Caffeine is the world’s most used psychoactive drug. In Australia, most of the caffeine consumed in Australia comes from coffee, tea and caffeinated soft drinks.
Caffeine is absorbed into the bloodstream and reaches the brain very quickly. It acts as a stimulant by blocking adenosine receptors in the brain, which usually promote relaxation and sleepiness. Caffeine stimulates the sympathetic nervous system, which is how it increases heart rate and blood pressure, and it increases the availability of calcium in muscle cells, which enhances muscle contractions. These effects of caffeine last for a few hours after consumption.
Caffeine also stimulates sperm, as shown by an increase in the proportion of sperm with effective movement and possible improvements in the fertilising ability of sperm when caffeine is added to sperm in laboratory experiments.
If you have too much caffeine its effects on your body are stronger, resulting in feelings of restlessness, irritability, nervousness and ‘the jitters’. An irregular or racing heartbeat, sleep problems, headache, dizziness, stomach upset and muscle twitches can also occur. Similarly, high doses of caffeine in laboratory experiments have bad effects on sperm.
Drinking a moderate amount of coffee (up to five cups per day, a total of up to 400 mg caffeine), or an equivalent amount of tea (six to 10 cups), is not associated with changes in men’s semen quality and seems to have no effect on fertility. Some studies show associations between coffee drinking and damage to the DNA in sperm but other studies do not, so there’s really not enough evidence to be sure. If you get your caffeine from soft drinks though, sperm quality and the probability of getting your partner pregnant may be impaired, perhaps because of the sugar and not the caffeine.
There’s no reason to be concerned that your caffeine consumption might be damaging your sperm and limiting your ability to have children, and there’s no evidence to suggest that you should stop drinking a few cups of coffee each day if you’re trying to start a family.
Tim Moss
Healthy Male Health Content Manager
Associate Professor Tim Moss has PhD in physiology and more than 20 years’ experience as a biomedical research scientist. Tim stepped away from his successful academic career at the end of 2019, to apply his skills in turning complicated scientific and medical knowledge into information that all people can use to improve their health and wellbeing. Tim has written for crikey.com and Scientific American’s Observations blog, which is far more interesting than his authorship of over 150 academic publications. He has studied science communication at the Alan Alda Centre for Communicating Science in New York, and at the Department of Biological Engineering Communication Lab at MIT in Boston.
