Ultra-processed food may harm men’s heart health and fertility, study suggests

A grocery store aisle in Montreal on Oct. 9, 2024. THE CANADIAN PRESS/Graham Hughes

Ultra-processed foods may harm young men’s heart and reproductive health, even if they don’t eat more calories, new research has found.

Published late last month in Cell Metabolism, the study by an international team of researchers examined the health impacts of different types and amounts of food on a group of 43 men aged 20 to 35.

Ultra-processed foods are products that have been significantly “transformed, derived, or synthesized” during the manufacturing process, and are typically packaged and industrially made. They include things like frozen pizzas, chips, packaged snacks, sugary cereals and soft drinks. In Canada, they make up roughly half of the average person’s diet.

Participants in the study rotated through three-week periods of diets high in ultra-processed food and diets with almost none at all, with a three-month break in between. Two groups of participants for each diet were tested: one that received a standard calorie total for their age and activity level, and another with excess calories.

Both kinds of diets had the same amounts of protein, fat and carbohydrates between the non-processed and ultra-processed versions, but the results were very different. Even when calories were matched, the men gained significantly more weight eating the ultra-processed diets, and their cholesterol levels worsened.

“One of the most shocking findings was this difference in weight status,” said lead author Jessica Preston in a Thursday interview with CTVNews.ca.

“In the calorie-matched (tests), I wasn’t expecting them to have this over-one-kilo difference in weight.”

Preston says the difference may be explained by how the foods interact with the digestive system. Even with a mathematically equal calorie count, numerous factors from fibre and nutrient content, to how foods impact your metabolism over time, could affect how energy is ingested and stored, and how much energy it costs the body to do so.

“Even though you have the same amount that’s going in and out, it might not be going through your biological system in the same way,” she said.

The researchers also found that even an unprocessed diet caused a short-term increase in inflammation, which they believe may have been the body reacting to a sudden change in eating habits.

They say the results suggest that even a short break from ultra-processed food could benefit heart health, metabolism and fertility, especially for people who rely on these foods every day.

Food and fertility

In addition to body weight, subjects eating the highly processed diet were found to have worse sperm quality and motility, as well as lower reproductive hormones like testosterone.

Preston notes that this kind of research can help inform dietary decisions for men interested in becoming fathers; an area of reproductive health advice that has historically been in short supply.

“I think there’s generally been this dogma that men don’t care, and they don’t want to change their lifestyle or their diet, or that there’s nothing that they can do to improve it,” she told CTVNews.ca.

“Men should feel empowered to take action over making healthy lifestyle choices, and that this actually can improve their fertility status.”

While she says the study’s findings are in line with broader epidemiological data on ultra-processed foods, she cautions against jumping to conclusions based on a single piece of research – or on drastically changing your diet, for that matter.

“I would never tell someone to eliminate them from their diet in entirety,” she said. “I tried to do it for a week; it was practically impossible, even though I made people, basically, do it for three weeks.”

What the study does, though, is contribute to the broader understanding that whether a food is ultra-processed is “a good factor to take into consideration,” when making decisions about your diet.

“If you do have an option to have a less-processed or non-ultra-processed alternative, that is usually going to be the better choice,” she said.