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The China Study authors state that:

osteoporosis is linked to the consumption of animal protein because animal protein, unlike plant protein, increases the acidity of blood and tissues. They add that to neutralize this acid, calcium (a very effective base) is pulled from the bones, which weakens them and puts them at greater risk for fracture." from Wikipedia

As noted, they found "in [their] rural China Study, where the animal to plant ratio [consumption of protein] was about 10 percent, the fracture rate is only one-fifth that of the U.S. (p. 205, 208)"

Does that mean that drinking milk actually can lead to osteoporosis, rather than prevent it?

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  • You are aware that milk is a pretty minimal source of animal protein, compared with (say) meat?
    – DJClayworth
    Mar 9, 2011 at 16:41
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    I would add that a) Milk is not a very significant source of protein; b) it is a significant source of calcium. On the basis of the premises of the question alone, there would be no reason to fear milk.
    – Marcin
    Mar 13, 2011 at 17:58
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    Whenever I hear "The China Study" I reach for my rawfoodsos.files.wordpress.com/2010/08/…
    – Goran
    May 27, 2011 at 7:18
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    Doesn't make sense, chemically. Proteins are buffers. They will only increase the acidity if it was low to start with; therefore the suggested mechanism can't even work.
    – MSalters
    May 27, 2011 at 8:38
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    People in rural china are also likely to have a lifestyle with far more physical activity than US Americans. Physical stress to bones is of huge importance for regulating the ongoing bone remodeling and in consequence also for bone health.
    – cbeleites unhappy with SX
    Nov 10, 2019 at 23:17

2 Answers 2

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Lanham-New et al.1 compared the literature for bone health in ovo-lacto-vegetarians and vegan diets against omnivores with predominantly meat diets. They found no difference in bone-health indices between those two groups.

This review indicates that the source of the dietary protein does not make a significant difference for bone health.

The claim that animal proteins increase the acidity of the blood is also not credible. The pH value of the blood and inside cells is tightly regulated2 and not easily influenced by diet. The content of the stomach there is already a very acidic environment, which shows that the pH can be effectively regulated by the body.

There are also several studies indicating that milk consumption has a positive effect on bone health and decreases the risk of osteoporosis:

Effects of calcium intake, milk and dairy product intake, and blood vitamin D level on osteoporosis risk in Korean adults: analysis of the 2008 and 2009 Korea National Health and Nutrition Examination Survey:

The results of this study showed that BMD increases as Ca intakes increases, and that the risk of osteoporosis incidence was reduced when more than 1 serving of milk or dairy products were consumed and serum 25(OH) vitamin D level was maintained in the normal range

Calcium, dairy products and osteoporosis:

Of 52 investigator-controlled calcium intervention studies, all but two showed better bone balance at high intakes, or greater bone gain during growth, or reduced bone loss in the elderly, or reduced fracture risk. [...] While most of the investigator-controlled studies used calcium supplements, six used dairy sources of calcium; all were positive. Most of the observational studies were based on dairy calcium also, since at the time the studies were done, higher calcium intakes meant higher dairy intakes.

[1] S.A. Lanham-Newa, W.T.K. Leea, D.J. Torgersonb and D.J. Millwarda, Is vegetable protein more beneficial to bone than animal protein?, International Congress Series 1297, Nutritional Aspects of Osteoporosis 2006. Proceedings of the 6th International Symposium on Nutritional Aspects of Osteoporosis (2006)

[2] Lodish et al., Molecular Cell Biology. 4th edition, New York: W. H. Freeman (2000).

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    +1 In addition to what you've said, blood pH is regulated by respiration, and rightly so because life (well, our life) is not possible outside a very, very narrow margin. The claim is really ridiculous. Also, milk is an important source of vitamin D (in northern countries with not so much sun even the main source), which prevents osteoporosis rather than causing it.
    – dm.skt
    Mar 11, 2011 at 23:07
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    @dm.skt, your claim that some part of milk prevents osteoporosis seems to be in conflict with @Fabian's reference claiming no significant difference. Can you provide a reference?
    – Oddthinking ♦
    May 5, 2011 at 15:24
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    This does not conflict with above study, you need to read carefully. The study merely claims that there was no significant difference in bone health between ovo-lacto-vegetarians and omnivores. In other words, no difference between people who drink milk and eat eggs, and people who drink milk (and eat everything). There is no "no milk" group in this comparison (and I daresay probably for a reason, the author probably didn't like the outcome...).
    – dm.skt
    May 5, 2011 at 16:30
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    @JohnC Specifically, ruminants, who need extra stomachs to get their nutrition in such a manner.
    – Dave
    Apr 22, 2012 at 3:38
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    @Dave, although oxen are ruminants, there are certainly herbivores that are not ruminants. For instance, horses eat grass, but only have a single stomach. Also gorillas, which have an extra-long intestine where bacteria help break down the cellulose they eat.
    – John C
    Apr 22, 2012 at 11:36
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Milk consumption and osteoporosis

In a large study in Sweden they observed an association between high milk consumption and increased incidence of osteoporosis, especially in women. The authors suggested that one possible explanation could be reverse causality: People who knew they were at increased risk of osteoporosis, for example, due to family history of osteoporosis, might drink more milk in an attempt to prevent osteoporosis, but they still developed it.

High milk intake was associated with higher mortality in one cohort of women and in another cohort of men, and with higher fracture incidence in women. Given the observational study designs with the inherent possibility of residual confounding and reverse causation phenomena, a cautious interpretation of the results is recommended.

Also, the evidence from several systematic reviews of studies in another answer shows that high milk/dairy intake is associated with a slightly decreased and not increased risk of osteoporosis and bone fractures.

Plant vs animal protein and osteoporosis

In addition to the review mentioned in another answer, in the following 2 study reviews, animal protein was not associated with increased rate of osteoporosis:

1) Animal versus plant protein and adult bone health: A systematic review and meta-analysis from the National Osteoporosis Foundation (PlosOne, 2018):

OBJECTIVE: The aim was to conduct a systematic review and meta-analysis evaluating the effects of animal versus plant protein intake on bone mineral density (BMD), bone mineral content (BMC) and select bone biomarkers in healthy adults.

CONCLUSION: These results do not support soy protein consumption as more advantageous than animal protein, or vice versa.

2) Acid diet (high-meat protein) effects on calcium metabolism and bone health (USDA.gov, 2010):

On the basis of recent findings, consuming protein (including that from meat) higher than current Recommended Dietary Allowance for protein is beneficial to calcium utilization and bone health, especially in the elderly.

In conclusion, there is no convincing evidence to say that milk or animal protein consumption is associated with an increased risk of osteoporosis.

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