I have a friend who recovered from potentially lethal cancer by relying entirely on changes in diet and lifestyle, including (among other therapies) a strict pescatarian diet, veggie juicing and the elimination of milk products. He was adamant about the importance of eliminating milk products. Normally I’m skeptical since there are more diet fads than great ideas, but my friend had done a lot of hard research, his life being at stake and all. So I figured it was worth asking whether milk really did exacerbate cancer. As it turns out, milk is something of a paradox. Hormones in milk fat, particularly Insulin Growth Factor (IGF) exacerbate certain hormonal cancers. They also seem to increase levels of growth hormone (GH) and thus make kids grow taller. Many Chinese seem eager to incorporate cow’s milk into their diet, despite a long history of not drinking the stuff, because they want taller kids.
Despite the problems posed by hormones in milk, the whey in milk seems to have an anti-cancer effect, especially if it is hydrolyzed (pre-digested.) The reason for this is still unclear, but some have suggested that the high levels of the amino acid cystine, which is used by the body to make glutathione, is responsible. Glutathione is a powerful antioxidant made by the body and there’s an abiding interest in finding ways to increase the amount the body produces.
In any case, because many hormones including IGF are fat-soluable skim milk has most of the hormones removed, along with the fat. This may help explain why skim milk seems to have an anti-cancer effect even when whole milk and other milk products are harmful for those fighting cancer. (Other things to consider include vitamin D3 levels in milk and the calcium content, both of which are relevant to cancer progression and related to one another.)
The role of IGFs in cancer is supported by epidemiologic studies, which have found that high levels of circulating IGF-I and low levels of IGFBP-3 are associated with increased risk of several common cancers, including those of the prostate, breast, colorectum, and lung. source
The current evidence suggests that milk consumption may increase the circulating IGF-I level.
RESULTS: After a month of drinking whole milk, Mongolian children had higher mean plasma levels of IGF-I … and 75th percentile of GH levels (p = 0.005). After a week of drinking low fat milk, Boston girls had small and non-significant increases in IGF-1, IGF-1/IGFBP-3 and GH. CONCLUSION: Milk drinking may cause increases in somatotropic hormone levels of prepubertal girls and boys. The finding that milk intake may raise GH levels is novel, and suggests that nutrients or bioactive factors in milk may stimulate endogenous GH production.
RESULTS: Overall, there was a moderate but statistically non-significant inverse association between intake of low-fat milk or calcium from dairy food and colorectal cancer risk.
Animal models, usually for colon and mammary tumorigenesis, nearly always show that whey protein is superior to other dietary proteins for suppression of tumour development. This benefit is attributed to its high content of cystine/cysteine and gamma-glutamylcyst(e)ine dipeptides, which are efficient substrates for the synthesis of glutathione.