An extra glass of milk may protect against bowel cancer

Taken from Trouw – Elleke Bal – 18 January 2025

British researchers conducted the largest study ever into possible links between diet and the development of bowel cancer.

Not a day goes by without a study on nutrition and health being published. But it is not often that researchers track the eating habits of more than half a million women for sixteen years. This resulted in the largest study ever conducted on the link between bowel cancer and diet, carried out at the University of Oxford.

The diagnosis of bowel cancer has become increasingly common worldwide in recent decades, particularly in wealthy, industrialised countries. It is therefore to be expected that the disease is linked to an unhealthy lifestyle.

Scientists have calculated that around 50 per cent of bowel cancer diagnoses could be prevented by eating healthily and exercising more. Being overweight is a major risk factor. But are there also specific foods that increase or decrease the risk?

The scientists from Oxford investigated this thoroughly. They conducted various studies. In the largest study, they looked at the link between bowel cancer and 97 foods and nutrients over a period of sixteen years. The women who took part in the study reported what they ate in questionnaires. Of the 542,778 women who were followed for sixteen years, around 12,000 developed bowel cancer.

Two culprits and one protector

Statistical analyses identified two culprits: alcohol and red and processed meat increase the risk of developing bowel cancer. But there is also a protector: calcium. The researchers found that taking 300 milligrams of calcium daily, equivalent to a large glass of milk, reduces the risk of developing bowel cancer by 17 per cent.

A causal link cannot be established in this study. Nor is it the case that everyone who drinks extra milk individually reduces their risk by 17 per cent. However, the calculated percentages relating to calcium are interesting when you look at the figures on a large scale. Consider this: around 5 per cent of the population develops bowel cancer, 1 in 20. If a hundred women consume an extra 300 milligrams of calcium every day, there may be four cases of bowel cancer in that group instead of five.

Incidentally, dairy products have long been associated with a reduced risk of developing bowel cancer. Ellen Kampman, professor of nutrition and disease at Wageningen University, obtained her PhD on this subject in 1994. Her conclusion at the time was that dairy products reduce the risk. She is enthusiastic about this British study. “I hope that everyone is now convinced of the fact that you should still consume dairy products.”

Kampman also highlights the significance of another study conducted by scientists at Oxford. They looked at women who are lactose intolerant due to a genetic abnormality and cannot tolerate dairy products. These women were found to have an increased risk of developing bowel cancer. “That is a significant finding.”

Cheese does not help

Which dairy products contain sufficient calcium? The British study found a link with milk drinkers. However, this is also related to the British diet, says Kampman, and applies equally to yoghurt.

However, it is important that these dairy products do not contain too much fat. For example, no link was found with cheese, even though it also contains a lot of calcium. Due to the extra fat, it is less wise to get your extra portion of calcium from cheese, says Kampman.

In the Netherlands, the recommended daily intake of calcium is around 1000 to 1200 milligrams. The British study did not look at calcium from supplements. Milk substitutes such as soya milk do not naturally contain calcium, although it is sometimes added.

According to Kampman, calcium is good for the intestines for various reasons. It is good for the intestinal wall and inhibits unwanted cell division. But it is also an important ‘cleaner’, as it can bind to toxic or unhealthy substances that need to be transported out of the body, such as bile acids and free fatty acids. “It is no coincidence that bowel cancer is linked to food,” says Kampman, “the bowel is where it all ends up.”.

This study by Keren Papier and colleagues, has been published in a scientific journal Nature Communications.