I’m writing this blog post at the request of my wife, who is troubled by the lack of information available to well-meaning people on the biological consequences of not ejaculating (for men).

There’s an entire month called no-nut November dedicated to this, and it’s common among some spiritual circles to save one’s seed for procreation purposes. Semen retention is literally the most common men’s health content on TikTok and Instagram, with 100% of its engagement coming from non-physicians. It was also rated as being the least accurate type of information shared.

If you want to avoid ejaculation, for whatever reason, then by all means go ahead. I’m not here to argue or debunk whatever reasons people commonly cite; I’m just here to share what we know to be true based on the available research.

What that research seems to consistently show is that semen retention is a really bad idea if you are trying to have a baby. This may be a minority of men, but for those men who are actively trying to have children, semen retention should be avoided, especially if you or your wife already struggle with fertility issues.

A recent systematic review of 24 studies found that, of the 13 reporting on pregnancy rates, every single one reported higher pregnancy rates with shorter abstinence periods, although statistical significance was achieved in just 9 of them. Of 3 studies reporting on live birth rate, all found higher rates with shorter abstinence periods. Of 15 studies reporting on DNA fragmentation, all found benefits from shorter abstinence, with statistical significance achieved in 11 studies.

Now, you may be wondering how this is possible. After all, an IVF study using ICSI, where 95% of men had abnormal semen parameters, found that abstinence length was positively correlated with semen volume, sperm concentration, sperm count, and motile sperm. That’s good for fertility, right?

Well, that same study also found that greater abstinence time was associated with more DNA fragmentation within the sperm, worse fertilization rates, fewer blastocyst formation on day 5, lower implantation rate, and lower pregnancy rate (no association with miscarriage rate).

A meta-analysis of 13 studies confirmed most of these observations, showing that greater abstinence times were associated with greater sperm counts and semen volume, but also greater DNA fragmentation and lower progressive motility (the number of “good swimming” sperm).

The researchers determined that the most plausible biological mechanisms for these observations was that the reduced epididymal transit time resulted in less oxidative stress and epigenetic modifications, leading to better sperm quality.

There’s a lot more research than what I’ve discussed, but I feel that the studies I’ve shared summarize and illustrate the topic sufficiently. Semen retention hurts sperm quality and the likelihood of pregnancy. You should abstain for no more than 24 hours to maximize sperm quality if you are trying to have a baby.

As an aside, since we are talking about fertility, men have more degenerate sperm as they age. A systematic review of 19 studies found that 17 of them reported a significant association between older men and higher rates of sperm DNA fragmentation. Since sperm do much more than just supply half the DNA of the new human, having more fragmented sperm can really mess up fertilization and embryo development (i.e., old dads can increase the risk of birth defects).

I think it’s also worth pointing out that semen retention likely increases the risk of prostate cancer. In one of the largest studies investigating this, which involved nearly 32,000 men followed for 20 years, ejaculating more than 21 times per month was associated with a 19–22% lower risk of prostate cancer compared to ejaculating 4–7 times per month, with the risk reduction being similar among 20- and 40- year-old men. The protective effects were seen in those with low to intermediate risk of prostate cancer, but disappeared among those at high risk.