Growth factors in milk and dairy products: ANSES publishes its opinion on their impact on the risk of developing cancer
Growth factors are substances produced naturally by humans and many animal species. They are thus found in animal products such as milk. These substances are necessary for development and act primarily on cellular growth and proliferation. The Agency received a formal request from the consumer association "Familles de France" to assess the risk associated with growth factors in milk and dairy products, by investigating their contribution to the cancer development process. Following expert appraisal work lasting two years, based on a review of all the available studies, the Agency is unable to demonstrate the impact of growth factors (IGF-1) in milk and dairy products on the risk of developing cancer and concludes that their contribution, if any, appears to be small.
Growth factors are substances produced naturally by humans and many animal species. They play a variety of physiological roles within the body and act primarily on cellular growth, differentiation and metabolism. Several classes of growth factor can be distinguished, according to their role in the body. Insulin-like growth factors (IGF), especially IGF-1, are the most widely studied by the scientific community.
Growth factors are found in all body tissues and fluids (blood, milk, etc.). Given their role in cell proliferation mechanisms, numerous scientific studies have investigated whether these substances, particularly IGF-1, may play a role in the cancer development process.
In September 2009, the Agency received a formal request from the consumer association "Familles de France" to assess the cancer risk associated with growth factors in milk and dairy products. The results of these studies are being published today.
The Agency's work
The analysis of the available scientific data conducted by ANSES shows positive associations in humans between blood levels of IGF-1 and the incidence of certain common cancers (prostate, breast, colorectal). Thus, one question is to determine whether IGF-1 in milk and dairy products may contribute to blood levels of IGF-1 in humans.
In particular, the Agency sought to characterise the levels of growth factors in milk and dairy products and determine whether these growth factors were likely to pass into the blood.
During the manufacturing of products derived from milk, raw milk undergoes many technological changes whose cumulative effects lead to a reduction in growth factor levels (the available data show that IGF-1 is no longer detectable after high-temperature heat treatment, which concerns most of the milk sold for consumption in France). In addition, the growth factors are degraded during the different stages of digestion, and their absorption by the body gradually decreases with age. ANSES therefore considers that if any IGF-1 from milk does join the bloodstream, this quantity is small compared to the circulating quantities of IGF-1 produced naturally by the body.
On this basis, the Agency considers that if there is any contribution by IGF-1 from milk to the cancer risk, it appears to be small.
Moreover, it appears from ANSES's work that other dietary factors such as protein intake and energy intake may have a role in modulating the synthesis of IGF-1 produced by the body itself. This point requires further research.
Lastly, in terms of nutritional prevention of cancer, ANSES reiterates its recommendations, namely: limiting the consumption of alcoholic beverages, favouring a balanced and varied diet, and engaging in physical activity.