies make a clear cut distinction between vegetarians and vegans?
As you know vegans unlike vegetarians do NOT partake of DAIRY,EGGS or FISH,each of which has been implicated in cancer causation. Note: correlation is not necessarily causation but animal studies & tissue culture studies have also brought some concerns about these 3 food classes.
I would say that most studies seem to lump vegans in with vegetarians.
With respect to vegans, it might be useful to have separate numbers for Ornish-vegans who aim for 10% fat. Or even those on a raw vegan diet.
My interest in diet when posting to this group, is PCa mortality-survival. In a general study of "Cancer in British vegetarians" [1]:
"When vegans were examined as a separate group for the 3 commonest cancers, with meat eaters as the reference group, there were no significant associations with risk of colorectal, breast, or prostate cancer, but vegans had a 19% lower risk than did meat eaters for all cancers combined ..."
Which suggests that veganism has cancer-related merits - but not as protection against PCa.
One area of risk that can touch on mortality, is the risk of fracture. In study [2]:
"Compared with meat eaters, fracture incidence rate ratios in men and women combined adjusted for sex, age and non-dietary factors were 1.01 ... for fish eaters, 1.00 ... for vegetarians and 1.30 ... for vegans.".
Put another way, vegans had 30% increased risk of fracture when compared to vegetarians.
W/O getting into a debate on benefits of veganism ( vs vegetarianism vs omnivorisn),just as there are low information voters there are low information vegans that can get themselves in serious trouble.
2 crucial vitamins essentially absent from a vegan diet are Vit D & B12. We know both of these are vital to bone health. W/O supplements vegans have been known to get bad neurological problems (B12) and certainly we know what a large % of even omnivores are vitamin D deficient. Even the current minimum daily requirement for vit D is suspected of being grossly inadequate and the "toxic" level is being questioned as hype.
It takes a lot of study to be a safe vegan and was surprising to me when I had a dietary consult at my local cancer center how little the staff dietitian knew. It would be interesting if somebody did a longitudinal study on vegan bone health controlled for things such as vit D levels at upper normal B12,adequate plant-source calcium,etc.
& note that the vitamin K2 that comes from dairy is protective against PCa. It also has a much longer half-life than the K1 from greens, & that might have an effect on calcium transport to bones.
& then there are the marine omega-3 fatty acids: EPA & DHA.
I wouldn't read too much into vegan studies because too many get into it knowing what to cut out, without being aware of the micro-nutrients that are being lost. Some of the vegan sites don't help when they insist that supplements aren't necessary.
The issue of supplements is thorny - e.g. cholecalciferol (vitamin D) is from animal sources.
As in all things too much of anything has short term satisfaction but potential long term affects. Ive gone back and forth on the food issue. I think moderation of meats, more fish and fresh vegetables is a good variety. I just don't believe there is one way of eating that will cure cancer in everybody. Some people are wired for that, others not. Eating healthier can't hurt; perhaps trying to find the "holy grail" of diet is more stressful than necessary. We should find as much enjoyment in as many things as possible. Denial at this stage of the game just doesn't seem appropriate. Just my opinion, this is not to say what others do is inappropriate or wrong. Be blessed everyone!
I don't think any of us on this forum believe.supplements(curcumin,flax seed,etc) or diets or even the prescription meds (metformin,statins,avodart etc) will "cure cancer"
Each of these things individually MAY have a tiny marginal,perhaps not even statistically significant effect in giant studies w/r overall survival. Many of us though,I think, try or are prescribed a number of these on the theory that as long as it doesn't hurt us the CUMULATIVE marginal benefits may add up to significance
Things like a vegan diet,metformin statins are directed much more toward combatting diabetes,heart disease and stroke (which may kill more of us than the PCa) due to the adverse effects of various ADT therapies
"Denial at this stage of the game just doesn't seem appropriate"-what stage of the game are you referring? you're absolutely right if you are at the hospice stage. But if you have a prognosis of several years,why not do what might help you avert diabetes,heart disease stroke during those years ?
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Study shows supplement successfully fights lethal prostate cancer
Mortality Probability after first PSA rise vs non-castrate testosterone levels (low vs Normal)
Statin Use May Reduce Mortality in High-Risk Prostate Cancer 
Calcium supplement with vitamin D
