Here is a partial list of some of the things found in semen: aboutonia, ascorbic acid, blood-group antigens, calcium, chlorine, cholesterol, choline, citric acid, creatine, DNA, fructose, glutathione, hyaluronidase, inositol, lactic acid, magnesium, nirtogen, phosphorous, potassium, purine, pyrimidine, pyruvic acid, sodium, sorbitol, spermidine, spermine, urea, uric acid, vitamin B12, zinc. An average man's ejaculate contains about 15 calories.
The first thing i noticed about this, other than the low calorie count, was the Inositol. Inositol is a B Vitamin, which was oft publicized as THE B vitamin to cure depression. Apparently, Inositol is one of the key precursors to serotonin. Serotonin, as you may or may not know, is one of the chemicals "responsible" for happiness (SSRI drugs hold serotonin in your brain longer, keping you happy). So, people who swallow a lot of semen are likely to be happier.
In addition, notice trace minerals (calcium, magnesium, potassium and zinc)! These are tough to get in a lot of foods. And the protein is something everyone needs! B12 is another vitamin essential to happiness and health. So, next time, think about the health benefits of swallowing!!