A common misconception is that high-protein diets compromise bone health. 31 studies found a small, but significant benefit from greater protein intake on bone health. In addition, high-protein diets were associated with more bone mineral density in several skeletal sites including the lumbar spine in every category of the population, from children to elderly men and women. We also know that eating more protein increases levels of insulin-like growth factor 1, calcium absorption, and muscle strength, all of which benefit the skeleton.
The argument that high-protein diets compromise bone strength comes from the theory that high-protein diets cause an excess acid load, which the body needs to neutralize. Some scientists theorize the body neutralizes the acid by releasing bicarbonate ions from the bone matrix, a mechanism that is accompanied by a loss of sodium, calcium, and potassium, hence the extra calcium in the urine. The excess acid load also is thought to decrease bone-building activity and increase bone loss.
It is true that an excess acid load, which is defined as having a lower pH in the body – below seven, is linked with bone loss and poor health in general. Eating a high-protein diet hasn’t been proven to cause this. This may be due to the fact that diets high in animal protein contain a lot of phosphorus, which stops the calcium loss in the urine. Purified protein sources such as casein, lactalbumin, wheat gluten, and dried white eggs don’t have the same level of phosphorous, and they do lead to greater calcium loss in the urine and a lower pH. This is likely where the misconception originated.
With that knowledge, it seems that there are various mechanisms that work together, as well as against each other, to make a high protein load result in better bone health. On the negative side, there’s the tendency of high-protein diets to be more acid forming which results in the loss of calcium in the urine.
On the plus side, a high-protein diet strengthens bones by numerous mechanisms. High-protein diets provide more vitamin-D, for instance. There are several studies showing that those with higher serum vitamin-D levels have less risk of bone fracture.
Dietary protein also results in greater production and action of IGF-1, a hormone that is a major role player in bone metabolism and also activates bone building. In animal studies low-protein diets have been shown to decrease IGF-1, leading to bone loss. This effect was reversed with amino acid supplementation, which resulted in greater IGF-1 levels and subsequent bone building.
Bone building requires a pool of amino acids in the body, and believe it or not, over 50 percent of bone is made of protein. Greater muscle mass, strength, and bone mass are all correlated with protein intake. It’s well known that higher protein intake alone can help maintain muscle mass as we age.
The real concern for maintaining bone health regardless of protein intake, is the acid/base balance in the body. When not in proper balance it has been shown to lead to bone and muscle loss, poor kidney function, slow metabolism and fat gain, high cortisol, and ultimately, cancer.
The key to getting the best results with a high-protein diet is to eat foods that will counter the acid from protein. Although high-protein foods are acidic, eating them leads the body to excrete that acid more effectively, lowering your acid load.
You can offset your protein acid load by eating fruits and vegetables, especially dark green vegetables. Spinach, kale, zucchini, lettuce, leeks, broccoli, and root vegetables are all very alkaline. Eliminate all processed grains and minimize whole grain intake because these produce acid as well. Cheese is one of the most acid-producing foods and should be limited, as should dairy intake. Taking glutamine has been shown to neutralize acid in the body. Drink mineral water or add lime to water to make it more alkaline and decrease your acid load. Ensure you get adequate vitamin-D and magnesium because both are necessary for bone building and they enable calcium to be absorbed and used by the body. Functional practitioners typically recommend 5,000 IU’s of vitamin-D and 500 milligrams of magnesium a day.