Amy Berger, known as @TuitNutrition on Twitter, recently posted an excellent article on her blog about protein intake and its effect on bone density. Below we’ll offer a TL;DR and an additional comment on why the orthodox thoughts about it don’t make sense.
A Brief Summary Of The Issue>
The current thinking goes as follows: protein is considered to be an acidic nutrient. This doesn’t mean that it tastes acidic on your tongue, but rather that after digestion it leaves an acidic residue in your digestive system. Our bones consist of minerals – mostly calcium and magnesium – and collagen. When the acidity in our body spikes, we compensate by leeching minerals out of our bones since minerals are alkaline.
It turns out the opposite happens. Studies have shown that as protein intake increases, bone health seems to increase, not decrease. The reason came up with the wrong explanation is because increased protein intake is associated with increased calcium excretion, mostly through urine. What was not realized was that calcium absorption increased at the same time as calcium excretion. In short, nobody did the math on calcium in versus calcium out.
Another Reason The Theory Is Flawed
Here is something else to consider: the pH level of gastric acid is between 1.5 to 3.5. The scale goes from 0 to 14, with 0 being the most acidic and 14 most alkaline. The level of acidity is maintained by something called a proton pump. Since you can’t get something for nothing, the process of lowering the pH of gastric acid has a flip side: the release of bicarbonate into the bloodstream, thereby raising the pH, i.e. making it more alkaline.
Since ingesting something with an acidic residue will lower the pH of gastric acid, it makes much more sense for our bodies to down-regulate the activity of proton pumps, as opposed to leech out minerals from our bones to create alkaline substances.
Amy’s article goes into much more detail about proteins and why we under-eat them, if anything. On a different but related topic, protein consumption also has no impact on your kidneys (listen to podcast for more about that), and does not cause gout. Eat as much meat as you like.