The rule that governs all the others
Spermatogenesis takes roughly 72 to 74 days from stem cell to mature sperm, plus around two more weeks of maturation in the epididymis.
Everything else on this page depends on that number. The sperm in a sample today was set in motion around three months ago. Clean up your lifestyle the week you start trying and you will be conceiving with sperm produced under the old conditions.
Lifestyle changes should start at least three months before you want to conceive, and ideally three to six, particularly for smoking and weight where the change itself takes time to complete. Our guide to the 3-month rule covers the timeline in detail.
Treat the months before trying as a pre-season. That framing is useful, because it sets the expectation that this is preparation with a deadline rather than a permanent regime.
Rule 1: Get your weight into a healthy range
Excess body fat affects sperm through hormones rather than directly. Adipose tissue converts testosterone into oestrogen via the aromatase enzyme, which shifts the hormonal balance away from what sperm production requires. It also raises scrotal temperature and increases systemic oxidative stress.
The effect is dose-related. A systematic review and collaborative meta-analysis in Human Reproduction Update examining BMI in relation to sperm count found higher rates of oligozoospermia and azoospermia among overweight and obese men compared with those of normal weight.
The encouraging part is that this is reversible. Weight loss and increased physical activity improve testosterone production and spermatogenesis, which puts weight near the top of the list of things actually worth your effort.
Rule 2: Train regularly, but do not under-fuel
Regular moderate exercise supports healthy weight, cardiovascular function and hormonal balance. That is the straightforward part.
The complication is that more is not automatically better. Combining a very high training load with insufficient food and recovery can push things in the opposite direction. Relative Energy Deficiency in Sport describes what happens when an athlete consistently fails to consume enough energy to support both training and normal physiological function. In men, this can suppress the hypothalamic-pituitary-gonadal axis, reduce testosterone and impair sperm production.
The practical version: train, eat enough to support the training, and if you are in a deep cut while trying to conceive, reconsider the timing. Our piece on physical labour and sperm health covers the related question of heavy manual work.
Rule 3: Stop smoking, and treat vaping as unresolved
The WHO published systematic reviews on tobacco and fertility in September 2026, pooling 44 studies of more than 60,000 men. Men who smoke show higher rates of erectile dysfunction, ejaculation problems, poor sperm motility, abnormal sperm shape and absence of sperm in the ejaculate. Across 21 studies of assisted reproduction, smoking was linked to roughly half the chance of a successful outcome.
A 2016 meta-analysis in European Urology covering 5,865 men put numbers on it: sperm count reduced by 9.72 million per millilitre, motility by 3.48 percentage points, morphology by 1.37 points, with larger effects in moderate and heavy smokers.
Recovery is real and reasonably quick. In one cessation study, men who quit after smoking 20 or more a day saw total sperm count rise from 45 million to 65 million at around three and a half months. Our full guide to smoking and sperm quality covers the mechanism and the recovery timeline.
On vaping, the evidence is thinner. A 2020 study in Human Reproduction found daily e-cigarette users had a median total sperm count of 91 million against 147 million in non-users, similar to daily smokers. It is cross-sectional, so association rather than proven cause. Being nicotine-free for the three months before conception remains the safer plan.
Rule 4: Keep alcohol and recreational drugs out of the window
Chronic heavy alcohol consumption lowers testosterone and adversely affects sperm concentration, motility and morphology. Occasional moderate drinking has much weaker evidence against it, and the guidance most clinicians give reflects that difference rather than demanding total abstinence.
Cannabis has been associated with reduced sperm concentration and abnormal morphology, and cocaine with reduced motility. These are worth removing from the three-month window regardless of what you conclude about them generally.
Rule 5: Be honest about what supplements can and cannot do
This is where the gap between marketing and evidence is widest, and it deserves a straight answer.
Two large randomised controlled trials have tested the core claim directly.
The MOXI trial randomised 171 men with male factor infertility to a combined antioxidant formulation containing vitamin C, vitamin E, selenium, L-carnitine, zinc, folic acid and lycopene, or placebo. It found no significant improvement in sperm motility, morphology or DNA fragmentation at three months, and no improvement in cumulative live birth.
The FAZST trial was larger, randomising 2,370 couples to 5mg folic acid plus 30mg zinc or placebo for six months. Live birth was 34% in the supplement group and 35% in the placebo group. Sperm concentration, motility, morphology, volume and total motile count showed no significant difference. DNA fragmentation was slightly higher in the supplement group, and gastrointestinal side effects were more common.
Those are the two best trials in the field and both are negative for live birth.
What that does and does not mean. It means no supplement has been shown to reliably improve a couple's chance of having a baby, and any product implying otherwise is ahead of the evidence. It does not mean nutrition is irrelevant to sperm production. Zinc, selenium, folate, vitamins C and E and omega-3 fatty acids all have established roles in spermatogenesis, and genuine deficiency in any of them is worth correcting.
The distinction is between correcting a deficiency, which is sound, and treating a supplement as a fertility therapy in a man who is not deficient, which the trials do not support.
Both trials also enrolled men who were largely well-nourished, which is the most plausible explanation for the null results and a genuine limitation when extrapolating to men with poor diets. That is an argument for eating properly, not an argument for the supplement aisle.
Rule 6: Eat in a way that is boring and well evidenced
There is no sperm-boosting superfood. What the evidence supports is a Mediterranean-style pattern: vegetables, fruit, wholegrains, pulses, nuts, seeds, olive oil and oily fish, with processed food, processed meat, excess sugar and saturated fat kept down.
That pattern is associated with better reproductive outcomes in both partners, and it supplies the nutrients involved in normal sperm production without needing a separate product to deliver them. Our 10 healthy habits for male fertility covers the practical version.
Rule 7: Do not touch testosterone if you want children
For gym-going men, this is the most important item on the page.
Sperm production requires very high testosterone concentrations inside the testes, produced locally under the direction of the pituitary hormones FSH and LH. Taking testosterone from outside suppresses those signals. The testes stop being stimulated, local production collapses, and sperm production can fall dramatically or stop entirely, causing azoospermia and testicular shrinkage.
Blood testosterone rises while fertility falls. Testosterone therapy should not be used by men trying to conceive.
Sperm production may recover after stopping anabolic steroids, but recovery commonly takes six to twelve months or longer, and chronic use can have lasting effects. UK fertility guidance now specifically directs clinicians to ask about testosterone replacement therapy, anabolic steroids and other drugs when a patient raises fertility concerns. Our guide on TRT and fertility covers what to do if this applies to you.
Rule 8: Manage real heat, ignore the rest
The testes sit outside the body because sperm production works best below core temperature. Repeated significant heating does matter, and men actively trying to improve poor sperm parameters are usually advised to avoid frequent or prolonged hot tubs, jacuzzis and saunas.
What does not deserve the same anxiety is the everyday stuff. Whether loose-fitting underwear improves fertility remains uncertain. Recreational cycling has not been shown to cause infertility. Warm car seats are not a documented fertility risk, and neither, on current evidence, is a phone in your pocket.
The evidence for addressing weight, smoking, heavy drinking and inactivity is far stronger than the evidence for worrying about occasional heat exposure. Spend your effort accordingly.
Rule 9: Test rather than guess
Lifestyle optimisation has limits, and the biggest risk is spending a year tinkering with diet and training while avoiding the one thing that would tell you what you are dealing with.
A baseline semen analysis is a simple first step. If there is a problem, identifying it early opens up treatment options and prevents months being lost. If there is not, reassurance is a legitimate and valuable outcome.
Seek advice sooner if you have a history of testosterone or anabolic steroid use, testicular trauma or surgery, undescended testes, a lump or persistent ache, erectile or ejaculatory problems, or previous chemotherapy.
One caveat on interpretation: a semen analysis is not a pass or fail fertility test. It measures volume, concentration, total sperm number, motility and morphology, and results vary naturally and substantially between samples from the same man. Test before you make changes and again after a full production cycle, and read the trend rather than any single number. Our comparison of test types, costs and reliability covers the options.
Frequently asked questions
How long before trying should I start making changes?
At least three months, which covers one full sperm production cycle of roughly 72 to 74 days. Three to six months is better for smoking cessation and weight loss, since the change itself takes time to complete on top of the biological lag.
Do male fertility supplements work?
No supplement has been shown to reliably improve a couple's chance of having a baby. The MOXI trial found no improvement in semen parameters or DNA fragmentation with a combined antioxidant formula, and the FAZST trial of 2,370 couples found live birth rates of 34% with folic acid and zinc versus 35% with placebo. Correcting a genuine nutritional deficiency is worthwhile. Treating supplements as a fertility therapy is not supported by the trial evidence.
Does losing weight improve sperm quality?
The evidence supports it. Excess body fat converts testosterone to oestrogen, raises scrotal temperature and increases oxidative stress, and higher BMI is associated with higher rates of low sperm count. Weight loss and increased activity improve testosterone production and spermatogenesis.
Can too much exercise reduce fertility?
It can, when training load consistently exceeds energy intake. Relative Energy Deficiency in Sport can suppress the hormonal axis that drives testosterone and sperm production. Regular moderate training with adequate food and recovery supports fertility rather than harming it.
Should I switch to loose underwear?
Current guidance acknowledges an association between raised scrotal temperature and reduced semen quality, but whether loose-fitting underwear actually improves fertility remains uncertain. Avoiding frequent saunas and hot tubs has better support. Weight, smoking, alcohol and activity matter considerably more.
How long does sperm production take to recover after stopping steroids?
Commonly six to twelve months after stopping, and sometimes longer. Chronic use can have lasting effects. Anyone in this position who wants children should get a baseline semen analysis and speak to a specialist rather than waiting to see what happens.
The takeaway
The fertility plan that holds up to evidence is not exotic. Reach a healthy weight, train sensibly and eat enough to support it, eat a Mediterranean-style diet, do not smoke, keep alcohol moderate, keep recreational drugs out of the picture, sleep properly, and do not go near testosterone if fatherhood matters to you.
Then measure. For many men the result is reassurance. For others, finding a problem early opens up options and stops valuable time being lost.
The ExSeed home sperm test gives you concentration, motility and total motile sperm count to WHO standards in 15 minutes at home. If you are running a 90-day change, the 5-test kit covers a baseline plus repeats across the cycle, which is what turns guesswork into a trend.
This article is for information only and does not replace medical advice. If you have been trying to conceive for 12 months or more, or six months if your partner is over 35, speak to your GP. Never start or stop prescribed medication based on information in an article.
