Protein and Bone Health

Does animal protein in our diet result in higher risk of bone fractures and osteoporosis? It appears so! Our co-founder, Dr. Sofia Pineda Ochoa, discusses the clinical epidemiological studies that have found a strong, positive association between animal protein intake and risk of bone fractures. The protein causes acidosis in our bodies when we metabolize it, and one of the mechanisms used to neutralize that acidity appears to be leaching calcium from our bones.

The first part of the transcript is included below for reference, and the full transcript (which is too long to have here) is available on our website with sources and credits at this link: http://meatyourfuture.com/2015/05/hea...

[The following transcript is an approximation of the audio in video. To hear the audio and see the accompanying visuals, please play the video.]

PARTIAL TRANSCRIPT:

Harvard’s School of Public Health explains very nicely the mechanism by which protein can cause problems for bone health. It says, “as your body digests protein, it releases acids into the bloodstream, which the body neutralizes by drawing calcium from the bones. Following a high-protein diet for a few weeks probably won’t have much effect on bone strength. Doing it for a long time, though, could weaken bone.”

Now we’ve known for a very long time that meats, including fish, are acid forming in our body. Scientists from Columbia University, back in 1912, analyzed acid and base forming elements in food, and noted that, “all the meats (including fish)…show a decided excess of acid-forming elements”; all the “meats (including fish) show [a] decided predominance of acid-forming elements.”

Back in 1920, Columbia’s Department of Chemistry also reported that adding meat to one’s diet results in increase of calcium loss in urine, thought to be because “the added meat gave to the diet as a whole an excess of acid-forming over base-forming mineral elements[.]”

And what have we seen from the results of the consumption of animal protein with regards to bones? Researchers from Yale University’s School of Medicine looked back across a broad array of thirty-four prior published studies across sixteen countries, and they found these studies over time showed “a strong, positive association” between dietary animal protein and female bone fracture rates.

So, we’ve known for some time that this association exists. We know eating a diet high in animal protein results in acidity, and that our body leaches calcium from our bones to buffer the acid. One of the mechanisms behind this phenomenon is that animal protein has a higher amount of sulfur containing amino acids, and the “sulfur-containing amino acids from animal protein lower blood pH”.

So animal proteins — including meat, fish, dairy, poultry or eggs — have higher amounts of sulfur-containing amino acids than plant foods. As a result, when we eat diets high in animal proteins, our body produces sulfuric acid, which increases the acidity in our bodies. One of the body’s mechanisms to neutralize this acidity is to draw calcium from our bones (similar, for example, to when we take antacids that are made with calcium to neutralize the acidity in our stomach associated with heartburn). The problem is that constantly leaching calcium from our bones can reduce bone mass, making our bones weak and more prone to fractures and osteoporosis. Moreover, the chronically higher calcium excreted in our urine can also lead to the development of kidney stones.

This Harvard study published in the American Journal of Epidemiology followed over 80,000 women over twelve years, and found that animal protein was associated with increased risk of forearm fracture, but no increase in risk was observed with higher intakes of vegetable protein. It found that women who consumed the largest amount of animal protein in the study had a 22% higher risk of fracture. Evidence suggests that “higher protein intakes in young…women have a negative impact on radial bone measurements”, meaning that women who consumed higher protein diets have been found to lose bone mineral content and bone density.

So we know that our body uses base stores (including calcium from our bones) to neutralize the acidity we get from our diet. This article from The Journal of Nutrition explains the same thing. It says, “diets that are net acid producing…induce and sustain increased acidity of [our] body fluid. With increasing age, the kidney’s ability to excrete daily net acid loads declines, invoking increased utilization of base stores ([from our] bone [and] skeletal muscle) on a daily basis to mitigate the otherwise increasing baseline metabolic acidosis, which results in increased calciuria and net losses of body calcium...

(Remainder of transcript, along with sources and credits, available here: http://meatyourfuture.com/2015/05/hea...]