bone health is complex, and there are many lifestyle-related factors at play
dairy products are the best source of calcium, which is the main mineral in bones.
therefore, health authorities recommend consuming dairy products every day.
but many people wonder if dairy products are really needed in their diet.
this evidence-based review looks at science.
from an evolutionary point of view, it doesn't make sense to eat dairy products
the idea that adults "need" dairy products in their diets don't seem to make much sense.
humans are the only animals that consume dairy products after weaning and eat milk from other species.
before animals were domesticated, milk was likely a rare delicacy that only babies could enjoy. however, it is unclear to what extent hunter-gatherers are looking for milk from wild animals.
given that adults may have consumed very little milk for most of their evolution, it is safe to assume that humans received all the calcium they needed from other dietary sources. (1）。
however, although dairy products are not needed in the human diet, this does not mean that it does not have benefits. this is especially true for people who cannot get large amounts of calcium from other dietary sources.
summary: on an evolutionary scale, humans have been consuming dairy products for a relatively short period. they are also the only species that consume milk after weaning or from other species.
osteoporosis quick start
osteoporosis is a progressive disease in which bones degenerate over time, losing mass and minerals.
the name very much describes the nature of the disease: osteoporosis = porous bone.
it has many different causes and factors that are completely unrelated to nutrition, such as exercise and hormones (2, 3).
osteoporosis is more common in women than in men, especially after menopause. it significantly increases the risk of fractures, which can have a very negative impact on quality of life.
why calcium is important
your bones play a structural role, but they are also your body's main reservoir of calcium, which has a variety of basic functions in the body.
your body maintains the calcium levels in your blood within a narrow range. if you don't get calcium from your diet, your body extracts calcium from your bones to maintain other functions that are more important for immediate survival.
a certain amount of calcium is constantly excreted from the urine. if your dietary intake doesn't make up for the lost parts, your bones 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 is the leading cause of fractures in the elderly.
the myth that protein lowers bone health
although dairy products contain a lot of calcium, some people believe that their high protein content can cause osteoporosis.
the reason is that when protein is digested, it increases the acidity of the blood. the body then extracts calcium from the blood to neutralize the acid.
this is the theoretical basis of the acid-base diet, that is, to choose foods with a net alkaline effect and avoid "acidifying" foods.
however, this theory really doesn't have much scientific support.
if anything, the high protein content of dairy products is a good thing. studies consistently show that eating more protein improves bone health (4, 5, 6, 7).
DAIRY PRODUCTS ARE NOT ONLY RICH IN PROTEIN AND CALCIUM, BUT ALSO RICH IN PHOSPHORUS. FULL-FAT DAIRY PRODUCTS FROM GRASS-FED COWS ALSO CONTAIN SOME VITAMIN K2.
Protein, phosphorus, and vitamin K2 are all important for bone health (8, 9).
summary: dairy products are not only rich in calcium but also contain a lot of protein and phosphorus, all of which are important for optimal bone health.
the results of the study were mixed
some observational studies have shown that increasing dairy intake has no effect on bone health and may even be harmful. （10, 11）。
however, most studies have shown a clear association between high dairy intake and a reduced risk of osteoporosis. （12, 13, 14）。
the truth is that observational studies often provide mixed results. they are designed to detect associations, but cannot prove causation.
fortunately, randomized controlled trials (true scientific experiments) can give us a clearer answer, as described in the next chapter.
summary: some observational studies have shown that dairy intake is associated with adverse effects on bone health. however, more observational studies have shown beneficial effects.
high-quality studies have shown that dairy products are effective
the only way to determine nutritional causation is to conduct randomized controlled trials.
this type of research is the "gold standard" of science.
it involves dividing people into different groups. one group received the intervention (in this case, eating more dairy products), while the other group did nothing and continued to eat normally.
many such studies have examined the effects of dairy and calcium on bone health. most of them have come to the same conclusion – dairy or calcium supplements are effective.
- childhood: dairy and calcium promote bone growth (15, 16, 17).
- adulthood: dairy products reduce bone loss rates and increase bone density (18, 19, 20).
- older adults: calcium supplementation improves bone density and reduces fracture risk (21, 22, 23).
in randomized controlled trials in each age group, dairy products consistently improved bone health. that's all that matters.
Vitamin D-rich milk appears to be more effective at strengthening bones (24).
however, be careful with calcium supplements. several studies have linked them to an increased risk of heart attack (25, 26).
it is best to obtain calcium from dairy products or other calcium-containing foods, such as green leafy vegetables and fish.
summary: multiple randomized controlled trials have shown that dairy products improve bone health in all age groups.
Conclusion
bone health is complex, and there are many lifestyle-related factors at play.
dietary calcium is one of the most important calcium. to improve or maintain bone health, you need to get enough calcium from your diet.
in the modern diet, dairy products provide most of the demand for calcium.
while there are many other calcium-rich foods to choose from, dairy products are one of the best sources you can find.