I am always on the hunt for prostate cancer cures and methods of prevention. I consider it to be just as interesting a topic as testosterone itself. The reason is simple: if my PSA rises, then it's game over: I may have to go off of HRT. (Morgentaler's study calls this into question, but I am giving here the prevailing medical sentiment.) Plus, it may be game over as in permanently! I knew someone who had metastatic prostate cancer and this very nice guy was here one day and almost literally gone the next.
As you'll see below, there is a new way that will likely significantly reduce your PSA and provide substantial prostate cancer as well. And I have seen very little coverage on the subject and feel that this deserves mention to say the least. This is especially true since prostate cancer is incredibly common, especially in Western societies. As I discuss elsewhere on the site, HCA's from cooked red meat were a huge part of my early diet and experts feel these are likely culprits in prostate cancer development. One prospective study found that there was a 20% risk increase of prostate cancer (and even greater risk of other diseases) from certain HCA's and concluded:
"Very well done meat was positively associated with prostate cancer risk. In addition, this study lends epidemiologic support to the animal studies, which have implicated PhIP as a prostate carcinogen." 
And one study showed that about 1 in 6 men with a PSA < 4.0 developed prostate cancer in seven years.  In other words, this is a very common cancer and, in fact, is only exceeded by lung cancer and heart disease as a killer of men. 
NOTE: It should be noted that one of the leading researchers believes that testosterone has nothing to do with prostate cancer and has built a strong case to support that assertion. He tells his side of the argument here in this must-read article. In addition, it should be pointed out that the PSA exam is far from perfect and can fluctuate considerably due to exercise, sexual activity, infections and so on. That said, PSA is certainly not always wrong.
So is there any way for someone like myself, who ate a ton of fast food hamburger cooked at near blast furnace temperatures to put the odds back in his favor? Yes, that appears to be the case and researchers have been lasering in on flaxseed for the last decade, because it seems to have anti-prostate cancer superpowers. Let's look at the interesting history of flax seeds on this subject:
1. Pre-2001. Interestingly enough, prior to about 2005, researchers seemed to generally consider flaxseed a risk factor for prostate cancer based on several epidemiological studies. It turns out that the reasoning behind this conclusion was entirely circumstantial: it was actually ALA (alpha-linolenic acid, NOT alpha lipoic acid) in the diet that was linked in these studies to prostate cancer.  Experts assumed that since flaxseed was high in ALA that this meant it was linked to prostate cancer risk.
My guess is that there is a logical explanation for the above: one of the big sources of ALA in the diet are some of the standard cooking oils such as safflower, sunflower, canola, etc. These oils, being high in omega-6's, can increase inflammation if over consumed and animal studies show they accelerate prostate cancer.
2. 2001 Study of Low Fat + Flaxseed. The concern about flaxseed really turned around in 2001 with a study lead by Wendy Demark-Wahnefried that looked at men with actual prostate cancer. These men were put on a low fat diet - less than 20% fat by their definition - and 30 grams of flax seed per day. The way they conducted the study was particularly impressive, because all the particpants were waiting for a prostatectomy, i.e. the researchers were able to examine the prostate tissue of the men and examine the actual spread of the prostate cancer.
What they found was the removed prostates of the men on the Low Fat Diet with flaxseed and "matched by age, race, prostate-specific antigen level at diagnosis, and biopsy Gleason sum" had a much greater rate of cancer cell death and a much lower rate of cancer cell proliferation. Furthermore, those with lower a Gleason score less than 6.0 had lower PSA's.  Suddenly, it dawned on everyone that not all sources of alpha linolenic acid are created equal.
CAUTION: This study showed a drop in testosterone from the diet of about 15% from 420 ng/dl to 360 ng/dl. As you'll see below, this may be an anomaly as men on an identical diet experienced no change in testosterone in the study mentioned in #3 below.  In my case, it is of no concern anyway, because I am on HRT. If you are a low testosterone man, you may want to do some testosterone testing before and after just to make sure. See my link on Testosterone Labs for additional information.
3. 2004 Study of a Low Fat Diet + Flaxseed. A followup study to #2 was conducted on men scheduled for a prostate biopsy. These were men with potential prostate issue (and high PSA's). The men were put on the same kind of diet (less than 20% of total calories from fat) and 30 grams of flaxseed per day. The results were remarkable: 
4. 2008: Flax Seed More Powerful Than Low Fat Diet. A 2008 paper answered the next logical question: was it the flax seed or the Low Fat Diet that was responsible for the prostate cancer protection? All of the above studies used both simultaneously, so it is difficult to know which was the more powerful solution. To answer that questions, the same researcher (Wendy Demark-Wahnefried) at Duke University created four study groups: a) the control, b) men with flax seed, c) men on a Low Fat Diet and d) men on both flax seed and a Low Fat Diet. 
Now I am a big Low Fat Diet fan and I list the reasons here in my link on The Incredible Benefits of a Low Fat Diet. And one of those reasons is that a study by Dean Ornish indicated that a Low Fat Diet would more than likely provide substantial reductions in prostate cancer rates. However, the Ornish Study looked primarily at markers whereas this 2008 study actually examined the prostates. Like study #2, the men went on the various combinations of flaxseed and/or a Low Fat Diet for 30 days before a prostatectomy and then their prostates were examined. So this study provided the "acid test!"
The results were clear: flax seed provided the greatest protection:
Basically, it was flaxseed that provided the most prostate cancer protection, although the 20% reduction of the Low Fat Diet is pretty impressive just on its own. Remember that the classic definition of a Low Fat Diet is more around 10% of calories from fat and so this allowed double that amount. In other words, what I would call a "true" Low Fat Diet may have provided additiona protection.
However, the bottom line is that flaxseed was clearly the superstar and clearly reduced prostate cancer rates dramatically all by itself. Notice that combining it with a Low Fat Diet did not seem to provide that many synergies, only reducing prostate cancer proliferation rates by an additional 5%. However, there are other reasons to go on a Low Fat Diet as metnioned above. For additional ways, see my page on How to Lower Your Prostate Cancer Risk Naturally according to the latest research.
OMEGA-3's: One huge potential benefit of using flaxseed with a Low Fat Diet is that you may be able to reduce or eliminate your dependence on fish oil. Fish oil is an excellent source of omega-3's, but many of the world's supercultures do not consume fish yet enjoy almost perfect health with regards to the chronic diseases that plague Westerners. They get ample omega-3's through their non-fish diet, which is mostly plants and live to be 90+ in almost perfect health with no dementia or Alzheimer's.
Now why would anyone want to lower their consumption of fish oil? Well, it appears that in some cases it may increase the risk of prostate cancer according to one recent study.  And, furthermore, the problem is that more than one study has indicated this may be the case. The researchers in charge of the study actually recommended eating fish once or twice per week instead.
I hope to write a page soon on how to get (some or possibly all) of your omega-3's from flaxseed and thus reduce your dependence on fish oil. It does require a good nutritional base to do it properly as I will discuss.
DOSAGE: How much flaxseed is the 30 grams used in the above studies? I am sitting here looking at my package of ground flaxseed and it says that 2 tablespoons provide 13 grams. If you do the calculations this works out to basically 4.5 tablespoons of ground flaxseed.
For anyone following a Low Fat Diet, this would add about 10.4 grams of additional fat into your diet and would take someone from the traditional 10% fat level to 13.4% fat. If you reduce your carbs to make up for the increase in calories, it would take you up to 13.7% fat.
CAUTION: The only caution that I have about flaxseed is that I wish they would study the effect on the male brain. As I document in my link on Soy and Men, there are a couple of studies linking soy consumption to shrinkage of some brain tissues. This is a controvesial find by the way, but flaxseed also has a sizeable propopertion of phytoestrogen and so I think this would be an important study to conduct.
1) Cancer Res, Dec 15 2005, 65(24):11779-84, "A Prospective Study of Meat and Meat Mutagens and Prostate Cancer Risk"
2) N Engl J Med, 2004, 350:2239-46, "Prevalence of Prostate Cancer among Men with a Prostate-Specific Antigen Level â‰¤4.0 ng per Milliliter"
4) http://www.cspinet.org/nah/12_05/flax.pdf, "A MIRACLE SEED COMES DOWN TO EARTH", by David Schardt
5) Urology, Jul 2001, 58(1):47:52, "Pilot study of dietary fat restriction and flaxseed supplementation in men with prostate cancer before surgery: exploring the effects on hormonal levels, prostate-specific antigen, and histopathologic features"
6) Urology, May 2004, 63(5):900-904, "Pilot study to explore effects of low-fat, flaxseed-supplemented diet on proliferation of benign prostatic epithelium and prostate-specific antigen"
7) Cancer Epidemiol Biomarkers Prev, 2008 Dec, 17(12):3577â€“3587., "Flaxseed Supplementation (not Dietary Fat Restriction) Reduces Prostate Cancer Proliferation Rates in Men Presurgery"