It’s advertised as a health food and enjoyed by millions all over the world. 

But a top doctor is warning that yogurt – even if plain and stripped of flavoring – can be processed with chemicals and manmade ingredients which could lead to a range of health problems, including colon cancer.

Dr William Li, whose book Eat to Beat Your Diet is a New York Times bestseller, says that the worst offending yogurts are actually the low-fat varieties, as they are often riddled with chemicals to replicate the thicker and fattier texture.   

The health expert explains: ‘How do you go from processed whole yogurt to ultra processed? You remove the fat. 

‘A lot of people don’t know this because what happens when you remove the fat from yogurt, the whole thing collapses… it doesn’t have a mouth feel.

‘So you know what the manufacturers do? They put additives [and] emulsifiers [in the yogurt] to build back that thick mouth feel of rich yogurt.’

Dr Li’s concerns are mostly theoretical – there is little direct evidence showing yoghurt causes cancer and some actually show it may reduce the risk. 

Yet the health expert points to the use of thickening agents such as carrageenan as concerning. 

Dr William Li, whose book Eat to Beat Your Diet is a New York Times bestseller, says that the worst offending yogurts are actually the low-fat varieties

The ingreident also used in other processed dairy products including creamers, chocolate milk, ice cream, cottage cheese, and sour cream.

While it originates naturally from seaweed, the version used in food manufacturing is heavily processed, making it essentially a synthetic ingredient.

Dr Li reveals that it has recently come to light that manmade carrageenan can cause gut inflammation, which is a significant risk factor for developing colon cancer.

Another thickening agent that the dietician warns about is polysorbate 80. 

A 2021 study from researchers at the University of Paris that fed mice emulsifiers like polysorbate 80 found consuming the products regularly led to increased gut inflammation.

Chronic inflammation can increase the risk for cancer by damaging DNA. 

This, they suggested, could put the body at greater risk for developing colorectal cancers.

A different study in 2021 found introducing emulsifiers to a colony of bacteria that mimicked the kind found in the human gut caused some of the bacteria to die off or become unhealthy.

Research has suggested the bacteria in the gastrointestinal tract play an important role in fighting back against cancer – and that disrupting it could make colorectal cancers more likely.

In 2024 University of Miami Gastroenterologist Dr Maria Abreu, who studies the affect of food additives and their link to colon cancer, likewise said that the affect of emulsifiers on the microbiome could be contributing to the number of young people getting cancer.

Separate 2022 research from the French Nutrition and Cancer Research Network studied more than 102,000 adults and estimated their exposure to different food additives over a day by asking them about their diet habits.

They then tracked them over ten years, and found that those who were estimated to consume higher amounts of certain emulsifiers were more likely to develop breast cancer.

In light of these findings, Dr Li highlights the importance of checking the ingredients before purchasing a product. 

He highlights that full-fat dairy goods are usually free of thickening agents and better for your health that low-fat alternatives. 

He also says plain dairy goods are traditionally better than flavored products, as they tend to contain chemicals and more sugar. 

‘Whole Greek yogurt is processed [but] the moment you add that layer of blueberry jam or whatever… ultra-sweetened stuff, added sugar stuff, now it’s ultra-processed.’

While Dr Li warns of yogurt’s hidden dangers, other experts praise it as a superfood and say that it can actually safeguard against cancer.

Earlier this year, doctors from Harvard University found that people who eat at least two servings of yogurt a week could lower their risk of colon cancers caused by bacteria by 20 per cent.

The researchers looked at colon cancer tumors caused by Bifidobacterium, a type of bacteria that normally helps digest fiber and ward off infections.

However, excess levels can lead to inflammation in the colon, which damages cells and causes them to grow out of control, resulting in cancer.

The researchers believe healthy bacteria, including Bifidobacterium, found in fermented foods like yogurt can reduce the amount of harmful bacteria living in the gut, reducing the risk of bacteria-fueled colon cancers.

Dr Li says one of the worst offending thickening agents is carrageenan, which is also used in other processed dairy products including creamers, chocolate milk, ice cream, cottage cheese, and sour cream

However, they found no link between yogurt and reduced risk of colon cancers caused by other factors such as genes, obesity and chemical exposure.

But Dr Li’s focus it more on yogurts that have been ultra-processed as opposed to chemical-free yogurts.  

It is estimated that more than 70 percent of calories consumed by children and adolescents in the US come from ultra-processed foods. 

This compares to around 30 percent three decades ago.  

A CDC study states that ultra-processed foods are ‘formulations of macronutrients (starches, sugars, fats, and protein isolates) with little, if any, whole food and often with added flavors, colors, emulsifiers, and other cosmetic additives’. 

Examples of ultra-processed foods given include soft drinks, packaged salty snacks, cookies and cakes, processed meats, chicken nuggets, and powdered and packaged instant soups. 

But they can also include some healthier options such as wholegrain breakfast cereals, wholemeal bread, canned beans and tofu, which are softer and more palatable compared to pure ingredients. 

Ultra-processed foods are typically energy-dense products, high in calories, added sugar, unhealthy fats, and salt, and low in dietary fiber, protein, vitamins, and minerals. 

The level of consumption is generally high in high-income countries where the products are more accessible but it is increasing in low-and middle-income countries. 

Research has shown that high intake of ultra-processed foods is associated with a range of health problems including obesity, hypertension, type 2 diabetes, cancer, and cardiovascular disease.