I'm not a scientist, much of the research is contradicted by other sources as with all contentious areas, and I don't know the in-depth details of the studies. However from what I have read milk has been linked to:
1. Breast Cancer- both the levels of oestrogen in milk and the hormone insulin-like growth factor-I (IGF-I) present in milk when bovine growth hormone is used has been associated with an increased breast cancer risk (
http://www.thelancet.com/journals/la...384-1/abstract "A positive relation between circulating IGF-I concentration and risk of breast cancer was found among premenopausal but not postmenopausal women.")
http://www.thelancet.com/journals/la...438-1/fulltext
An explanation of these studies:
http://www.purefood.org/rBGH/rach598.htm
Studies also often point to the very low instances of breast cancer in China and Japan and the very high instances in the UK, USA etc. (A figure I have read is one in 10,000 women in China die from breast cancer - 1 in 12 in the UK
http://www.alternative-healthzine.com/html/1200_2.html)
2. Prostate Cancer- IGF-1 again
http://www.sciencemag.org/content/279/5350/563.abstract
3. Ovarian cancer- eating four portions of milk products a day doubles the risk compared to those who eat two (there doesn't seem to be any data on those who eat none)
http://www.sciencedaily.com/releases...0805064340.htm
http://www.ncbi.nlm.nih.gov/pubmed/16052536
http://www.webmd.com/ovarian-cancer/...ovarian-cancer
4. Osteoporosis- dairy has an acid effect on the body (along with meat (including fish), eggs, tea, coffee and fizzy drinks) whereas fruit and veg have an alkalinic effect. The importance of this is that: "Like all animal protein, milk acidifies the body pH which in turn triggers a biological correction. You see, calcium is an excellent acid neutralizer and the biggest storage of calcium in the body is - you guessed it… in the bones. So the very same calcium that our bones need to stay strong is utilized to neutralize the acidifying effect of milk. Once calcium is pulled out of the bones, it leaves the body via the urine, so that the surprising net result after this is an actual calcium deficit."
http://saveourbones.com/osteoporosis-milk-myth/
Too much calcium can also be an issue
http://www.4.waisays.com/ExcessiveCalcium.htm
Again there are lower levels of osteoporosis in cultures that do not use high levels of dairy, compared to those that do.
http://milk.elehost.com/html/osteoporosis.html
5. Diabetes- milk has been found to increase insulin resistance-
http://www.nature.com/ejcn/journal/v.../1602086a.html
6. High Cholestrol/ Heart Disease- Due to high levels of saturated fat, and the milk protein casein A1 has been linked to heart disease.
http://news.bbc.co.uk/1/hi/health/1268481.stm
7. B12 deficiency (goats milk only)- goats milk has been found to contain a substance which binds with B12 and can cause a deficiency
8. Acne-
http://acne.about.com/od/acnetriggers/a/milkandacne.htm
http://www.acnemilk.com/the_no_milk_acne_diet
And that's not to mention that clearly there's people with lactose intolerance, and there are also dairy links to allergies, asthma, sinus issues, mood swings and depression.
There is a lot of evidence out there on either side of the 'milk- health food or poison for humans' debate but I feel that based particularly on the fact that many of these conditions rarely occur in cultures where dairy is not consumed, there must be some truth that milk can cause significant problems to the human body, plus it is unnatural to drink as an adult and from another species, plus it is a cruel industry resulting in a lot of suffering and death... now that it's no longer in my diet I feel well rid of it.