I’ve already examined the ideas of The Alkaline Diet on this blog before, noting that the evidence suggests there is some merit to the role of acid forming foods and bone loss (1). However, just because a food is acid forming does not mean it is therefore bad for your bones. I believe meat is such an exception.
Meat is lambasted in some circles as being acid forming (due to the protein) and therefore bad for bones. This is further supported by studies showing increasing protein leads to increased calcium loss in urine, as demonstrated by this graph, a composite of data from 26 studies:
So if increasing dietary protein increases calcium lost in the urine, does this mean increasing protein causes you to pee away your bones? No way! Although protein increases the calcium lost via urine, it also increases the calcium absorbed in your stomach and intestines. Ultimately, studies show that protein is not bad for your bones and too little protein is more of a risk than too much.
In a study on elderly people (3), the authors concluded that “Increasing protein intake from 0.78 to 1.55 g/kg/d with meat supplements…when exchanged isocalorically for carbohydrates, may have a favorable impact on the skeleton in healthy older men and women”.
Another study (4) found that increasing protein calories from 12% to 20% using meat did not negatively affect bone status in post menopausal women.
In a series of studies by Jane Kerstetter et al. (2), increasing protein from low to moderate levels using mainly meat improved bone health and further increases did not adversely affect bone health. Their paper discusses in depth the finding that too little protein is bad for bones, including for visualization purposes a graph on the positive association between total dietary protein intake and bone mineral density in elderly men and women participating in the Rancho Bernardino study:
One study found that (5) “Under practical dietary conditions, increased dietary protein from animal sources was not detrimental to calcium balance or short-term indicators of bone health”.
An older study measuring the calcium needs of Peruvian Prisoners found that increasing meat in the diet from 100g to 300g brought about an more positive calcium balance (9)
Another study by Jane Kerstetter et al. (6) increased protein intake in women from 1 to 2.1 g/kg. The authors wrote “These data directly demonstrate that, at least in the short term, high-protein diets are not detrimental to bone”. Meats such as fish and poultry were the main food sources used to increase protein.
A 6 month weight loss study fed overweight participants low and high protein diets (70.4 vs. 107.8 grams per day) and measured bone mineral loss (8). No adverse affects on bone loss were seen in the high protein group and additionally, the high protein group experienced greater weight loss. Increases protein came primarily from diary and meat. This study is arguably weak however, due to a much lower intake of calcium in the low protein group.
A weight loss study on overweight individuals found that increasing protein in place of carbohydrates did not change urinary calcium levels or several markers of bone turnover (13). About half of the protein in the study was provided by meat.
Finally, a study which had women increase protein intake from 61 to 118 grams a day, provides more evidence that “a high-protein diet has no adverse effects on bone health” (7). The increase in protein in was achieved primarily by “increasing portions of meat protein (mainly from beef)”.
But is it protein in general that produces these effects? Well, several studies have found that increasing protein intake using mixtures of mostly wheat gluten and dairy proteins have produced negative effects on calcium balance (10,11,12). So the answer is no, not all protein sources will necessarily be good for bone health, some may even be bad. Still, this does not apply to meat.
If you’re concerned with your bone health, avoiding meat appears to be at best not helpful and at worst actually bad for the health of your skeleton.