Dairy products are the best sources of calcium, and calcium is the main mineral in bones.
For this reason, health authorities recommend consuming dairy products every day.
But many people wonder whether they really need dairy in their diet.
This evidence-based review looks into the science.
The idea that adult humans "need" dairy in their diet doesn’t seem to make much sense.
Human beings are the only animal that consumes dairy after weaning and consumes the milk of another species.
Before animals were domesticated, milk was likely a rare delicacy only reserved for infants. Yet, it’s unclear to what extent hunter-gatherers sought out the milk of wild animals.
Given that milk intake was probably rare among adults during most of human evolution, it’s safe to assume that humans were getting all the calcium they needed from other dietary sources ().
However, even though dairy isn't necessary in the human diet, that doesn’t mean it can't be beneficial. This especially applies to people who do not get much calcium from other dietary sources.
Summary Humans have been consuming dairy for a relatively short time on an evolutionary scale. They are also the only species that consumes milk after weaning or from another species.
Osteoporosis is a progressive disease in which bones deteriorate, losing mass and minerals over time.
The name is very descriptive of the nature of the disease: osteoporosis = porous bones.
It has many different causes and factors that are completely unrelated to nutrition, such as exercise and hormones (, ).
Osteoporosis is much more common in women than in men, especially after menopause. It significantly increases the risk of bone fractures, which can have a very negative effect on quality of life.
Why Calcium Is Important
Your bones serve a structural role, but they are also your body’s main reservoirs of calcium, which has multiple essential functions in the body.
Your body maintains blood levels of calcium within a narrow range. If you're not getting calcium from the diet, your body pulls it from your bones to sustain other functions that are more important for immediate survival.
Some amount of calcium is continually excreted in the urine. If your dietary intake doesn't compensate for what is lost, your bones will lose calcium over time, making them less dense and more likely to break.
Summary Osteoporosis is a common disease in Western countries, especially in postmenopausal women. It’s a leading cause of fractures in the elderly.
Despite all the calcium that dairy contains, some believe that its high protein content can cause osteoporosis.
The reason is that when protein is digested, it increases the acidity of the blood. The body then pulls calcium from the blood to neutralize the acid.
This is the theoretical basis for the acid-alkaline diet, which is based on choosing foods that have a net alkaline effect and avoiding foods that are "acid forming."
However, there really isn't much scientific support for this theory.
If anything, the high protein content of dairy is a good thing. Studies consistently show that eating more protein leads to improved bone health (, , , ).
Not only is dairy rich in protein and calcium, it’s also loaded with phosphorus. Full-fat dairy from grass-fed cows also contains some vitamin K2.
Protein, phosphorus and vitamin K2 are all very important for bone health (, ).
Summary Not only is dairy rich in calcium, it also contains large amounts of protein and phosphorus, all of which are important for optimal bone health.
A few observational studies show that increased dairy intake has no effects on bone health or may even be harmful (, ).
However, the majority of studies show a clear association between high dairy intake and a reduced risk of osteoporosis (, , ).
The truth is that observational studies often provide a mixed bag of results. They are designed to detect associations, but can't prove cause and effect.
Luckily, randomized controlled trials (real scientific experiments) can give us a clearer answer, as explained in the next chapter.
Summary Some observational studies show that dairy intake is linked to a detrimental effect on bone health. However, even more observational studies show beneficial effects.
The only way to determine cause and effect in nutrition is to conduct a randomized controlled trial.
This type of study is the "gold standard" of science.
It involves separating people into different groups. One group receives an intervention (in this case, eats more dairy), while the other group does nothing and continues to eat normally.
Many such studies have examined the effects of dairy and calcium on bone health. Most of them lead to the same conclusion — dairy works.
- Childhood: Dairy and calcium lead to increased bone growth (, , ).
- Adulthood: Dairy decreases the rate of bone loss and leads to improved bone density (, , ).
- Elderly: Dairy improves bone density and lowers the risk of fractures (, , ).
Dairy has consistently led to improved bone health in randomized controlled trials in every age group. That's what counts.
Milk that is fortified with vitamin D seems to be even more effective at strengthening bones ().
However, be careful with calcium supplements. Some studies have associated them with an increased risk of heart attacks (, ).
It’s best to get your calcium from dairy or other foods that contain calcium, such as leafy greens and fish.
Summary Multiple randomized controlled trials show that dairy products lead to improved bone health in all age groups.
Bone health is complex, and there are many lifestyle-related factors at play.
Dietary calcium is one of the most important. To improve or maintain your bone health, you need to get adequate amounts of calcium from your diet.
In the modern diet, dairy provides a large percentage of people’s calcium requirements.
While there are many other calcium-rich foods to choose from, dairy is one of the best sources you can find.