How does processed food affect our health?

Unprocessed, or whole food, is as close to its naturally occurring state as possible. It is usually a single ingredient and nutritious and has not been processed by adding fat and sugar and removing its nutrients. Foods that are cut, dried or cooked, but nothing much is added or removed from them are minimally processed. Ultra-processed foods have chemical substances extracted or refined from whole foods such as hydrogenated oils, high-fructose corn syrup, flavouring agents and emulsifiers. Ultra-processed products are typically low in dietary fibre, micronutrients and phytochemicals. They are often cheaper and more convenient than making a meal from whole foods but they are usually high in calories, salt, sugar and fat. Over half of the food bought in the UK is ultra-processed.


Effect of Ultra-processed food on health

Although ultra-processed foods are convenient, studies indicate they increase the risk of health problems. One study in 100,000 adults, found that eating 10% more ultra-processed foods, such as ready meals, sugary cereals and salty snacks, was associated with a 10-12% increase in the risks of heart disease, strokes and cancer. Another large study found that eating more than 4 servings of processed food a day was associated with an increased risk of death. For each additional serving, mortality risk increased by 18%.


Processed food and health

Processed food and health

What about the effects of ultra-processed foods on the gut microbiome and weight?

The microbiome is a diverse ecosystem of trillions of bacteria of about 1000 different species living in our gut. Everyone’s gut microbiota is unique but there are certain combinations and collections of bacteria that are found in healthy individuals. Gut microbiota plays many roles. It metabolises nutrients from food and certain medications, serves as a protective barrier against intestinal infections, and produces vitamin K, which helps make blood-clotting proteins. However, preliminary research findings suggest gut bacteria may be the key to preventing or treating some diseases. What we eat will influence the makeup of our gut microbiome.

Emulsifiers are added to most processed foods to help texture and extend shelf life and have been found to alter the gut microbiota composition in mice. To study how emulsifiers were affecting gut bacteria, scientists at Georgia State University added emulsifiers in varying concentrations to the drinking water of lab mice. They were all fed the same diet – the only difference was the amount of emulsifiers they were consuming.

The researchers found that mice that had been fed the emulsifiers overate, became obese and developed problems such as high blood sugar and fatty liver. In addition, they had less microbial diversity in their colons than mice who had not been given emulsifiers. It appears that in mice, consuming emulsifiers may contribute to obesity by causing an imbalance in the gut microbial ecosystem.



There are no long-term studies on the effects of emulsifiers or other food additives in humans. However, a randomised controlled trial published last year looked at the impact of eating ultra-processed foods on weight in humans. The researchers led by Dr. Kevin D. Hall compared body weight changes and calorie consumption for 20 healthy adults who ate either an ultra-processed or a minimally processed diet for two weeks. Each spent two weeks on both of the diets. The ultra-processed and minimally processed meals had the same number of calories, sugars, fibre, fat and carbohydrates. Participants could eat as much or as little as they wanted.

On the ultra-processed diet, people ate about 500 calories more per day than they did on the minimally processed diet. People also ate faster on the ultra-processed diet and gained an average of 1kg. When they were on the minimally processed diet, they lost about the same amount of weight.



The healthiest foods that we can eat are foods that are the least processed. The populations with low meat, high fibre, and minimally processed foods have far less chronic diseases, obesity rates and live longer disease-free. Base your diet on fresh fruit and vegetables, nuts and legumes, fish and whole grain. Try to minimise your intake of ultra-processed foods. As a rule of thumb the longer the ingredient list, the more chemical products in the list, the more likely the food is highly processed.


By Dr Mohgah Elsheikh