Health Concerns about Dairy Products
Many Americans, including some vegetarians, still consume substantial amounts of dairy products—and government policies still promote them—despite scientific evidence that questions their health benefits and indicates their potential health risks.
Calcium is an important mineral that helps to keep bones strong. Our bones are constantly remodelling, meaning the body takes small amounts of calcium from the bones and replaces it with new calcium. Therefore, it is essential to have enough calcium so that the body doesn’t decrease bone density in this remodelling process. Though calcium is necessary for ensuring bone health, the actual benefits of calcium intake do not exist after consumption passes a certain threshold. Consuming more than approximately 600 milligrams per day—easily achieved without dairy products or calcium supplements—does not improve bone integrity.1
Clinical research shows that dairy products have little or no benefit for bones.
A 2005 review published in Paediatrics showed that milk consumption does not improve bone integrity in children.2 In a more recent study, researchers tracked the diets, physical activity, and stress fracture incidences of adolescent girls for seven years, and concluded that dairy products and calcium do not prevent stress fractures in adolescent girls.3 Similarly, the Harvard Nurses’ Health Study, which followed more than 72,000 women for 18 years, showed no protective effect of increased milk consumption on fracture risk.1
It is possible to decrease the risk of osteoporosis by reducing sodium intake in the diet,4,5 increasing intake of fruits and vegetables,5,6 and ensuring adequate calcium intake from plant foods such as kale, broccoli, and other leafy green vegetables and beans. You can also use calcium-fortified products such as breakfast cereals and juices. Soy milk and fortified orange juice are two examples of products which provide about the same amount of calcium per serving as milk or other dairy products.7
Exercise is one of the most effective ways to increase bone density and decrease the risk of osteoporosis,8,9 and its benefits have been observed in studies of both children and adults.8,10-11
Individuals often drink milk in order to obtain vitamin D in their diets, unaware that they can receive vitamin D through other sources. Without vitamin D, only 10-15 percent of dietary calcium is absorbed.12
The best natural source of vitamin D is sunlight. Five to 15 minutes of sun exposure to the arms and legs or the hands, face, and arms can be enough to meet the body’s requirements for vitamin D, depending on the individual’s skin tone.13 Darker skin requires longer exposure to the sun in order to obtain adequate levels of vitamin D. In colder climates during the winter months the sun may not be able to provide adequate vitamin D. During this time the diet must be able to provide vitamin D.
Few foods naturally contain vitamin D, and no dairy products naturally contain this vitamin. Therefore, fortified cereals, grains, bread, orange juice, and soy or rice milk exist as options for providing vitamin D through the diet.14 Supplements are also available.
Fat Content and Cardiovascular Disease
Dairy products—including cheese, ice cream, milk, butter, and yogurt—contribute significant amounts of cholesterol and saturated fat to the diet.15 Diets high in fat and especially in saturated fat can increase the risk of heart disease and can cause other serious health problems.
A low-fat, plant-based diet that eliminates dairy products, in combination with exercise, smoking cessation, and stress management, can not only prevent heart disease, but may also reverse it.16,17
Dairy and Cancer
Consumption of dairy products has also been linked to higher risk for various cancers, especially to cancers of the reproductive system. Most significantly, dairy product consumption has been linked to increased risk for prostate18-20 and breast cancers.21
The danger of dairy product consumption as it relates to prostate and breast cancers is most likely related to increases in insulin-like growth factor (IGF-1), which is found in cow’s milk.22 Consumption of milk and dairy products on a regular basis has been shown to increase circulating levels of IGF-1.23,24 Perhaps the most convincing association between IGF-1 levels and cancer risk is seen in studies of prostate cancer. Case-control studies in diverse populations have shown a strong and consistent association between serum IGF-1 concentrations and prostate cancer risk.25 One study showed that men with the highest levels of IGF-1 had more than four times the risk of prostate cancer, compared with those who had the lowest levels.26 In the Physicians Health Study, tracking 21,660 participants for 28 years, researchers found an increased risk of prostate cancer for those who consumed ≥2.5 servings of dairy products per day as compared with those who consumed ≤0.5 servings a day.19 This study, which is supported by other findings,27,28 also shows that prostate cancer risk was elevated with increased consumption of low-fat milk, suggesting that too much dairy calcium, and not just the fat associated with dairy products, could be a potential threat to prostate health.
In addition to increased levels of IGF-1, estrogen metabolites are considered risk factors for cancers of the reproductive system, including cancers of the breasts, ovaries, and prostate. These metabolites can affect cellular proliferation such that cells grow rapidly and aberrantly,29 which can lead to cancer growth. Consumption of milk and dairy products contributes to the majority (60-70 percent) of estrogen intake in the human diet.
In a large study including 1,893 women from the Life After Cancer Epidemiology Study who had been diagnosed with early-stage invasive breast cancer, higher amounts of high-fat dairy product consumption were associated with higher mortality rates. As little as 0.5 servings a day increased risk significantly. This is probably due to the fact that estrogenic hormones reside primarily in fat, making the concern most pronounced for consumption of high-fat dairy products.
The consumption of dairy products may also contribute to development of ovarian cancer. The relation between dairy products and ovarian cancer may be caused by the breakdown of the milk sugar lactose into galactose, a sugar which may be toxic to ovarian cells.30 In a study conducted in Sweden, consumption of lactose and dairy products was positively linked to ovarian cancer.31 A similar study, the Iowa Women’s Health Study, found that women who consumed more than one glass of milk per day had a 73 percent greater chance of developing ovarian cancer than women who drank less than one glass per day.32
Lactose intolerance is common among many populations, affecting approximately 95 percent of Asian-Americans, 74 percent of Native Americans, 70 percent of African-Americans, 53 percent of Mexican-Americans, and 15 percent of Caucasians.33 Symptoms, which include gastrointestinal distress, diarrhoea, and flatulence, occur because these individuals do not have the enzyme lactate to digest the milk sugar lactose. When digested, the breakdown products of lactose are two simple sugars: glucose and galactose. Nursing children have active enzymes that break down galactose, but as we age, many of us lose much of this capacity.34 Due to the common nature of this condition, and in order to avoid these uncomfortable side effects, milk consumption is not recommended.
Milk contains contaminants that range from hormones to pesticides. Milk naturally contains hormones and growth factors produced within a cow’s body. In addition, synthetic hormones such as recombinant bovine growth hormone are commonly used in cows to increase the production of milk.35 Once introduced into the human body, these hormones may affect normal hormonal function.
When treating cows for conditions such as mastoiditis, or inflammation, of the mammary glands, antibiotics are used, and traces of these antibiotics have occasionally been found in samples of milk and dairy products. This treatment is used frequently, because mastoiditis is a very common condition in cows, due to dairy product practices which have cows producing more milk than nature intended.
Pesticides, poly chlorinated biphenyls (PCBs), and dioxins are other examples of contaminants found in milk. Dairy products contribute to one-fourth to one-half of the dietary intake of total dioxins.36 All of these toxins do not readily leave the body and can eventually build to harmful levels that may affect the immune, reproductive, and the central nervous systems. Moreover, PCBs and dioxins have also been linked to cancer.37
Other contaminants often introduced during processing of milk products include melamine, often found in plastics, which negatively affects the kidneys and urinary tract due to their high nitrogen content,38 and carcinogenic toxins including aflatoxins. These are additionally dangerous because they are not destroyed in pasteurization.39
Milk Proteins and Diabetes
Insulin-dependent (type 1 or childhood-onset) diabetes is linked to consumption of dairy products in infancy.40 A 2001 Finnish study of 3,000 infants with genetically increased risk for developing diabetes showed that early introduction of cow’s milk increased susceptibility to type 1 diabetes.41 In addition, the American Academy of Paediatrics observed up to a 30 percent reduction in the incidence of type 1 diabetes in infants who avoid exposure to cow’s milk protein for at least the first three months of their lives.42
Health Concerns about Milk for Children and Infants
Milk proteins, milk sugar, fat, and saturated fat in dairy products pose health risks for children and encourage the development of obesity, diabetes, and heart disease. While low-fat milk is often recommended for decreasing obesity risk, a study published in the Archives of Disease in Childhood showed that children who drank 1 percent or skim milk, compared with those who drank full-fat milk, were not any less likely to be obese.43 Moreover, a current meta-analysis found no support for the argument that increasing dairy product intake will decrease body fat and weight over the long term (>1 year).44
For infants, the consumption of cow’s milk is not recommended. The American Academy of Paediatrics recommends that infants below 1 year of age not be given whole cow’s milk,45 as iron deficiency is more likely due to the low amount of iron found in cow’s milk as compared with human breast milk.46 Colic is an additional concern with milk consumption. Up to 28 percent of infants suffer from colic during the first month of life.47 Paediatricians learned long ago that cow’s milk was often the reason. We now know that breastfeeding mothers can have colicky babies if the mothers consume cow’s milk. The cow’s antibodies can pass through the mother’s bloodstream, into her breast milk, and to the baby.48,49
Additionally, food allergies appear to be common results of cow’s milk consumption, particularly in children.50,51 Cow’s milk consumption has also been linked to chronic constipation in children.52
Milk and dairy products are not necessary in the diet and can, in fact, be harmful to health. It is best to consume a healthful diet of grains, fruits, vegetables, legumes, and fortified foods including cereals and juices. These nutrient-dense foods can help you meet your calcium, potassium, riboflavin, and vitamin D requirements with ease—and without facing the health risks associated with dairy product consumption.
1. Feskanich D, Willett WC, Colditz GA. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr. 2003;77:504–511.
2. Lanou AJ, Berkow SE, Barnard ND. Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence. Pediatrics. 2005;115:736–743.
3. Sonneville KR, Gordon CM, Kocher MS, Pierce LM, Ramappa A, Field AE. Vitamin D, calcium, and dairy intakes and stress fractures among female adolescents. Arch Pediatr Adolesc Med. 2012;166:595-600.
4. Reid DM, New SA. Nutritional influences on bone mass. Proceed Nutr Soc. 1997;56:977–987.
5. Lin P, Ginty F, Appel L, et al. The DASH diet and sodium reduction improve markers of bone turnover and calcium metabolism in adults. J Nutr. 2001;133:3130–3136.
6. Tucker KL, Hannan MR, Chen H, Cupples LA, Wilson PWF, Kiel DP. Potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr. 1999;69:727–736.
7. National Institutes of Health. NIH Osteoporosis and Related Bone Diseases National Resource Center. Calcium and Vitamin D: Important at Every Age. Available at: http://www.niams.nih.gov/Health_Info/Bone/Bone_Health/Nutrition/. Accessed September 24, 2013.
8. Prince R, Devine A, Dick I, et al. The effects of calcium supplementation (milk powder or tablets) and exercise on bone mineral density in postmenopausal women. J Bone Miner Res. 1995;10:1068–1075.
9. Going S, Lohman T, Houtkooper L, et al. Effects of exercise on bone mineral density in calcium-replete postmenopausal women with and without hormone replacement therapy. Osteoporos Int. 2003;14:637–643.
10. Lunt M, Masaryk P, Scheidt-Nave C, et al. The effects of lifestyle, dietary dairy intake and diabetes on bone density and vertebral deformity prevalence: the EVOS study. Osteoporos Int. 2001;12:688–698.
11. Lloyd T, Beck TJ, Lin HM, et al. Modifiable determinants of bone status in young women. Bone. 2002;30:416–421.
12. Holick MF, Garabedian M. Vitamin D: photobiology, metabolism, mechanism of action, and clinical applications. In: Favus MJ, ed. Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism. 6th ed. Washington, DC: American Society for Bone and Mineral Research; 2006:129-137.
13. Holick M. The vitamin D epidemic and its health consequences. J Nutr. 2005;135:2739S–2748S.
14. Zhang R, Naughton D. Vitamin D in health and disease: current perspectives. Nutr J. 2010;9:65.
15. Warensjo E, Jansson JH, Berglund L, et al. Estimated intake of milk fat is negatively associated with cardiovascular risk factors and does not increase the risk of a first acute myocardial infarction. Br J Nutr. 2004;91:635–642.
16. Szeto YT, Kwok TC, Benzie IF. Effects of a long-term vegetarian diet on biomarkers of antioxidants status and cardiovascular disease risk. Nutrition. 2004;20:863–866.
17. Ornish D, Brown SE, Scherwitz LW, et al. Can lifestyle changes reverse coronary heart disease? Lancet. 1990;336:129–133.
18. Qin L, Xu J, Wang P, Tong J, Hoshi K. Milk consumption is a risk factor for prostate cancer in Western countries: evidence from cohort studies. Asia Pac J Clin Nutr. 2007;16:467–476.
19. Song Y, Chavarro JE, Cao Y, et al. Whole milk intake is associated with prostate cancer-specific mortality among U.S. male physicians. J Nutr. 2013;143:189-196.
20. Chan JM, Stampfer MJ, Ma J, Gann PH, Gaziano JM, Giovannucci E. Dairy products, calcium, and prostate cancer risk in the Physicians’ Health Study. Am J Clin Nutr. 2001;74:549-554.
21. Kroenke CH, Kwan ML, Sweeney C, Castillo A, Caan Bette J. High-and low-fat dairy intake, recurrence, and mortality after breast cancer diagnosis. J Natl Cancer Inst. 2013;105:616-623.
22. Voskuil DW, Vrieling A, van’t Veer LJ, Kampman E, Rookus MA. The insulin-like growth factor system in cancer prevention: potential of dietary intervention strategies. Cancer Epidemiol Biomarkers Prev. 2005;14:195–203.
23. Cadogan J, Eastell R, Jones N, Barker ME. Milk intake and bone mineral acquisition in adolescent girls: randomised, controlled intervention trial. BMJ. 1997;315:1255–1260.
24. Qin LQ, He K, Xu JY. Milk consumption and circulating insulin-like growth factor-I level: a systematic literature review. Int J Food Sci Nutr. 2009;60:330-340.
25. Cohen P. Serum insulin-like growth factor-I levels and prostate cancer risk—interpreting the evidence. J Natl Cancer Inst. 1998;90:876–879.
26. Chan JM, Stampfer MJ, Giovannucci E, et al. Plasma insulin-like growth factor-1 and prostate cancer risk: a prospective study. Science. 1998;279:563–565.
27. Chan JM, Stampfer MJ, Ma J, Gann PH, Gaziano JM, Giovannucci E. Dairy products, calcium, and prostate cancer risk in the Physicians’ Health Study. Am J Clin Nutr. 2001;74:549–554.
28. Tseng M, Breslow RA, Graubard BI, Ziegler RG. Dairy, calcium and vitamin D intakes and prostate cancer risk in the National Health and Nutrition Examination Epidemiologic Follow-up Study cohort. Am J Clin Nutr. 2005;81:1147–1154.
29. Farlow DW, Xu X, Veenstra TD. Quantitative measurement of endogenous estrogen metabolites, risk-factors for development of breast cancer, in commercial milk products by LC-MS/MS. J Chromatogr B. 2009;877:1327-1334.
30. Cramer DW, Greenberg ER, Titus-Ernstoff L, et al. A case-control study of galactose consumption and metabolism in relation to ovarian cancer. Cancer Epidemiol Biomarkers Prev. 2000;9:95–101.
31. Larsson SC, Bergkvist L, Wolk A. Milk and lactose intakes and ovarian cancer risk in the Swedish Mammography Cohort. Am J Clin Nutr. 2004;80:1353–1357.
32. Kushi LH, Mink PJ, Folsom AR, et al. Prospective study of diet and ovarian cancer. Am J Epidemiol. 1999;149:21–31.
33. Bertron P, Barnard ND, Mills M. Racial bias in federal nutrition policy, part I: the public health implications of variations in lactase persistence. J Natl Med Assoc. 1999;91:151–157.
34. Swallow DM. Genetics of lactase persistence and lactose intolerance. Annu Rev Genet. 2003;37:197–219.
35. Outwater JL, Nicholson A, Barnard N. Dairy products and breast cancer: the IGF- 1, estrogen, and bGH hypothesis. Med Hypothesis. 1997;48:453–461.
36. Bhandari SD, Schmidt RH, Rodrick GE. Hazards resulting from environmental, industrial, and agricultural contaminants. In: Schmidt RH, Rodrick GE, eds. Food Safety Handbook. Hoboken, N.J.: John Wiley & Sons, Inc.; 2005:291–321.
37. Baars AJ, Bakker MI, Baumann RA, et al. Dioxins, dioxin-like PCBs and nondioxin- like PCBs in foodstuffs: occurrence and dietary intake in the Netherlands. Toxicol Lett. 2004;151:51–61.
38. Fischer WJ, Schilter B, Tritscher AM, Stadler RH. Contaminants of milk and dairy products: contamination resulting from farm and dairy practices. In: Fuquay JW, ed. Encyclopedia of Dairy Sciences. 2nd ed. San Diego, CA: Academic Press; 2011:887–897.
39. Prandini A, Tansini G, Sigolo S, Filippi L, Laporta M, Piva G. On the occurrence of aflatoxin M1 in milk and dairy products. Food Chem Toxicol. 2009;47:984–991.
40. Saukkonen T, Virtanen SM, Karppinen M, et al. Significance of cow’s milk protein antibodies as risk factor for childhood IDDM: interaction with dietary cow’s milk intake and HLA-DQB1 genotype. Childhood Diabetes in Finland Study Group. Dibetologia. 1998;41:72–78.
41. Kimpimaki T, Erkkola M, Korhonen S, et al. Short-term exclusive breastfeeding predisposes young children with increased genetic risk of type I diabetes to progressive beta-cell autoimmunity. Diabetologia. 2001;44:63–69.
42. Eidelman AI, Schanler RJ. Policy statement: breastfeeding and the use of human milk. From the American Academy of Pediatrics. Pediatrics. 2012;129:827–841.
43. Scharf RJ, Demmer RT, DeBoer MD. Longitudinal evaluation of milk type consumed and weight status in preschoolers. Arch Dis Child. 2013; 98:335-340.
44. Chen M, Pan A, Malik VS, Hu FB. Effects of dairy intake on body weight and fat: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012;96:735-747.
45. Gartner LM, Morton J, Lawrence RA, et al. Breastfeeding and the use of human milk. Pediatrics. 2005;115:496–506.
46. Pennington JAT, Douglass JS. Bowes and Church’s Food Values of Portions Commonly Used. 18th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005.
47. Lucassen PL, Assendelft WJ, van Eijk JT, Gubbels JW, Douwes AC, van Geldrop WJ. Systematic review of the occurrence of infantile colic in the community. Arch Dis Child. 2001;84:398–403.
48. Jarvinen KM, Makinen-Kiljunen S, Suomalainen H. Cow’s milk challenge through human milk evoked immune responses in infants with cow’s milk allergy. J Pediatr. 1999;135:506–512.
49. Paronen J, Bjorksten B, Hattevig G, Akerblom HK, Vaarala O. Effect of maternal diet during lactation on development of bovine insulin-binding antibodies in children at risk for allergy. J Allergy Clin Immunol. 2000;106:302–306.
50. Sampson HA. Food allergy. Part 1: immunopathogenesis and clinical disorders. J Allergy Clin Immunol. 2004;113:805–819.
51. Host A. Frequency of cow’s milk allergy in childhood. Ann Allergy Asthma Immunol. 2002;89(6 Suppl 1):33–37.
52. Iacono G, Cavataio F, Montalto G, et al. Intolerance of cow’s milk and chronic constipation in children. N Engl J Med. 1998;339:1100–1104.