This is one of those books that should be on your nightstand and read until you have it memorized - it's that important. Dr. Gould does something day in and day out that is supposedly impossible: reverse arterial plaque. Right now cardiovascular disease is the number one killer of men and the success of Viagra and Cialis prove that it is the number one killer of erections as well. Think about this: this entire book is essentially devoted to helping you clear out your penile arteries and increase blood flow. Actually, he doesn't word it that way, but that is the net effect.
Sure, testosterone and estradiol are important, but you can have pretty low testosterone and great erections if you have good blood flow and clean arteries. I have seen many men on the The Peak Testosterone Forum that can attest to this. In fact, I was very likely low testosterone all my adult life - never had a morning erection - and yet I had good erections until my late 40's when - very likely anyway - I started developing some arterial issues down under.
And the book starts out early with a real attention-getter: study after study after study that shows that men in Western societies have significant arterial plaque (atherosclerosis) in their 20's and 30's. Most of the young guys - and we have a lot of them - that show up on The Peak Testosterone Forum assume that their issues are strictly hormonal. Of course, sometimes they are, but that is actually a huge assumption on their part.
Let me give you just a couple of examples from the book:
1. Trauma Victims. 76% of men with an average age of 26 had atherosclerosis. 
2. Korean War Veterans. 77% of men with an average age of 22 had atherosclerosis. 
Now, in fairness, he lists other studies on young men that are closer to 50%. Regardless, these are stunning numbers: somewhere between a half and three fourths of all young men already are building plaque in their veins.
What does that have to do with erections? Remember that you can have a little plaque in your neck (carotid) or heart (cardiac) arteries and not feel a thing, because these arteries are so wide. However, the penile arteries are a different story: they are much smaller and even a little plaque can lower nitric oxide and affect erections. Again, he has several pages of stats and studies on this and it's a fantastic motivator in my opinion to make sure you are constantly working on your cardiovascular health.
NOTE: You can purchase his book, Heal Your Heart: How You Can Prevent or Reverse Heart Disease , on Amazon
So just how do you reverse arterial plaque according to Dr. Gould? Well, he goes into an extensive discussion about the subject and there are many steps. He outlines a program of primarily diet, supplements/medications, moderate exercise and monitoring. One thing that I really like about his program is that his starting point is a low fat diet, but he does it in such a way that it would be easy for most guys to do. For example, he allows some low fat meats, low fat dairy and just about any low fat protein source. In fact, his emphasis on protein is something that will resonate with most men serious about their health, because, generally, they are into biking, running, weight lifting, etc. - all of which increase protein requirements above the standard baseline. There is a lot to say about his dietary regime and so I will probably cover it in a separate page. That point is that, even if you don't agree with him on every point, you will get a lot of fantastic information out of it.
Sure, those with a Paleo background will not like the dairy. However, they will appreciate the facts he strongly encourages men to cut back on carbs and carefully watch their triglycerides and HDL. He also demphasizes grains and prefers fruits and vegetables instead - all classic Paleo philosophies.
Dr. Gould also gives lipid guidelines for reversing plaque: he wants total cholesterol < 140; LDL < 90; and HDL > 45. I cover this on my site on Target LDL Levels and Target Trifecta Numbers (HDL, LDL and Triglycerides). Many men will find these numbers very challenging, but it can be easily done and the reward is incredible: getting your arteries back! To achieve these numbers in some men, he will sometimes use a statin or niacin in a manner similar to Dr. Davis. Now his usage of a pharmaceutical is not my favorite idea, but he very carefully explains why he often has to use them, their purpose and how he control for side effects, etc. Again, great information even if one chooses not to go that route. And he has an excellent discussion of the different forms of niacin, dosages, side effects, etc.
Finally, one other interesting point, which contrasts with the position of Dr. Davis from what I understand, it that he likes to use PET scans, instead of the more well-known Heart Scan or Calcium Score emphasized in Track Your Plaque. His argument is that this gives better results regarding blood flow and we all know it's about blood flow, eh?
Again, buy this book and read it and reread it. No amount of any hormone or herb or supplement can help you once those arteries clog up...
1) Heal Your Heart, Dr. K. Lance Gould, Rutgers University Press, 5th Printing 2002, p. 44