Does Milk Really Build Strong Bones?

In English 15A I had one stay assignment in which i was tasked with investigating a food that is largely considered ‘natural’ and investigate how it is processed and made. In my investigation, I researched the processing and production of milk, and found in my paper that milk is much more processed than one may think or be able to perceive. In my research, though, I came across several articles saying that milk is not as healthy for you as you think.

Many of us were taught from a young age that drinking milk is good for you because it has calcium that builds strong bones. However, the information that I found in my research heavy milk consumption can actually increase the risk of bone fractures, which is certainly surprising.

An titled “Is Milk Really bad for the Bones?” cites a BMJ study that looked into how milk intake correlates to bone fracture, death from cardiovascular disease, death from cancer, and death of any cause in a large group of Swedish men and women.

The study was a widespread longitudinal study, and observational in its nature. Over 100,000 Swedish men and women were given questionnaires in which they noted how often they ate certain foods. In a follow up twenty years later, 25% of the women had died, and almost 30% had bone fractures. Men had their follow-ups after an average of eleven years (the study was originally done to study women exclusively but then opened up to men a decade later) and the findings were similar; 22% of the men had died by the time of their follow up, and about 12% had bone fractures. The results of the study are heavy in statistics lingo, introducing a concept called adjusted hazard ratio. The adjusted mortality hazard ratio for three glasses of milk per day versus one glass of milk or less for women was 1.93, meaning women who drank a substantial amount of milk were almost twice as likely to die. In men, there was a slight increase in mortality, but it was less than five percent.

Given the fact that this study is observational, the results are inherently prone to confounding variables. The article additionally mentions the possibility of reverse causation, though I see very little possibility for this considering the study was longitudinal. Since the study is chronological, I do not see how milk intake could be caused by one’s death twenty years in the future. However, women could be drinking excessive amounts of milk because they were already at risk for bone disease, and thus their doctors told them to drink a lot of milk (Sakimura).

Traditional milk bottle with a glass full

Additionally, this study lacks generalizability. Could something about Swedish culture (diet, cultural practices, quality of doctors, etc.) lead to women having increased risk of bone fracture?

As such, there is no need to change your practices or stop drinking milk based on just this one study. However, it would not be wise to rely on milk alone to keep your bones healthy.

Lastly, as one WebMD  article notes, over fifty percent of adults are at risk for brittle bones. So, this increases the chance that this study is a poor barometer for milk’s effects. The countries that consume the most milk in their diets are the countries where osteoporosis is most commonly reported. This is a correlation, not a causation, but the connection there is notable. As it turns out, the link between calcium intake and bone health is very minimal, and the link between dairy consumption and strong bones is next to none (Goldschmidt).

Don’t stop drinking milk because of these findings, an absence of evidence is not always evidence of absence. Nonetheless, remember that if you are drinking milk with bone health in mind, you may be accomplishing much less than you previously thought.

1 thought on “Does Milk Really Build Strong Bones?

  1. Lauren Eve Ribeiro

    I found this post really interesting because personally i do not like the taste of milk. Because of this i have always had a calcium deficiency and doctors urge me to take more and have me take calcium supplements. But if milk isn’t as good as we think why do they urge me to drink it so much? Also in your blog it says that women who drank a lot of milk were more likely to die, did this study take into account any other variables? Such as other eating habits and lifestyle and health.

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