Is Coffee or Tea Bad for Sperm?

In short, maybe.

A new study from the US National Institutes of Health surprisingly found men with moderate coffee or tea intake (2 cups/day) are more likely to impregnate their partner vs men who don't drink coffee or tea. The mechanism is hypothesized to be the effect of caffeine on the sperm cell's metabolic molecules Adenosine Triphosphate (ATP) and Guanosine Triphosphate (GTP). Caffeine prevents ATP and GTP from breaking down, so more energy is available to sperm to swim faster or longer.

But hold on! The above study focused on conception only, not carrying to term. The IVF data provides some more insights even for those looking to conceive naturally.

In a recent study done in Boston, men who drank 2.7 or more strong cups of coffee (>272mg/day) had just a one in five chance of a successful IVF birth per cycle, while men who drank 1 or less cups of coffee (<99mg/day) had a 52% chance of success. Interestingly the study could not see differences in sperm count, shape, or motility between the two groups. So why the reduced success rate?

The leading hypothesis is that caffeine causes DNA damage, either directly or via sleep or hormone dis-regulation. A 2007 study found that, independent of age, healthy non-smoking men whose daily caffeine intake amounted to >308 mg (∼2.9 cups) have shown increased double-strand sperm DNA damage.

Putting it all together:

• Moderate caffeine intake may improve the ability of sperm to swim, making them more able to reach the egg.
• Caffeine intake may damage sperm DNA. 

Conclusion

• When trying to conceive, aim for 2 or fewer cups of coffee/tea per day.
• If you already drink less, do not increase your coffee/tea consumption.
• More study is necessary to determine the tradeoffs in the 0-2 cups/day region.