The research clearly shows the incredible, nearly miraculous benefits of eating fruits and vegetables. Fruits and vegetables will protect you against the top 3 killers of men as well as the top 3 cancers of men. They will also guard both your brain and body. The benefits range from psychological to cardiovascular to cancer protective and on and on.
Other than possibly exercise, there is nothing that confers this kind of broad range of protection against chronic disease. If they found a drug that could do all of this, it would make front page news. However, a food-based solution seems boring and scarcely any mention is made by the media or the medical profession.
But natural is where it's at and that fruits and vegetables are miracle workers when consumed every day. Elsewhere on the site, I document that they can give an incredible boost to blood flow, nitric oxide and your sex life in general. This is also the subject of my book The Peak Erectile Strength Diet. (You may also want to read about the potential for Higher Testosterone Levels through Plant-Based Eating.)
Right now the Paleo and Low Carb Diets are the rage. But stop and ask yourself, "Where are studies that show that eating beef, chicken, pork, etc. can decrease cancer and cardiovascular risks?" Good question, eh? Well, you can look as long as you want, but they are not there. Again, abundant research, which I document below, shows the benefit of fruits and vegetables, but there is simply no equivalent for you carnivores out there (with all due respect of course).
I occasionally eat meat and have egg whites nearly every day, so it is not "religious" with me. But I long ago realized that the benes are with fruits and vegetables. This is Nature's Sweet Spot and it can make all the difference. Sure, there are a few supplements that are probably absolutely essential due to the conditions of modern living, such as vitamins C, D and the omega-3's. But there is nothing more powerful than plant-based eating and I'll show why below with The Top 15 Benefits of Eating Fruits and Vegetables:
1. Happiness. This says it all. One study clearly shows the greater the fruit and vegetable consumption, the greater one's happiness.  That's because fruits and vegetables are so brain-protective and brain-building. They do just what the brain needs: supply a wide array of vitamins and minerals, bathe neurons in antioxidants, increase blood flow, protect against stroke - the list could on and on.
In fact, if your mood isn't where it should be, one of the first places you should look is on your plate. the study that showed the above examined mental well-being and mood from a wide variety of states and confounders and still found a dose-dependent relationship up to 7-8 servings of fruit and vegetables. Yes, you just can't get enough of them!
2. Cardiovascular Disease. What is the number one killer of men (and women)? Most of us know that it is heart disease. And what has been shown in study after study to reduce this risk? Yes, fruits and vegetables. How do fruits and vegetables work their magic? It's simple - they lower almost every known risk factor for cardiovascular disease. Look at what these researchers wrote: "Recent large, prospective studies also show a direct inverse association between fruit and vegetable intake and the development of CVD incidents such as coronary heart disease." 
3. Erectile Dysufnction. Peak Testosterone readers know how intimately heart disease and erectile dysfunction are tied together. "As the arteries go, so goes the penis" is a good motto to keep in mind. So it will be no surprise to find that fruit and vegetable consumption is correlated with male erections. 
4. Stroke. If there is one thing that can instantly change your life, it's a stroke. And mini-strokes can hammer the brain and destroy cognition later in life. Research, including the well-known Framingham Study, has repeatedly shown that fruits and vegetables protect against all types of strokes. 
5. Mortality and Survival. Want to increase your chance of surviving another decade? Well, guess who are some of your truest friends? As expected, fruit and vegetable consumption has been found to be associated with decreased cardiovascular, cancer and all cause mortality. 
6. High Blood Pressure (Hypertension). A huge risk factor for erectile dysfunction, stroke, heart disease and dementia is high blood pressure. Of course, fruits and vegetables have been shown in several studies to be associated with lower blood pressure.  It's no wonder then that the plant-based DASH and Low Fat Diets are proven blood pressure lowerers. See my link on The Benefits of Low Fat Diet for more details.
7. Diabetes. Several studies have shown that fruit and vegetable consumption can protect against the development of Type II diabetes.  Adult onset diabetes is a huge risk factor for just about every chronic disease that plagues modern society and accelerates aging in general.
8. Dementia. One of the scariest things to think about is losing your ability to remember, think and converse. Once again, fruits and vegetables come to the rescue, significantly reducing your risk of dementia. 
9. Inflammation. As I often write, "Inflammation is the root of all evil." And it truly is, being the root cause for heart disease, autoimmune disorders, many cancers and Alzheimers. Well, one study found a dose dependent relationship between fruit and vegetable consumption and CRP levels (C-Reactive Protein), a broad-based measure of systemic inflammation and a strong risk factor for heart disease. Dose dependency is a very good sign of the accuracy of a study and, in this case, meant that the more fruit and vegetables eaten on a daily basis, the less the levels of inflammation. 
10. Colon Cancer. The big three cancers for men are prostate, lung and colon. [9) Wonder why I mention it? That's right - fruit and vegetable consumption are inversely correlated with colon cancer risk. Interestingly enough fruit, which gets a bad rap from the Low Carb and carnivore crowds often, conferred the highest protection. 
11. Lung Cancer. One of the biggest man killers is lung cancer. And don't be fooled: non smokers can get lung cancer surprisingly easily. Air pollution and can contribute to risk for nonsmokers but the second leading cause for lung cancer is radon. Many of us have been exposed to radon and have no idea, but the effects show up later as lung cancer. What is one of your best protections? You got it: fruits and vegetables. Many studies have shown this. One interesting thing came out of a meta-analysis: fruit actually likely conferred the greatest protection. 
NOTE: I talk a lot about the risks of fructose consumption. However, looking at #10 and #11, fruit is so protective of these major killers, I cannot help but conclude that all the incredible benefits of fruit far outweigh the risks of the extra fruit. I do believe some people are sensitive to fructose and many experts recommend that you keep your totally daily fructose in the 25-50 gram/day range. For more information, see my header page on Fructose Consumption. And, whatever, you do, do not consume High Fructose Corn Syrup or table sugar (which is half fructose).
12. Prostate Cancer. (Cruciferous) The most powerful vegetable-related cancer protection for men probably comes from broccoli. Fruit and vegetable consumption is protective, but primarily through consumption of cruciferous vegetables (broccoli, cauliflower, etc.) and several studies have shown this effect. 
NOTE: Whole grains have been getting a lot of negative press lately. And I am very cautious about Modern Wheat and Soy. Nevertheless, most whole grains are powerhouses, a fact I document on Whole Grains and Your Sex Life.
13. Homocysteine. A big risk factor for heart disease is elevated homocysteine levels. One study found a dose dependent relationship with homocysteine levels, meaning the more the fruits and vegetables, the less the homocysteine levels. 
14. Oral Cancers. 28 out of 29 studies! 
15. Pancreas and Stomach Cancers. 26 out of 30 studies. 
1) Social Indicators Research, "Is Psychological Well-Being Linked to the Consumption of Fruit and Vegetables?"
2) Current Atherosclerosis Reports, 2003, 5(6):492-499, "Dietary intake of fruits and vegetables and risk of cardiovascular disease"
3) JAMA, 1995, 273(14):1113-1117, "Protective Effect of Fruits and Vegetables on Development of Stroke in Men"
4) International Journal of Impotence Research, 2006, 18:370 374. "Dietary factors in erectile dysfunction"
5) American Journal of Epidemiology 160(12Pp):1223-1233, "Fruit, Vegetable, and Antioxidant Intake and All-Cause, Cancer, and Cardiovascular Disease Mortality in a Community-dwelling Population in Washington County, Maryland"
6) Current Atherosclerosis Reports, 2003, 5(6):492-499, "Dietary intake of fruits and vegetables and risk of cardiovascular disease"
7) Am. J. Epidemiol, 2005, 161 (3):219-227, "Dietary Patterns and the Incidence of Type 2 Diabetes"
8) Neurology, Nov 13 2007, 69(20):1921-1930, "Dietary patterns and risk of dementia The Three-City cohort study*"
10) JNCI J Natl Cancer Inst, 2001, 93(7):525-533, "Fruit, Vegetables, Dietary Fiber, and Risk of Colorectal Cancer"
11) International Journal of Cancer, 20 Dec 2003, 107(6):1001 1011, "Fruits, vegetables and lung cancer: A pooled analysis of cohort studies"
12) Nutrition and Cancer, 1992, 18(1), "Fruit, vegetables, and cancer prevention: A review of the epidemiological evidence"
12) JNCI J Natl Cancer Inst, 2007, 99(15):1200-1209, "Prospective Study of Fruit and Vegetable Intake and Risk of Prostate Cancer"
13) JNCI J Natl Cancer Inst, 2000, 92(1):61-68., "Fruit and Vegetable Intakes and Prostate Cancer Risk"
14) J Nutr, 2004, 134:913-918, "Plasma C-reactive protein and homocysteine concentrations are related to frequent fruit and vegetable intake in Hispanic and non-Hispanic white elders"