Information sheet: Dairy foods and cancer

Key messages and recommendations

• There is strong evidence the consumption of dairy products (milk, cheese and yoghurt) probably protects against bowel cancer.
• There is strong evidence that calcium supplements probably protect against bowel cancer.
• Cancer Council recommends:
  • Consuming 2-3 serves of milk, yoghurt, cheese and/or their alternatives, mostly reduced fat, each day as recommended by the Australian Dietary Guidelines.
  • There are no specific intake recommendations for dairy products for cancer prevention.

Background

Dairy foods, such as milk, yoghurt and cheese, are a good source of many important nutrients, including protein, calcium, iodine, vitamin A, vitamin D, riboflavin, vitamin B12 and zinc.^[1] Milk and milk-based foods are the richest sources of calcium in the Australian diet and provide calcium in a readily absorbable and convenient form. Calcium is also found in other foods such as almonds and sardines, however in smaller amounts.^[1]

Calcium is the most abundant mineral in the body and is the major mineral constituent of bones. Calcium is required for the growth and maintenance of bones and teeth, as well as proper functioning of the muscular and cardiovascular systems. Calcium metabolism and absorption are controlled by factors such as Vitamin D, parathyroid hormone and hormonal compounds formed by the liver and kidney.^[1]

Biological mechanism

There is strong evidence the consumption of dairy products (milk, cheese and yoghurt) probably protects against bowel cancer. ^[1] The association between the intake of dairy products and decreased risk of bowel cancer development has been largely attributed to their high calcium content. In addition to calcium, lactic acid producing bacteria may also protect against bowel cancer while the casein and lactose in milk may increase calcium bioavailability. Other nutrients or bioactive constituents in dairy products such as lactoferrin, Vitamin D (from fortified dairy products) or the short chain fatty acid butyrate may also impart some protective functions against bowel cancer.^[1]

A long-standing mechanism proposed for calcium and its potential activity against bowel cancer development is the ability of calcium to bind unconjugated bile acids and free fatty acids, reducing their toxic effects on the bowel. More recent cell culture studies suggest that it may also reduce cancer cell proliferation and promote cell differentiation, likely by influencing different cell-signalling pathways.^[1]

Epidemiological evidence

A comprehensive 2018 review of the evidence conducted by the World Cancer Research Fund (WCRF) concluded that there is strong evidence the consumption of dairy products probably protects against bowel cancer.^[1] The evidence for dairy products and bowel cancer includes total dairy, milk and cheese and dietary calcium intakes. Most of the epidemiological studies reviewed in the 3rd expert report are from countries with high intakes of dairy products.

There is limited suggestive evidence that consumption of dairy products decreases the risk of premenopausal breast cancer and there is also limited suggestive evidence that diets high in calcium decrease the risk of pre- and post-menopausal breast cancer. There is limited suggestive evidence that consumption of dairy products and diets high in calcium increase the risk of prostate cancer.

The evidence falls below the threshold for making recommendations regarding dairy products and cancers of the breast and prostate.^[1]

Current consumption levels

The 2011 – 2012 Australian Health Survey showed that over half of the Australian population aged two years and over had inadequate usual intakes of calcium.^[2] However, the prevalence of inadequate calcium intakes was higher amongst females than males, with almost three in four (73%) not meeting their calcium requirements compared with one in two males (51%).^[2] Apart from children aged 2–3, a high proportion of people in each age group have intakes of calcium below the estimated average requirement. For females aged 14–18, 51–70 and 71 and over, this reaches more than 90%.^[3]

In 2011-12, Australians aged two years and over consumed an average 1.5 serves of dairy and/or alternatives per day, with children aged 2-3 years being the highest consumers (1.9 serves per day) and people aged 71 years and over consuming the least with an average 1.2 serves per day.^[4]

Milk is the most commonly consumed dairy food, followed by cheese and yoghurt.^[4]

The low intake of calcium for most age groups is of concern—particularly for older men and women, as low dairy intake has been associated with lower bone mineral density and a higher risk of osteoporosis and fractures, as well as a higher likelihood of being overweight.^[3]

Dietary recommendations

The Australian Dietary Guidelines recommend milk, yoghurt, cheese and /or their alternatives should be eaten every day, mostly as reduced fat versions. Most people need at least 2-3 serves each day, however, the minimum amount recommended varies according to age, sex and life stage, for example, women over 51 years need 4 serves a day as their calcium requirements are high.^[5]