In answer to a reader's query on whether it was dangerous to swallow sperm, Health24's former sexologist, Dr Elna McIntosh, wrote the following answer:
A typical ejaculation fills up about one teaspoon; the actual amount is determined by a man's age (younger men usually make more semen), when a man last ejaculated, and how long he's aroused before ejaculating, among other factors.
Contrary to what you've heard, semen is not loaded with kilojoules. Each teaspoon of ejaculate has about 21 kilojoules and some 200 - 500 million sperm. Since sperm make up only about 1% of semen, what accounts for the other 99%? Well, its other ingredients include:
Ascorbic acid (a.k.a. vitamin C)
Phosphate and bicarbonate buffers (bases)
Can swallowing semen enrich a poor diet? Unless you're gulping gallons of it each day, it's no substitute for real nutritious cuisine.
Kilojoules aside, if it's semen (the liquid in which sperm exits the penis) that you're worried about, all the safer sex guidelines apply when you swallow someone else's semen. There's still debate about HIV transmission via semen and oral sex, but there are plenty of other sexually transmitted infections (STIs) that can be passed along by oral sex, too. - (Health24, January 2012)