Milk Consumption and Calcium: A Possible Shield Against Cancer?

In 2022, cancer in its various forms remained a leading cause of death in the developed world, constituting the leading cause of death in Canada, the second leading cause in the United States, and nearly equal to heart disease in the United Kingdom. Breast cancer in women and prostate cancer in men remained the most frequently diagnosed, followed by lung and colorectal cancers in both sexes. Studies show that colon cancer rates among immigrants change within just over ten years after moving, approaching those of the country they migrated to. This pattern suggests that lifestyle and environmental conditions are closely linked to the development of the disease.

Among the main environmental factors associated with cancer is diet, particularly in organs like the colon, which is part of the digestive system. However, as of now, there is no consensus among scientists regarding the link between most dietary factors and the risk of colon cancer. Alcohol and processed meat are the only food items with consistent findings indicating their association with the disease, while other components have been studied much less. There is a particular lack of studies examining all types of food together, and even in the existing research, measurement errors or small participant numbers are common limitations.

Alcohol and Calcium

A recent study, published in Nature Communications, sought to address gaps in existing research by systematically analyzing 97 nutritional components and examining their relationship to colon cancer risk. The data was taken from an ongoing UK cohort study that followed 542,778 women for an average of 16.6 years. At the study’s outset, participants completed a detailed nutritional questionnaire. Over the follow-up period, 12,251 women were diagnosed with colon cancer. The risk of developing the disease was found to increase with age and physical height, and was higher in women with a family history of colon cancer as well as those who reported less healthy lifestyle habits compared to the other participants in the cohort.

Of the 97 nutritional components analyzed in the study, 17 were found to have a significant association with colon cancer risk, with the most prominent being alcohol and calcium. Alcohol consumption was strongly linked to an increased risk: for every additional 20 grams consumed per day, the risk rose by 15%. In contrast, consumption of calcium-rich foods, such as milk and dairy products, was associated with a reduced risk of colon cancer—every additional 300 mg per day lowered the risk by 17%. Other dairy components, however, showed no meaningful relationship to colon cancer risk.

Even after accounting for factors such as smoking, physical activity, and body mass index, the associations between alcohol, calcium, milk, and colon cancer remained consistent. While the findings cannot prove a cause-and-effect relationship between specific dietary components and the development of the disease, the fact that cross-referencing with other food components did not change the results suggests a potential direct influence of these nutrients on cancer risk.

On the other hand, while an initial negative correlation was observed between fruit and grain consumption and colon cancer risk, this association weakened after adjusting for other factors. This suggests that this relationship may be partly attributable to a broader pattern of a healthy lifestyle—particularly the adoption of a diverse, nutrient-rich diet centered on fresh, plant-based foods.

Genetic Predisposition to Milk Consumption

To further support their findings, the researchers examined participants’ genetic predisposition to milk consumption. The ability to digest lactose—the sugar in milk—beyond infancy is associated with well-known genetic variants.  Individuals with these gene variants can break down lactose without experiencing digestive discomfort and therefore tend to consume more milk. This genetic trait provides an objective indicator of milk intake, minimizing the biases and inaccuracies often associated with self-reported dietary data. 

The study found that the protective effect of milk against colon cancer was stronger when milk consumption was estimated based on genetic predisposition, and weaker when relying solely on participants’ self-reported intake. If milk consumption does indeed offer protection against colon cancer, this suggests that individuals with lactose intolerance may need to seek alternative dietary sources of calcium, as calcium appears to be the key protective component.

These findings are consistent with previous research and recommendations from health organizations such as the World Cancer Research Fund (WCRF), which has shown a dose-dependent relationship between alcohol consumption and increased colon cancer risk. Likewise, similar to the current study, other research has found that even one daily glass of milk is significantly associated with a statistically meaningful reduction in the risk of developing colon cancer.