I kind of stumbled upon flaxseed and started putting it in my smoothies about a year ago. I did that because I had a high PSA read, which result in my HRT clinic yanking me off of HRT (TRT). That was not fun - my testosterone dropped to 111 ng/dl - and I describe the whole event in my page High PSA But No Cancer. The good news that came out of it is that I noticed that flaxseed had a couple of great studies under it's belt against prostate cancer, and so I started using it immediately. (See my page on Flaxseed and Prostate Cancer for the recent research on the subject.)
Later I found out that this was just the beginning of flaxseed's miraculous super powers: it also has considerable evidence behind it that it can stabilize and/or great slowly down the buildup of arterial plaque. And, in case you didn't appreciate the significant of that, it means that flaxseed has the potential to help you clear out penile arterial plaque. Nice!
The evidence for flaxseed in this comes mostly from animal models at this point. Rabbits provide a good model of atherosclerosis for researchers and one recent study found that a 10% flaxseed diet actually regressed plaque by 40%!  Now few of us want to eat 10% flaxseed. My three tablespoons per day is probably around 4% for example. However, I can consume flaxseed daily for years and thus likely slowly accumulate the benefits over time, something that a short term laboratory model like the above cannot do. As a side note, I love a quote from the authors of this study: "Akin to pharmaceuticals, functional foods can also be used to prevent and treat CVD [cardiovascular disease]." Hallelujah!
So is it just this one rabbit study that shows flaxseed greatly reduces the progression of arterial plaque? Well, actually there have been multiple rabbit studies. Researchers even know that the stellar results appear to be from the lignans and not the alpha linolenic acid, both of which are so abundant in flaxseed.  To prove this, they fed rabbits flaxseed with low alpha linolenic acid and it still reduced arterial plaque levels. 
Of course, the question then remains, "Will flaxseed regress plaque in humans, especially men?" Of course, we don't definitively know the answer to that yet. However, I think the answer will be 'yes,' because it manhandles virtually all the major risk factors for atherosclerosis. Flaxseed has so many anti-plaque properties that it's hard to even catalog them all, but consider these:
1. Lowering Triglyceries and LDL but not HDL. Flaxseed somehow reduces the "bad" lipids while maintaining your good cholesterol levels.  Notice that this is very similar to the effect that Niacin, which is used by some of the plaque regressers, has on lipid metabolism. Niacin, though, has the advantage of also raising HDL. However, niacin can have side effects and flaxseed has no side effects that I know of - it is a food that has been used for centuries.
One research summary stated that "multiple clinical dietary intervention trials report that consuming flaxseed daily can modestly reduce circulating total cholesterol (TC) by 6% 11% and low-density lipoprotein (LDL) cholesterol by 9% 18% in normolipemic humans and by 5% 17% for TC and 4% 10% for LDL cholesterol in hypercholesterolemic patients." 
These are powerful results and one can't help but ask the question why doctors don't hand some of their patients a bag of flaxseed instead of a prescription for statins??
2. Lowering Inflammation and CRP (C-Reactive Protein). Of course, it is no secret that flaxseed is an inflammation fighter. Other than fish itself, there is probably no more well-known source of omega-3's. Flaxseed is rich in alpha linolenic acid, which the body converts to EPA/DHA. A study on women showed that the lignans in flaxseed may also be responsible and single-handedly lowered CRP levels.  (Women convert alpha linolenic acid more readily into the EPA/DHA chain.)
3. Lowering Blood Pressure. Flaxseed contains the lignan secoisolariciresinol diglucoside (SDG), which is a powerful blood pressure lowerer.  In fact, a recent study showed that flaxseed lowered blood pressure by an average of 15 points (mm) systolic and 7 points (mm) diastolic!  This is a huge drop and rivals that of most of the phamaceutical solutions out there!
4. Lowering Blood Glucose. Yes, flaxseed was also found - the lignans again - to lower blood glucose levels in a dose dependent manner.  Yes, flaxseed does it all, battling prediabetes and diabetes on top of everything else. And the key thing to note is that both #3 (high blood pressure) and #4 (high blood sugar) are risk factor for arterial plaque.
CONCLUSION: I think that men should think of flaxseed as a protector of all they hold dear. If you stop to think about, the things that can take you out of commission in the bedroom and otherwise are plaque buildup, prostate cancer, diabetes and prediabetes, etc. All evidence points to flaxseed greatly reducing the risk for all of these, although I freely admit that more studywork needs to be done.
NOTE: See also my page on The Incredible Benefits of Flaxseed for more reasons every guy should be thinking about flaxseed.
1) Amer J Physiol Heart Circ, Apr 12 20131, "The Effects of Dietary Flaxseed on Ahterosclerotic Plaque Regression"
2) Drug News Perspect, 2000, 13(2): 99, "Flaxseed: A source of hypocholesterolemic and antiatherogenic agents"
3) Nutrition, Metabolism and Cardiovascular Diseases, Sep 2008, 7:497-502, "The effect of a lignan complex isolated from flaxseed on inflammation markers in healthy postmenopausal women"
4) Journal of Cardiovascular Pharmacology, Nov 2009, 54(5):369-377, "Flaxseed and Cardiovascular Health"
6) Applied Physiology, Nutrition, and Metabolism, Oct 2009, 34(5), "Experimental and clinical research findings on the cardiovascular benefits of consuming flaxseed"
7) Atherosclerosis, Feb 2998, 136(3):367 375, "Reduction of hypercholesterolemic atherosclerosis by CDC-flaxseed with very low alpha-linolenic acid"
8) British Journal of Nutrition, Jun 2008, 99(06), "Dietary flaxseed lignan extract lowers plasma cholesterol and glucose concentrations in hypercholesterolaemic subjects"