Boys who eat junk food might damage fertility for rest of life
Male fertility is being irreversibly damaged by a diet of junk food by the time men reach 18, a study has found.
A new investigation has established that teenagers who favour high-fat and processed foods such as pizzas, chips and snacks are killing off sperm-producing cells that can never be replaced.
It also showed that a diet dominated by fish, chicken, vegetables and fruit is best for protecting those cells and ensuring healthy sperm levels.
Sperm counts have been declining in recent decades, and various studies have pointed to poor diet as a significant cause. However, they tended to focus on those in their late 20s, 30s and 40s who are struggling to conceive.
By contrast, a new Harvard University investigation shows for the first time that poor diet while growing up may reduce a man's chances of fathering children for the rest of his life.
Prof Allan Pacey from the University of Sheffield, a leading authority on sperm, said: "The concern would be that poor diet younger in life makes a change that sticks with you."
The Harvard researchers accessed the data of nearly 3,000 men who had a medical examination upon starting national service in Denmark. The average age was 19.
From the responses to a dietary questionnaire, four types of diet were identified: a "Western" diet characterised by red meat, processed meat, fatty and sugary food and drink; a "prudent" diet comprising mainly chicken, fish, vegetables and fruit; a "Smorrebrod" diet of cold processed meats, whole grains, mayonnaise, cold fish, condiments, and dairy; and a vegetarian diet, involving lots of vegetables, soya milk and eggs.
Sperm health, as measured by concentration, volume and motility, was best in those following the prudent diet, followed by the vegetarian and then Smorrebrod diets, with the Western diet yielding the worse readings.
The scientists also conducted hormonal tests indicating the health of sperm-producing Sertoli cells, again finding that these were depleted in the young men who favoured junk food.
It is thought a person cannot recover Sertoli cells killed by oxidative stress, which has implications for the amount of sperm they can produce at any one time.