You may have seen news reports of a study that was just published at the very end of October (2014) in the British Medical Journal by Karl Michaelsson and a team of Swedish researchers that suggests that cow’s milk might actually increase your risk of death and bone fractures. And you may be wondering if you should be drinking cow’s milk anymore. And what about other dairy products? Are these helpful or potentially harmful for your bones? What’s the bottom line on this research. Well, first I’ll share what the researchers wrote in their article and what they hypothesized. Then we’ll critique the study and see how good a job they did in collecting their data and whether it’s reasonable. And then I will makes some suggestions for you and you can make up your mind for what is the best for you and your bones.
So in the study by Michaelsson and his team, high cow’s milk consumption, which they considered to be 3 or more glasses of cow’s milk everyday, was associated with an increase risk of death in a large group of Swedish women. They looked at 61,433 women and they followed them for 20 years. They also looked at a large group of men 45,335 men who were also followed for 20 years, but milk consumption had virtually no effect on the men. So the women who were drinking 3 or more glasses a day were found to have almost double the risk of death for many cause: all-cause mortality, compared to women drinking less than a glass of milk a day. And every glass that the women drank, increased her risk of death by 15% according to this research. And also higher milk consumption did not provide any protection against fracture. In fact, women who were drinking 3 or more glasses of milk a day had a 13% increased risk of hip fracture. So this sounds pretty bad.
But the question is, does this association really hold up, is it an association that was a confounder from this research or is this a real effect of drinking cow’s milk and if so, why might this be?
We’ve been told for many years, many many studies have shown that a diet rich in milk, dairy products will reduce our risk of fractures. Why? Because (dairy) calcium contains 18 of 22 essential nutrients including significant amounts of calcium and vitamin D that are crucial for heathy bones. But a high intake of milk, could have undesirable effects and the reason why is milk contains a sugar called lactose, which is broken down in our digestive tract by an enzyme called lactase, and it produces two sugars: glucose and galactose. And galactose can be a problem for some people. Galactose can increase chronic inflammation and if you’ve read my book “Your Bones” you know that inflammation from any source can activate your osteoclasts and can promote excessive bone remodelling. Animal studies in a number of species have shown that chronic exposure of high levels of galactose can be harmful. In fact, researchers give lab rats injections of d-galactose or add it to the animals diet to cause accelerates aging, so they can study accelerated aging. D-galactose given to mice, rats and drosophila flies is an established and experimental model to cause premature aging, and shortened lifespan due to excessive pre radical production and chronic inflammation. So the theory is that even a low level of d-galactose can be harmful and based on a concentration of lactose in milk of approximately 5%, one glass of milk can deliver up to 5 grams of d-galactose, which is equivalent to the amount they use in animal studies to promote accelerated aging in lab animals. So the bottom line here is that d-galactose does increase oxidative stress and it does help promote chronic low grade inflammation which is well recognized to promote cardiovascular disease, cancer and age-related bone loss and muscle wasting. So, there are a bunch of markers that are associated with inflammation that they did find in people in the Swedish study that they were elevated and they indicate higher inflammation potential due to the galactose. So the Swedish researchers who published this study are arguing that milk is a problem for a lot of people, and if so, it might be a good idea not to drink 3 or more glasses of lactose containing milk.
But what about other dairy products like milk or cheese or kefir?
Cheeses, particularly hard cheeses and fermented dairy products like yogurt contain virtually no lactose. So we don’t produce galactose when we consume them and not surprisingly in this study, it was not shown to produce high levels of the pro-inflammatory markers that they saw in the people drinking more milk. Cheese, yogurt etc. were fine. In fact, women with a higher intake of cheese or fermented milk products like yogurt had a lower fracture rate and lower mortality compared to women with low intakes of cheese and yogurt. And also remember that cheeses and yogurts, especially if they are from animals that are kept on pasture and eat grass, those cheeses and yogurts are going to have really good amounts of vitamin K2, which is also essential for healthy bones.
So, should we trust this study? How reliable was the data that was collected?
Well, the researchers based their findings on two frequency questionnaires and lifestyle questionnaires. One which was sent to women along with an invitation to have a routine mammography screening sometime between 1987 and 1990. And then a second one that was sent in 1997. Men received one questionnaire covering their diet and participants were asked in these questionnaires how many servings a day or a week they consumed of common foods including fermented milk products like yogurt and cheese.
In other words, participants were asked twice in 20 years, what they were drinking and eating and how much.
And so I’ll ask you how accurately do you remember what you ate everyday, last week. Does what you eat daily change from day to day or week to week? From season to season? Or from month to month? Would two frequency questionnaire sent to you over a very long time span accurately sum up what you are actually consuming?
And what about other recent studies. Do they confirm this Swedish study’s findings?
The answer to this is no.
Two recent studies. One published in the Bone and Mineral Research in 2014 by a group led by Sahni (lead researcher: S. Sahni) – it was published in August so one month before the Swedish study came out, suggests the opposite, that people consuming at least 7 or more servings a week had a 42 percent lower risk of hip fracture compared to those who were consuming less than one serving per week. And yogurt was found to be protective to. The researchers conclusion from this was that greater intakes of milk and milk and yogurt can lower the risk of hip fracture in older adults. The same group of researchers led by Sahni, had published an earlier paper a year ago in 2013 and this was a 12 year study that looked at the risk of hip fracture in the now, grown up children of the original participants in the Framingham Study. So Americans – they looked at 3212 participants they had them complete a frequency food questionnaire and they followed them for 12 years to see how many of them had a hip fracture. The bottom line in this study is that people who had higher intakes of milk and yogurt had higher BMD and were at a lower risk for hip fractures.
So what’s my takeaway from all these conflicting research studies?
The vast majority of studies indicate that dairy products are beneficial for us and can help us have healthier bones. If you’re not allergic to dairy products, keep enjoying them! If you have an inflammatory condition, say arthritis or blood pressure or cardiovascular disease or diabetes you might want to consider lessening your consumption of cow’s milk that contains lactose in it so you lessen your intake of d-galatcose in case it might be harmful. And be sure to enjoy fermented dairy foods like yogurt and cheese. I think they will serve you and your bones very well. Thanks so much for tuning in and I hope this information has been helpful for you.