For thousands of years, milk and dairy products have been a staple in many people’s diets. Globally, more than 6 billion people consume them. It’s believed dairy consumption began around 8000 BC in what is now Turkey. From there, it spread to other parts of Europe, Africa, Middle East and Asia. Despite the long track record with dairy, the health benefits have come into question with people wondering if dairy is bad for you. But is the criticism warranted?
The Nutrition of Dairy
Milk is defined as a fluid secreted by the mammary glands of females for the nourishment of their young. As a result, milk contains a number of essential nutrients. And at times, milk was relied on as a clean source of water when no other could be found. While cows are the most common source, goats, water buffalo and sheep are also used as sources of milk for humans.
Key among the nutrients is calcium. Calcium is needed for numerous actions from muscle contraction to bone development. Dairy products have some of the highest concentrations of calcium. Of which, about a third is absorbed. This is higher than most, but not all foods. Foods such as bok choy, broccoli and kale have higher calcium absorption, but don’t have as high a calcium content. Other high sources of calcium include canned sardines and salmon with bones (you need to eat the bones for the calcium).
Dairy also includes vitamins A, D (most milk is fortified with vitamin D) and B12, along with riboflavin and phosphorus. The latter of which is also needed for bone development. And dairy products are a good source of protein containing all nine essential amino acids.
Global Consumption of Milk and Dairy
While dairy products are consumed around the world, intake differs from country to country. Consumption is highest in Western and Northern Europe, North America and Australia and lowest in East and Southeast Asia, and Sub-Saharan Africa. Common among regions with low dairy intake is intolerance to lactose, the sugar found in milk. However, lactose is substantially lower in dairy products such as cheese and yoghurt.
The country with the greatest consumption of dairy is Finland. At approximately 450 kg per year per person, this equates to roughly 1875 glasses of milk per year. Or five per day. Of course not all of that is milk as some is cheese, yoghurt and other dairy products. In contrast, people in the Philippines consume the equivalent of five glasses per year.
Globally, milk consumption has been increasing in recent decades. This is driven mainly by countries with lower intake. For example, dairy consumption in China doubled from 1992 to 2012, and continues to increase. In countries such as Canada and the United States, consumption has plateaued and may even be decreasing.
Milk and Heart Health
Often promoted as a vital source of nutrients throughout the centuries, milk and dairy products have been questioned regarding the effects on long-term health. The predominant concern is due to the cholesterol and saturated fats in dairy.
However, dietary cholesterol is largely unrelated to blood cholesterol. As a result, the US 2015 Dietary Guidelines for Americans no longer recommend a limit on dietary cholesterol. And many other countries never had a cholesterol limit to begin with. In recent years, the health concerns of saturated fat have also been challenged. And a study in over 400 000 participants found milk consumption was actually associated with lower blood cholesterol.
When it comes to heart disease, the concerns of dairy don’t pan out. Compared to a typical Western diet, dairy intake had no effect on risk for heart disease. And in a global study, >2 servings per day of dairy was associated with lower chances of heart disease in regions with low dairy intake (China, Southeast Asia).
Effects on Other Health Conditions
Heart health isn’t the only thing that matters. Drinking milk has been associated with a higher (albeit small) chance for breast cancer, while cheese and yoghurt had no effect. However, not all studies have found an association and some have found dairy to be associated with lower chances for breast cancer. In terms of other cancers, studies have been consistent in dairy being associated with a lower risk for colorectal and bladder cancers. In contrast, high dairy intake (>5 servings per day) may be associated with a greater chance for prostate cancer in men.
Probably the most commonly known health benefit of dairy is on bones. Calcium is needed for bone development and it’s also relatively easy to meet your body’s calcium needs with dairy. Studies have demonstrated dairy intake can increase bone mineral density in children and adults. Whether milk and dairy can prevent bone fractures is unclear. One study found higher rates of fractures in older adults who drank milk (≥3 glasses/day), but lower rates in those consuming cheese and yoghurt.
Dairy and Life Expectancy
The effects of dairy on early death seem to depend on the type of dairy. Having >2-3 servings of milk (non-fermented dairy) per day has been associated with a slight increased chance of early death in studies from Sweden and the United States. At lower amounts of milk, there was no effect on early death. This is consistent with an earlier review of studies which also found no association.
In regions with low dairy intake, such as China and Southeast Asia, milk consumption (as well as other dairy) may lower risk for early death. This may be due to the lower quality of the overall diet in these regions, and the nutritional benefits of milk.
In contrast, these same studies reported consumption of fermented products, such as cheese and yoghurt, was associated with greater life expectancy. In addition, this finding has been reported across numerous other studies. It’s unclear why there may be a difference between fermented and non-fermented dairy. Since both products contain high levels of saturated fat, it’s unlikely to be due to fat content.
The caution with these studies is they all have the limitations common to dietary research. They’re observational in nature, which means one cannot draw conclusions as to whether milk and dairy products are protective or not. Randomized trials are needed for that. In part because consumption of dairy may be linked to other behaviours. Indeed, one study found people who drank milk also had higher smoking rates. In addition, whether a food is beneficial or not often comes down to what it’s replaced with. Replacing dairy with sugars and other simple carbohydrates is different than replacing with fruits and vegetables.
This doesn’t mean one needs to consume dairy. Indeed, similar nutrition can come from other food sources. And people may have valid reasons for not eating dairy products. On the other hand, dairy products in moderation do not appear to be as problematic as some have suggested. And in particular, the concerns with fat from dairy may be unwarranted.
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