We had whole milk delivered to the house in glass bottles when I was a kid. My dad spent many years as a veterinarian specializing in work for one of the largest milk processors in the Midwest, and the herds of dairy cattle that supplied it. I always marveled at the large dairy farms, the hard working dairy farmers, and the huge tanks of milk they produced. And we grew up drinking milk, lots of milk. After all, milk “does a body good”. We all know milk is good for building strong bones… right?
The Swedish Study
Not according to a 2014 study in the British Medical Journal titled “Milk Intake and Risk of Mortality and Fractures in Women and Men”. The authors, Karl Michaëlsson, et al, analyzed over 100,000 people from 3 counties in central Sweden. The study focused on the relation between milk intake and the risk of subsequent hip fractures, heart disease, and cancer.
Using food diary questionnaires the authors were able to separate the intake of non-fermented milk, typical of what we drink, and fermented milk products including yogurt and cheeses. The participants were observed over a 20-year period and their health outcomes were tracked using Sweden’s centralized healthcare records.
The results showed an increasing risk of hip fractures in women with each increase in the number of glasses of milk consumed each day. Women who had over 3 glasses of milk daily had a 60% increased rate of hip fractures compared to women drinking less than 1 glass of milk per day. Their risk of death from heart disease was increased 93% and they had a 70% increase in cancer mortality.
Interestingly, the consumption of cheese and yogurt showed the opposite; that is a lower risk of mortality and hip fractures. For each serving of fermented milk products the risk of mortality and hip fracture was about 10-15% less.
In men there was better news. Those who drank more than 3 glasses of milk daily only had a 10% increase risk in mortality, mostly from heart disease, when compared to those drinking less than one glass per day. There was no significant change in the risk of hip fractures in relation to milk intake, whether fermented or not.
To be fair, there are other studies that suggest milk may prevent hip fractures, such as one from the August 2014 issue of the Journal of Bone and Mineral Research titled “Protective association of milk intake on the risk of hip fracture” by Sahni et al. They conducted a similar study of 830 people over a 10-year period. Their results showed a 40% reduction in hip fractures in the people drinking the most milk, with no benefit from the fermented cheese and yogurt.
Another study, “Milk and yogurt consumption are linked with higher bone mineral density but not with hip fracture” from the 2013 Archives of Osteoporosis, showed that increased milk consumption led to slight improvement in bone mineral density noted on Xray, but no significant change in risk of hip fractures. This study found that cream intake was associated with a slight worsening of bone mineral density, suggesting not all dairy products have the same effect on bone.
My review of these, and a dozen or so other studies, including observational and randomized double-blinded trials, suggests that increased dairy intake leads to increases in bone mineral density, yet the evidence for reducing hip fractures is weak. Of note, several studies point out there may be significant differences between different milk products on bone formation, and other diseases.
What’s in Milk?
Milk is about 90% water. The main carbohydrate or sugar in milk is lactose, which must be broken down by an enzyme called lactase before it can be absorbed. Universally most human babies make lactase, but by age 7 or 8 the gene for making lactase “turns off”. As a result, only about 1/3 of adults worldwide can digest or tolerate milk. It is believed that a genetic mutation occurring in Europeans about seven to eight thousand years ago allowed the European continent to become the epicenter for milk drinkers. Most milk drinkers today can trace their ancestry to European descent.
One theory on why milk might be harmful is related to the breakdown of lactose into glucose and galactose. Research has shown galactose can induce inflammation in the body. The Michaëlsson study found higher levels of oxidative stress and inflammation markers in the milk drinkers, while the yogurt and cheese crowd had lower levels. This is consistent with fermentation of milk leading to a marked reduction in lactose. It may be that milk sugar is a culprit.
The two main proteins in milk are casein and whey. Human breast milk has a roughly 40:60 ratio of the two, while cows milk is about 80:20, and cows milk has about 3x the total protein content than human breast milk. Casein is a very common delayed food allergen, which makes for another potential source of inflammation.
Whey protein, when purified as an isolate or hydrolysate as it is found in a variety of powdered products, is a very nutritious protein supplement without any lactose or fat, containing all 9 essential amino acids. It is known to have many health benefits, from helping build muscle and lose weight, lowering blood pressure and cholesterol, and possibly having anti-cancer effects.
Fat is the last macronutrient in milk with about 2/3 of it is being saturated fat, which contributes to inflammation and higher cholesterol. There are small amounts of vitamins and minerals in milk.
Milk naturally contains a cocktail of hormones and growth factors, which are perfectly designed to grow a baby calf. However, these same factors may play a role in stimulating the growth of cancer in adult humans. For the most part, associations between cancer risk and intake of milk and dairy products are mixed. There seems to be a trend of lower rates of some cancers such as colon and bladder, higher rates of others such as prostate and testicular, and little effect on stomach and ovarian cancers associated with milk intake.
What’s a person to do? Supplement with whey protein powders that don’t contain lactose or milk fat. Enjoy fermented milk products such as cheese and yogurt, but be wary of delayed allergies to milk and moderate overall milk intake. If you were looking to milk for strong bones, I’d look elsewhere.
Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine. He specializes in Bioidentical Hormone Replacement for men and women, thyroid and adrenal disorders, fibromyalgia, weight loss and other complex medical conditions. He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com). Call (970) 245-6911 for an appointment or more information.