Dairy products are the best sources of calcium in the diet and calcium is the main mineral in bones.
For this reason, the health authorities recommend that we consume three glasses of milk per day.
However, the situation appears to be a bit more complicated... the countries that consume the most dairy also have the most osteoporosis.
Dairy Doesn't Make Sense From an Evolutionary Perspective
The idea that humans "need" dairy doesn't make much sense to me, because we didn't consume dairy throughout evolution.
Human beings are the only animal that consumes dairy after weaning. We are also the only animal that consumes dairy from another species than our own.
For these reasons, consuming dairy may be considered "unnatural" and something that is relatively new to our species. We've been evolving for millions of years, only consuming dairy for about 10.000 years (sources on the exact number).
Then we have data showing that bone health was excellent in hunter-gatherers. They did not eat any dairy after weaning, but they did get significant amounts of calcium from other sources ().
So... it doesn't really make sense from an evolutionary perspective that humans would need dairy to optimize bone health.
However, even though it isn't needed, that does NOT mean that it can't be beneficial.
Bottom Line: Humans have been eating dairy for a relatively short time on an evolutionary scale. They are also the only species that consumes dairy after weaning, or dairy from another species than their own.
A Very Quick Primer on Osteoporosis
Osteoporosis is a progressive disease in which bones deteriorate, losing mass and minerals over time.
The name is very descriptive for the nature of the disease.
Osteoporosis = porous bones.
It has many different causes and factors completely unrelated to nutrition can be very important, such as exercise and hormones.
Osteoporosis is much more common in women, especially after menopause. Having osteoporosis significantly increases the risk of bone fractures, which can have a dramatic negative effect on quality of life.
Why Calcium is Important
Your bones serve a structural role, but they can also be considered as "reservoirs" for calcium, which has many other functions in the body.
The body maintains blood levels of calcium within a narrow range. If you're not getting calcium from the diet, then the body pulls calcium from the bones in order to sustain other functions 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 from your body, then over time your bones will lose calcium, making the bones less dense and more likely to break.
Bottom Line: Osteoporosis is a common disease in Western countries, especially in postmenopausal women. It is a leading cause of fractures in the elderly.
The Myth About Protein and Bone Health
Some people believe that despite all the calcium, dairy can cause osteoporosis because it is high in protein.
The reasoning is that when protein is digested, it increases the acidity of the blood. Then the body pulls calcium from the blood in order to neutralize the acid.
This is the theoretical basis for the acid-alkaline diet, which is supposedly 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 .
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 is also loaded with phosphorus. Full-fat dairy from grass-fed cows also contains large amounts of .
Protein, Phosphorus and K2 are all very important for bone health (, , ).
Bottom Line: Not only is dairy rich in calcium, it also contains large amounts of protein, phosphorus and Vitamin K2, all of which are important for optimal bone health.
Studies Where Dairy Has Negative Effects
There are some observational studies showing that increased dairy is associated with negligible or harmful effects on bone health (, ).
These studies are often cited by vegans and other people who are against dairy for some reason, but they carefully ignore all the other studies where dairy has positive effects (, , ).
The truth is that observational studies often give a mixed bag of results and they can't be used to prove anything.
That being said, there are many more observational studies showing beneficial effects than there are showing no effect.
Luckily for us, we also do have plenty of real scientific experiments (randomized controlled trials) that can give us a clear answer of the effects that dairy products can have on our bones.
Bottom Line: There are some observational studies showing that dairy has no effect or a detrimental effect on bone health. However, there are even more observational studies showing beneficial effects.
"Real" Science Disagrees - Dairy Works
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: During childhood, dairy and calcium lead to increased bone growth (, , ).
- Adulthood: In adults, increased dairy decreases the rate of bone loss and leads to improved bone density (, , ).
- Elderly: In the elderly, dairy improves bone density and lowers the risk of fractures (, , ).
Dairy has consistently led to improved bone health in multiple randomized controlled trials, in every age group. That's what counts, period.
However, I must warn against the use of calcium supplements. Some studies show that they can increase the risk of heart attacks (, ).
It is best to get your calcium from dairy or other foods that contain calcium, such as leafy greens and fish.
Bottom Line: Multiple randomized controlled trials show that dairy products lead to improved bone health in every age group.
Dairy Isn't "Needed" For Bone Health, But it Does Have a Benefit
If you've been following my blog for a while, then you will know that I am NOT a fan of the conventional nutritional wisdom.
However, they appear to be right about dairy, which IS good for bone health, at least in the context of a Western diet.
There are so many studies to support it that it is pretty much scientifically proven.
However, even though dairy has beneficial effects, I do not think that it is "needed" because it doesn't make evolutionary sense. It is very possible to maintain optimal bone health without dairy.
Bone health is complex and there are many lifestyle-related factors at play.
These include doing resistance exercise, getting adequate protein, Vitamin D and magnesium, as well as eating besides dairy.