The benefits of popcorn for us guys are many and can even extend into the bedroom. Of course, I am assuming that you leave off the copious amounts of butter, fat, salt and excitotoxins that people typically put onto their popcorn. Natural popcorn that is lightly salted, though, is a great snack and below I give you three erection-promoting reasons why:
1) Nitric Oxide. Popcorn is a great source of L-Arginine. For example, let's say that you have 240 calories of popcorn or 2 ounces (56 grams). This will supply you with a reasonable 42 grams of carbohydrate and, most importantly, about 340 mg of all-natural Arginine.  Furthermore, popcorn has a favorable Arginine-to-Lysine ratio, which means that the popcorn will ramp up the powerful nitric oxide, blood-dilating pathway.
Will popcorn lower your blood pressure and cure your erectile dysfunction? No, of course not, but it is one of many foods that, when put together as a complete dietary regimen can make a big difference in how you feel and even how you can perform in the bedroom. (For more erectile-boosting foods, see my book The Peak Erectile Strength Diet.)
Contrast this will foods like refined sugars and breads and How and Why Saturated Fat Can Be Bad For You, which will hammer nitric oxide and slow down blood flow. Popcorn is the opposite: a food you can eat with confidence before heading to the bedroom.
2) Testosterone Maintenance. Popcorn is certainly not going to boost your testosterone. However, many snacks will likely lower your testosterone a little. The reason? As you know from my link on Testosterone and Glucose, high glycemic foods will likely lead to a post-meal drop in testosterone that last for several hours according to the latest research. However, straight air-popped popcorn only has a Glycemic Index of 55 and a very low Glycemic Load - around 6 for a standard serving.
In other words, popcorn is very unlikely to bump up your blood sugar and insulin because it is relatively filling and relatively slow to hit the blood stream.
3) Minerals. Another surprising benefit of popcorn: it has a nice balance of nutrients that will bolster your energy, strength and health in general. Yes, popcorn has received a bad reputation over the years, but that's largely because of all the "extras" that people put on it. Under the covers, popcorn is a very nutritious food that is literally a mini-vitamin pill.
Consider that fact that three cups of air-popped popcorn will supply you with 0.9 grams of Zinc. That's about 6% of the RDA (15 grams) and is very absorbable, unlike many of the zinc supplements out there.  In my link on The Benefits of Zinc, I discuss how Zinc can be a big help with testosterone and other sexual health-related issues.
The same amount of popcorn will also supply you with about 32 grams of Magnesium , or almost 10% of your RDA, which can help with sleep, cardiovascular health and, potentially, a little with erections as well.
CAUTIONS: There are a few, relatively minor in my opinion, cautions associated with popcorn:
1. Genetic Modification. Corn, in general, is a significantly GMOed food, i.e. it's genome has been altered in the last fifty years or so to increase yield, durability and other issues. In my link on Wheat Belly, I outline how this has become an issue with wheat. Fortunately, it does not yet appear to be as much of an issue with corn.
2. Diverticulitis. Also, some experts have asserted that popcorn (and possibly nuts) could increase the risk for diverticulitis. However, one large study found this not to be the case.  Talk to you physician, though, with any concerns.
3. Chemicals. Microwave popcorn can spread a minute residue of a toxic chemical called PFCAs, the best known of which is perfluorooctanoic acid (PFOA).  Is this enough to cause health issues? No one knows the answer yet, but it may be prudent to make your popcorn the old-fashioned way.
4. Herpes. One of the benefits, the boost in Arginine levels, coming from eating popcorn could, for some men, be a curse actually. The reason is that in some sensitive men, raising the L-Arginine to L-Lysine ratio of their diet will result in herpes infection outbreaks. .
3) 46) JAMA, 2008, 300(8):907-914, "Nut, Corn, and Popcorn Consumption and the Incidence of Diverticular Disease"