Longevity Briefs: More Reasons To Avoid Ultra-Processed Foods

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem: Unless you picked it directly off a tree, all of the food you eat has been processed in some way. Processing is essentially anything done to food after it has been harvested. Cutting/mashing/grinding it up, adding additives, removing parts of the food or even just putting it in a plastic crate for transportation can be considered processing. Ultra-processed food is made by combining many different ingredients and additives like emulsifiers and thickeners, with little to no whole food at all, to create a ‘food-like substance’ never before seen by the human digestive system.

For reasons we don’t fully understand, these ultra-processed foods seem to be even less healthy than the sum of their parts. In addition to being full of sugar and fat, there seems to be something about heavy food processing that’s just inherently bad for us. Many meta-analyses have found consumption of ultra-processed foods to be correlated with higher mortality. Until now, however, no-one has made a comprehensive analysis of all this evidence. A recent study published in the British Medical Journal (BMJ) has now addressed this by reviewing 45 existing meta-analyses conducted since 2009, including a total of nearly 10 million participants.

The discovery: The review found that across studies that compared high vs low ultra-processed food consumption, people consuming the high levels of ultra-processed foods had an overall 21% increased mortality rate from all causes when compared to those eating low levels of ultra-processed foods. For cardiovascular mortality, this figure was 50%. Ultra processed food consumption was also significantly associated with an increased risk for the majority of the health outcomes investigated in the study. For example, the highest levels of consumption were associated with a 55% increase in obesity risk and a 40% increase in type II diabetes mellitus risk.

In studies that looked at increments of ultra-processed food consumption (such as servings per day), there was a significant dose-response relationship with all cause-mortality and many health conditions – in other words, the more ultra processed foods you eat, the higher your risk.

The study also had a rather unexpected finding: a lack of a significant relationship between ultra-processed food consumption and cancer mortality. This goes against what a lot of previous studies have suggested, with the World Health Organisation even listing ultra-processed meat as carcinogenic.

The implications: This study offers yet more evidence that ultra-processed foods should be avoided. There are many confounding factors that could make these foods look worse than they are – for example, people with less income and lower levels of education are more likely to consume higher levels of ultra processed foods. However, studies try to control for this, and residual confounders are unlikely to fully explain the associations that have been repeatedly shown. There are many interesting theories as to why ultra-processed foods lead to negative health outcomes, some of which are summarised in this article. There’s even research to suggest that when people eat ultra-processed foods, they eat more and gain more weight than people eating whole foods, even when those foods have exactly the same nutrient composition.

While this study didn’t find a significant relationship between ultra-processed foods and cancer, it’s important to note that they didn’t sub-analyse different types of processed foods. Ultra-processed meat, for example, may still be associated with cancer, but this association could have been lost in the data for other ultra-processed foods for which the association is less strong. Besides, who is worried about cancer but perfectly fine with heart disease and diabetes?