Caffeine and fertility

When we talk about caffeine, most people’s first thought is coffee. However, caffeine is found in many other drinks too such as black and green tea, soft drinks, energy drinks and even in chocolate.

Caffeine is a natural stimulant and concerns have historically existed about its effects on our health with suggestions that it can increase the risk of certain conditions such as cancer and cardiovascular disease as well as anxiety. Recent evidence suggests that consumption of 3-5 cups of coffee per day could reduce the risk of some conditions such as type 2 diabetes, cardiovascular disease and some cancers. Coffee contains many other biologically active compounds besides caffeine that may also be protective for health such as antioxidants and some vitamins and minerals, remembering that coffee beans come from a plant. The current UK guidelines recommend that adults can safely consume up to 400 mg/day of caffeine (around 4 cups of coffee). Caffeine can cross the placenta therefore pregnant women in the UK are recommended to limit intake to 200 mg/day. This raises the question of whether we should be conscious about reducing the amount of caffeine we consume while trying to conceive.

A relatively large amount of research has been conducted on the effects of caffeine on fertility. In 2017 researchers analysed data from 35 published studies that had assessed the effect of caffeine on the potential to reproduce, spontaneous abortion and medically assisted reproduction. The analysis found that there was no clear association between exposure to coffee/caffeine and natural fertility as measured by time to pregnancy for 100 or 600 mg/day. A small but significant increased risk in spontaneous abortion was however found with consumption of 300mg/day and 600 my/day. The same 2017 analysis found that there was no association between coffee or caffeine intake and outcomes of fertility treatment. Further evidence from a 2019 study backs this up suggesting that coffee consumption is unrelated to the chances of attaining a clinical pregnancy through IVF (5) and even suggests that women consuming 1-5 cups per day versus no cups of coffee had a higher probability of achieving a pregnancy or a live birth when receiving intrauterine insemination.

Given the evidence above, low to moderate coffee consumption does not appear to negatively affect the success of natural or assisted fertility treatment, however, as more research is required to understand the effect of caffeine on early pregnancy women are recommended to limit intake to while trying to conceive.

The effect of caffeine on male fertility has also been a subject of much research with similarly inconsistent results. A systematic review published in 2017 assessed 28 studies looking at the effect of caffeine on male fertility. They found that semen parameters such as count, motility, morphology and volume did not seem affected by caffeine intake in the form of coffee, tea and cocoa drinks. However, a negative effect was found between cola beverages and caffeine-containing soft drinks on sperm volume, count and concentration. Caffeine intake was also associated with abnormalities in sperm DNA. Research into effects on IVF outcomes suggests however that moderate caffeine intake does not appear to have a negative impact. Much more research is required to further understand the effect of male caffeine intake on fertility, but given the currently limited and inconsistent knowledge, men may want to limit caffeine to 200-300mg/day. So, what does this mean for safe caffeine consumption whilst trying to conceive?

As some research suggests, caffeine may not influence fertility for some, but for others, it could. Some suggest a precautionary intake of below 200mg per day in line with the guidance for pregnancy, which could be a sensible guideline to follow for both women and men who are trying to conceive.

To help you to put this into practice, here are some caffeine values for different foods and drinks.

• Mug of filter coffee 140mg
• Mug of instant coffee 100mg
• Energy drink (250ml) 80mg
• A cup of tea 75mg
• Espresso 75mg
• Can of cola 40mg
• Bar of plain chocolate 25mg
• Bar of milk chocolate 10mg

We require more research before we can confidently understand what effect caffeine may have for both male and female fertility as well as during early pregnancy. From what we know currently, being mindful about your overall diet during the preconception period is important as well as keeping an eye on your caffeine content.