UPFs and fertility

There has been an explosion in the consumption of ultra-processed food or UPFs in recent years and it’s estimated that over 50% of the food bought in the UK now consists of UPF. Compare this with 14.2% and 13.4% for our French and Italian neighbours respectively.

In a large-scale review involving almost 10 million people around the world, UPF has been linked to 32 harmful effects to our health, including high risk of heart disease, cancer, type 2 diabetes and early mortality. While this particular review did not examine the impact of high consumption of ultra-processed foods on fertility, there is an increasing body of research into this field.

What are ultra-processed foods?

“Our consumption is so high because so much of our diet come under the banner of being a processed food in the first place,” explains dietitian Alex Ballard. “Often, we think that this just means crisps, sweets or ready meals and, while it is true that many ultra-processed foods are high in unhealthy fats, sugar, and salt, not all are ‘unhealthy’.

“So, things like fortified breakfast cereal, such as Weetabix or Shredded Wheat, wholegrain bread, low fat yogurts, hummus can be classified as processed foods yet still be part of a healthy diet.”

Indeed, there is no single, universally agreed definition for ultra-processed foods. The term itself originates from the NOVA classification system, which was created by scientists at the University of São Paulo in Brazil.

NOVA divides foods into four main categories according to how much industrial processing they undergo.

• Unprocessed or minimally processed foods: These are natural foods like fruit, vegetables, milk, fish, pulses, eggs, nuts, and seeds that have had minimal or no alteration and no added ingredients.
• Processed culinary ingredients: These include substances used in cooking rather than eaten alone, such as oil, sugar, and salt.
• Processed foods: Made by blending ingredients from the first two groups, these are foods that could feasibly be prepared at home and examples include jams, pickles, canned fruits or vegetables, cheeses, and freshly baked breads.
• Ultra-processed foods: These contain multiple industrial ingredients and additives rarely used domestically. They often feature preservatives, emulsifiers, sweeteners, and artificial colours or flavours, to give them a long shelf life.

What impact does ultra-processed food have on fertility?

Emerging evidence indicates that consuming large amounts of ultra-processed foods may adversely affect fertility in both women and men although the lack of a universal definition of what a UPF is contributes to the confusion of what we should and shouldn’t be eating.

“Although we have studies that show high consumption of these foods can produce poorer health outcomes and affect things like fertility, one research study will be testing certain foods, and another research study will test completely different foods.

“When it comes to fertility, researchers have examined the impact on both men and women, and several mechanisms are believed to play a role.”

Increased inflammation and oxidative stress

Ultra-processed foods are typically high in sugars, unhealthy fats, and artificial ingredients, all of which can trigger inflammation and oxidative damage in the body. Such effects may interfere with reproductive function by disturbing hormone regulation. In men, oxidative stress can attack sperm membranes and fragment DNA, which is linked to lower sperm motility and higher miscarriage risk.

Hormonal disturbances

Diets rich in highly processed products can disrupt hormone balance by impacting the endocrine system. For instance, spikes in insulin levels from processed sugars may impair reproductive hormones, potentially disrupting ovulation in women and reducing sperm production in men.

Depriving the body of essential nutrients

These foods often provide minimal vitamins, minerals, and antioxidants. The resulting nutrient deficiencies can affect fertility by lowering the quality of eggs and sperm.

Weight gain and metabolic problem

Frequent consumption of ultra-processed items is linked to obesity and other metabolic issues. Conditions like obesity and metabolic dysfunction are known contributors to infertility, such as polycystic ovary syndrome (PCOS) in women or diminished sperm quality in men.

In a 2025 study, healthy young men were placed on two tightly controlled diets, one high in UPFs and one composed of unprocessed foods, while ensuring that calorie intake was the same. It found that men gained fat mass on the UPF diet despite eating the same calories. As LDL cholesterol levels rose, there was a notable decrease in follicle‑stimulating hormone (FSH), a key driver of sperm production.

A fertility dietitian’s advice on UPFs

An NHS dietitian for ten years, Alex’s keen interest in female health and understanding of how diet can improve conditions such as PCOS and endometriosis led her to specialise in fertility nutrition.

“I believe we should approach UPFs in a nuanced way rather than demonising everything that falls under the banner of being processed. We should always ask ourselves, does this seem healthy? Is it nutrient dense? Does it have lots of vitamins and minerals? Is it high in fibre?

“If you’re answering yes, then then they’re going to be good things to include. Even the foods that do not have a lot of nutritional value can still have a place. Typicallly, they taste good and absolutely we can have food just for enjoyment’s sake. However, if we are having them in large quantities on a regular basis over a long period of time, then they are likely to have a detrimental impact on our health.

“I think it’s also important to highlight that sometimes we hear the word additives, and we think that’s a negative, whereas it can mean nutrient fortification, including added calcium vitamin D, or iodine, and that’s a positive. Or it could be quite a natural ingredient that is making the food safer to consume, increasing the shelf life, or making it more affordable so it’s accessible for more people.”

Alex’s tips on navigating UPFs:

• Try to be organised with food planning and prep so you don’t reach for convenience foods which are likely to be ultra processed.
• Take a packed lunch into work or take snacks out with you when you’re on the go.
• Try to cook meals from scratch if you can as you’re likely to use ingredients in their naturally occurring form.
• You don’t have to abstain completely but look at your consumption and try to reduce it down and switch over to natural foods as much as possible.
• Look at the ingredients list on foods you’re considering consuming. As a very general rule, if there is only a small handful of ingredients, most of which you recognise or have a place in the domestic kitchen, then the food is likely to have gone through a minimal amount of processing. Whereas a long list of ingredients that you don’t recognise is a red flag.

For more advice on fertility nutrition, please visit our support hub or arrange a consultation with Alex Ballard.