STEP 2. Most men simply do not realize the massive difference that boosting your nitric oxide levels can make. You just feel better. You exercise better. You think more clearly. Your blood pressure lowers. And, perhaps best of all, your erectile strength increases. Of course, increased nitric oxide is the house upon which Viagra was built.
Of course, the huge problems that most men over the age of 40 have in the West is the lining of their arteries are now covered with atherosclerosis and scar tissue. And I'll just state the obvious: if your arteries go downhill and arterial plaque lowers your nitric oxide levels, you feel worse. That should come as no surprise. Many men with erectile dysfunction, libido, mental fog and fatigue do not realize how much those would be improved simply by increasing their nitic oxide levels.
Many men try to improve these kind of symptoms with HRT. But HRT is not a miracle cure for atherosclerosis and low nitric oxide levels. That must be worked on separately and there is no substitute for beefy NO levels. Dr. Nathan Bryan has pointed out that many middle-aged men have less than half their youthful nitric oxide levels. Ouch!
And just because you are young, don't think that you are immune. A number of studies have shown young men in their 20's and 30's with very significant artherosclerosis. Sure, you're gonna be better off than most guys in their 60's, but that may not be saying much!
So why not just take a PDE5 Inhibitor and call it a day? Although PDE5 Inhibitors (Cialis, Viagra and Levitra) have had considerable success at raising nitric oxide levels, they are fraught with side effects. Tinnitus, hearing loss, visual disturbances, headaches and my personal favorite: stomach upset and nausea. These medications also can lead to what I call Viagra Resistance and Cialis Dependency. In addition, they do not work that well in men with a lot of arterial plaque. Clearly, there has to be a better way!
This is where more natural solutions can step in and, in most cases, provide excellent results with many less side effects and issues. I go into more detail in my book, The Peak Erectile Strength Diet, but below I give a nice summary of 10+ Ways to Increase Your Nitric Oxide Naturally:
CAUTION: Always check with your doctor before taking any new supplements or even fruit juices if you are on any medications or have any medical conditions.
1. Nitrates (in Foods). There are a number of foods that have high nitrate content, including carrots, lettuce, spinach and, of course, beets. I give substantial coverage to this in my links on Nitric Oxide Replacement Therapy, An Easy NO Boost Through Food, Beet the Odds and Beetroot Juice, but the beautiful thing about nitrates is that they give a man an alternate pathway to raise his NO levels even if he has significant atherosclerosis. The way it works is this: nitrates in one's food are converted to nitrites by the bacteria on your tongue (assuming you haven't killed it all off with mouthwash), which then are converted to nitric oxide in your gut.
NOTE: An even better source of nitrates is arugula - thanks Dr. Greger - and several guys on the Forum including myself swear by the stuff.
The significance of the alternate pathway cannot be overemphasized. Consuming nitrates in your food can give you a nice bump in nitric oxide levels several hours later. The only caution that I have is that nitrosamines in meat and in the environment are considered cancer-causing. And, strangely enough, you can actually end up with nitrosamines in your gut from eating nitrates. This could occur when you combine high-nitrate foods with higher amine foods. However, there is NO evidence that I know of associated any of the above vegetables with cancer - quite the opposite. So most experts that I have read consider this a non-issue. However, if you want to play it safe, simply avoid higher amine foods within a couple of hours when you eat you higher nitrate foods.
2. Citrulline. Citrulline is one of the more recent erectile supplement superstars. Of course, it's been around awhile, but it suddenly dawned on everyone that this was a nice way to boost arginine levels without The Potential Side Effects of Arginine. Basically, what I have read is that taking Citrulline bypasses the normal metabolic pathways and, again, allows men with significant atherosclerosis to gain some of their nitric oxide back by bypassing the normal arterial pathway. Quite a few men on The Peak Testosterone Forum swear by Citrulline and take 1.5-3 g/day. (Always talk to your doctor first.)
The research has really backed this up by the way: one study on senior men showed that taking 5 grams daily improved the stiffness of their arteries. Nice! These were healthy senior men, and this study also showed that arterial stiffness was improved independent of blood pressure.  Yet another study in the following year verified these promising results directly in erectile dysfunction patients by showing that half of study participants increased their hardness factor significantly by taking only 1.5 grams/day of L-Citrulline daily.  Again, these were senior men (average age 57 years) and, it should be noted, that their frequency of intercourse increased as well. What else could you ask for, eh?
3. Pomegranate Juice. Pomegranate Juice is the new heavy weight juice when it comes to improving your bedroom prowess. And part of the reason is that it is a darn good nitric oxide booster. It also lowers blood pressure, improves your cholesterol and, at least in some patients, clears out plaque! For more information, see my link on The Many Benefits of Pomegranate Juice. CAUTION: Pomegranate juice can interact negatively with some medications, including Viagra (and perhaps other PDE5 Inhibitors).
CAUTION: Erectile supplements should be combined very carefully and with the lowest dosage possible, because they can interact negatively with certain medications and medical conditions, and could potentially cause priapism, an erection that does not go away and can damage the penis permanently. See my link on Common Causes of Priapism for more information on the latter. If you ever have an erection that will not go away after an hour or two, go to the E.R. immediately. Example: There have been several cases of pomegranate juice combined with Viagra leading to priapism.
4. Avoid High Fat Meals. Here is a quote from the lead author of a study on walnuts and olive oil: "The inner lining of the arteries produces a substance called nitric oxide that is needed to keep the arteries flexible," Dr. Ros said. "When we eat high-fat meals, the fat molecules temporarily disrupt the production of nitric oxide, preventing the arteries from increasing blood flow in response to physical activity."  The authors go on to explain that the higher fat in the meals creates an inflammatory response that walnuts (and not olive oil) can overcome. Walnuts have both arginine, ALA and various antioxidants in them that actually helps overcome this arterial stiffness that follows a higher fat meal.
Low carbers may wonder if this applies to them. Actually Low Carb does fairly well, according to a couple of studies I have seen, as long as you are losing weight. However, the minute that you are on maintenance, i.e. no longer losing weight, you lose blood flow, vasoreactivity and, therefore, nitric oxide according to one study.  The moral of the story is that over the long haul you want to avoid high fat meals. I outline many other issues in my link on The Dangers of a High Fat Meal, which includes a discussion of lowering testosterone.
5. Vitamin C. Many men do not realize that Vitamin C can relax arteries by a different mechanism: it protects your precious nitric oxide from being destroyed by free radicals.  Further evidence of Vitamin C's powers in this regard are it's ability to lower blood pressure and reduce arterial stiffness. (CAUTION: One study showed that Vitamin C actually constricted arteries. However, this is when combined with another powerful antioxidant, so it is uncertain how applicable it is to practical situations. See my link on Antioxidants and the Heart for more information.
6. CoQ10. If you are hypertensive, have diabetes (and probably prediabetes), CoQ10 is a proven improver of blood flow and lowerer of blood pressure. For example, one meta-analysis of hypertension studies came to the incredible conclusion that "coenzyme Q10 has the potential in hypertensive patients to lower systolic blood pressure by up to 17 mm Hg and diastolic blood pressure by up to 10 mm Hg without significant side effects."  The effect is so strong that scientists believe CoQ10 must be working on nitric oxide to help preserve it from oxidative stress. Or it may act on eNOS. Either way it can have an excellent effect for many men struggling with E.D. Typical dosages in the studies are in the 100 - 200 mg/day range.
7. Moderate Exercise. Brisk walking, which basically just means over 3.0 mph, is a great way to boost your baseline nitric oxide levels. Of course, exercise increases NO for a couple of hours afterward very significantly, but the practical application is that your overall nitric oxide levels can increase as well as long as you do it daily for around 30+ minutes. See my link on The Benefits of Brisk Walking for the research. (It unstiffens arteries and lowers blood pressure also!) And, of course, other forms of exercise can help as well. I just mention brisk walking, because it is so well studied and avoids overtraining, a big issue for many men (including myself from time to time).
8. Ginseng. One supplement that has a successful erectile dysfunction study under its belt is Korean Ginseng. This herb has been used for centuries for many medical conditions, and scientists have found one of its secrets: it does a nice job of increasing nitric oxide. I cover this in detail in my link on Erectile Dysfunction and Ginseng. NOTE: Ginseng can thin the blood a bit, so always talk to your doctor if you are on any medications.
9. Pycnogenol. Pycnogenol, which is a standardized extract of French maritime pine bark, is another supplement with a successful erectile dysfunction study. It works by increasing the activity of eNOS, the enzyme that Viagra and Cialis act upon.  For more information, see my page on Pycnogenol and Erectile Dysfunction.
10. Saturated Fat. One of the big controversies on health blogs and even among experts centers around how much saturated fat really contributes to heart disease. But here is one thing that most of the men arguing on both side of the discussion do not realize: saturated fat very often lowers nitric oxide. One study summarized this issue by saying that "because diets with a high saturated fat content induce high plasma fatty acid levels, endothelial nitric oxide production is often impaired due to a reduction in nitric oxide synthase 3 phosphorylation." 
This is one of the primary reasons that a high fat meal, as mentioned above, also usually lowers nitric oxide levels. Remember: you don't need saturated fat to boost your body's cholesterol levels, because your body makes its own just fine without you sucking down modern oils and butters and corn-fed cows and pigs. Also, virtually every primal culture on planet earth, regardless as to how much meat they consumed, had total cholesterol below 150 and they are much, much healthier than us.
TIP: A lot of people like the taste of olive oil and it's part of Mediterranean cuisine. However, olive oil will actually reduce nitric oxide in many cases and canola oil will not. Furthermore, canola oil is much better regarding inflammation than olive oil. 
11. Raw Cocoa or Dark Chocolate. The flavonoids in dark chocolate or raw cocoa can significantly raise nitric oxide levels. For example, one study gave 44 hypertensive seniors just 30 grams of dark chocolate - a fraction of the typical chocolate bar - and found that it significantly lowered their blood pressure. 
As I point out in my link on The Kuna People, they have incredibly low rates of hypertension and they are regular consumers of raw cocoa. This is the surest way to make sure that you get your flavonol content as processing can reduce flavonols. By the way, the Kuna have average blood pressure readings of 110/70 and very little increase with age!  For more information, see my page on Raw Cocoa Powder.
NOTE: Hopefully, you're noticing a pattern here: many, many plant foods increase nitric oxide and animals are either neutral or lower nitric oxide, depending on their saturated fat content. This is why the DASH Diet, a clinically proven way to eating to lower blood pressure in hypertensive patients, is almost entirely plant-based.
12. Quercetin. This phytochemical is found in many plants, particularly citrus fruits, onions, apples, parsley, wine and tea. It works to boost nitric oxide by decreasing a peptide called endothelin-1. Endothelin-1 is a very strong vasoconstrictor and is actually released by the cells in your endothelium and quercetin controls this effect. 
13. Icariin (Horny Goat Weed). Horny Goat Weed has also been used for centuries to help erectile dysfunction and the primary component with it has been found to contain a natural PDE5 inhibitor called Icariin. There are now extracts of Icariin in the 40+% range, which is usually desirable because Icariin is much less powerful gram-for-gram than the pharmaceutical Viagra. (I have read 50 times less so.)
Again, there are many other fruits, fruit juices, drinks and vegetables that I cover in my book that will help you increase nitric oxide levels. But, again, the key is to eat a well-rounded plant-based diet packed with a variety of fruits and fruit juices.  Yes, you can eat some meat. However, if you are a bit older and your endothelium is damaged, you will find that you do much better following some of the tips above.
TIP: Did you know that just one cup of raisins can lower blood pressure (and slash TNF alpha levels)? Anything with grapes - even many wines - can do the same thing.
REMEMBER: Being overweight, being sedentary and smoking hammer your endothelium. All the food and supplements in the world cannot overcome these.
1) Int J Cardiol, 2010 Nov 8, "Short-term effects of l-citrulline supplementation on arterial stiffness in middle-aged men"
2) Urology, 2011 Jan, 77(1):119-22, "Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction"
3) http://www.sciencedaily.com/releases/2006/10/061010022750.htm, "Eating Walnuts With High-Fat Meals Helps To Protect Arteries Against Short-Term Damage"
4) Circulation, 2007; 116:II_819, "Abstract 3610: Comparative Effects of 3 Popular Diets on Lipids, Endothelial Function and Biomarkers of Atherothrombosis in the Absence of Weight Loss"
5) Journal of Biological Chemistry, 274, 8254-8260, "L-Ascorbic Acid Potentiates Nitric Oxide Synthesis in Endothelial Cells"
6) Journal of Human Hypertension, 2007, 21:297 306, "Coenzyme Q10 in the treatment of hypertension: a meta-analysis of the clinical trials"
7) Curr Opin Clin Nutr Metab Care, 2010 Jan, 13(1):97-104., "Regulation of nitric oxide production in health and disease"
8) JAMA, 2007 Jul 4, 298(1), "Effects of Low Habitual Cocoa Intake on Blood Pressure and Bioactive Nitric Oxide: A Randomized Controlled Trial"
9) Lipids Health Disease, 2008, 7(14), "Raisins and additional walking have distinct effects on plasma lipids and inflammatory cytokines"
10) Int J Med Sci, 4(1):253-258, "Does Flavanol Intake Influence Mortality from Nitric Oxide-Dependent Processes? Ischemic Heart Disease, Stroke, Diabetes Mellitus, and Cancer in Panama"
11) International Journal of Clinical Pharmacology and Therapeutics, 2002, 40(4):158-168, "A review of the French maritime pine bark extract (Pycnogenol), a herbal medication with a diverse clinical pharmacology"