Growing up, I was always told to drink my milk in order to have strong bones. Dairy is a regular part of my diet. I have yogurt or cereal nearly every morning, and avidly eat cheese and ice cream. I never thought anything of this until my friend told me the theory of how dairy is unnatural. Humans are the only species to consume milk from other animals. It’s quite weird honestly, why are we drinking something that is intended to make calves grow? Back in the olden days, humans only drank milk from their mother’s breast as infants. This is because they, without choice, thrived on a paleo diet. This diet consists of meat, fish, eggs, vegetables, fruits nuts, etc. A paleo diet avoids processed foods, sugar, dairy products, etc. This proves an argument that dairy products, such as milk, are not needed for health reasons. 

About 11,000 years ago, milk was essentially toxic. When we were infants our bodies produced an enzyme called lactase which allows us to break down our mother’s milk. But as we grow older and do not rely on our mother’s milk, we often lose this enzyme. Cattle herders leaned how to reduce lactose in dairy products to tolerable levels. It is believed that humans adapted to accommodate dairy products in their diet through the process of natural selection. But as we know there are still many people who are lactose intolerant. According to Authority Nutrition, about 75% (3/4) of the world’s population is unable to break down lactose. 

In 1951, a Harvard Nutritionist named Mark Hegsted conducted a study to find out if so much dairy was necessary for the human body. He study 10 men who were locked up in a prison in Peru. These man survived on rice and beans, with maybe one class of milk a week. He compared the calcium intake with the amount they released in their waste in order to figure out how much calcium they actually retained. He found that these prisoners could take in only 126 milligrams (less than a single glass of milk) and tests would still say they have normal levels of calcium in their body. There are many factors that make this study weak. They study was very small, only 10 people and did not climate third variables. The study also did not test women. It is known that women often need more calcium when they are pregnant or menstruating. This study alone does not strongly prove that dairy is unnecessary but it did inspire more research on the topic.

Walter Willett, who leads the nutrition department at Harvard University, starting to build off of Hegsted’s ideas. In 1977, Willet published the results of a eight-year long survey study. This study focused on the calcium intake of 43,000 men. The men received questioners about which foods they were eating, how often, and how much of each. The study separated the calcium intake from non-dairy sources and dairy sources. The validity of this experiment was tested by comparing the results to another random sample of 127 men. Nutrient intakes from the questionnaire were compared with the nutrients from this study. It was reported that there was a correlation coefficient of 0.61 for total calcium, 0.88 for skim or low fat milk, and 0.67 for whole milk. This proves that the study was valid because there was a high correlation rate. The study was also large enough to rule out third variables and produce accurate results. The study continued to compare these nutritional datas with injury rates. The participate were asked to report incidents of forearm and hip fractures, including the exact place and date of the occurrence. The study observed that there was no clear associated between calcium intake and  fracture incidents. So despite doctors long beliefs that calcium prevents broken bones, this study found no relationship between calcium intake and risk of fracture.

Willet continued to further study the roles of calcium on injuries and continued to find there was no relationships. After eight epidemiological studies and five randomized, controlled trials he concluded that, “calcium intake does not significantly decrease the risk of hip fracture in women or men.” Willet also conducted studies finding that men who drank two or more glasses of milk a day were nearly twice as likely to develop prostate cancer compared to those who drank no milk. A meta-analysis published in the American Journal of Clinical Nutrition last year concluded that “high intakes of dairy products…may increase total prostate cancer risk.” On the National Post, Willet stated, “(the dairy story) is very complex and we don’t have all the answers,” So far, studies have only reported a correlation between dairy consumption and the cancerous disease. Scientist have yet to understand how or why dairy could cause cancer. 

I think that all of Willet studies are well conducted and valid. There are many studies that prove the same results, therefor his conclusion are not a fluke. As stated above, there is still more research to be done to completely understand the working on dairy on our body but Willet has made some astounding discoveries that will influence more research and awareness about the topic.