Two of the most common myths about high-protein diets is that they are bad for your bones and will hurt your kidneys. For healthy people neither of these are true.
In fact, evidence shows high-protein diets improve bone strength. Additionally, eating high-quality protein supports the maintenance of muscle mass as we age, which is a primary factor in bone health and the prevention of fractures related to osteoporosis.
In terms of kidney health, people with normal kidney function do not endanger their kidneys by eating a high-protein diet. For people with risk of chronic kidney disease, high-protein diets may compromise kidney function. The relationship between kidney function and large dietary protein loads is intricate, and the following review will help you understand it and make your own decisions about protein intake.
This article will dispel the myths about high-protein diets and present five dietary strategies you should use to get the best results out of a high-protein diet.
Protein Doesn’t Hurt Healthy Kidneys
The myth that eating a high-protein diet hurts the kidneys comes from the fact that in people with chronic kidney disease, eating a lot of protein can further compromise kidney function, but these are people whose kidneys already aren’t working well.
Kidneys do a variety of things in the body including filter your blood to get rid of waste, maintain proper blood pH, produce some hormones, and regulate the amount of water and sodium in the blood. The kidneys process the waste products of the food you eat including protein.
Eating large amounts of protein increases the rate at which the kidneys are filtering (called hyperfiltration), but there is no evidence that this will damage them. Rather, one research group writes that “hyperfiltration is a normal adaptive mechanism” to higher protein or biological challenges. Think of it like “training” the kidneys in the same way you train the cardiovascular or muscular system with strength training.
Studies Demonstrating Safety of High-Protein Diets
Strength and power athletes have been eating high-protein diets for years without developing kidney disease. A study from 2000 that used a mix of athletes, including cyclists, rowers, martial artists, and body builders, who were eating between 1.5 and 2 grams per kg of bodyweight of protein a day showed no evidence of impaired kidney function. The researchers concluded that daily protein intake as high 2.8 g/kg won’t damage the kidneys in healthy athletes.
Even in people who are “at risk” to suffer kidney disease, such as diabetics or the obese, a high-protein diet and elevated kidney filtration doesn’t damage the kidneys. For example, a study compared the effect of either a low-carb, high-protein diet or a low-fat weight loss diet on kidney function over two years in obese subjects.
Both diet groups lost weight, and in the high-protein diet group there was evidence of kidney hyperfiltration, but kidney function was not negatively affected in any way. Rather, kidney health was improved when the subjects lost weight because obesity by itself compromises kidney function. For example, by the end of the two-year study, the subjects had less protein in their urine, meaning the kidneys had adapted so that more of the dietary protein was absorbed and used by the body.
Pre-Existing Kidney Disease and Protein
Medical organizations discourage people with clinical kidney dysfunction or those on dialysis from eating a high protein diet.
The National Kidney Foundation has extensive recommendations for protein intake for people on dialysis. They note that these guidelines are for people on dialysis who have clinically documented kidney disease. They are not for the general population or even to serve as a prevention strategy to avoid developing kidney disease.
It’s reasonable to approach protein intake on an individualized basis rather than making blanket statements that eating a lot of protein will hurt the kidneys.
High Protein Diets and Bone Health
A common myth is that high-protein diets compromise bone health. This is not true. In fact, an analysis of 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.
Understanding The Myth
The myth that high-protein diets compromise bone strength comes from the theory that protein is acidic. 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 calcium. In practice, high-protein foods contain a lot of phosphorus, which stops the calcium. On the other hand, purified protein sources (casein, lactalbumin, wheat gluten, dried white eggs) that don’t have the phosphorous appear to lead to greater calcium loss and more acidity.
Therefore, it appears there are various mechanisms that cancel each other out from a high protein intake with the end result being better bone health.
On the negative side, there’s the tendency of high-protein diets to be more acid forming. On the positive side, a high-protein diet strengthens bones by the following mechanisms:
- High-protein diets provide more vitamin D, and studies show people with higher serum vitamin D levels have less risk of bone fracture.
- Dietary protein results in greater production of IGF-1, a hormone that is a major regulator of bone metabolism and activates bone building.
- Bone building requires a pool of amino acids in the body and 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.
Make A High-Protein Diet Healthy
By designing an individualized, balanced diet, it's possible to achieve optimal health while also having a high-protein intake. Here are tips for making it happen.
Eat the Rainbow.
Counter your protein acid load by eating lots of fruits and vegetables, especially dark green vegetables. Spinach, kale, zucchini, lettuce, leeks, broccoli, root vegetables, tomatoes, black currants, cherries, grapes, and kiwis are all fairly alkaline.
Eliminate processed grains.
Grains, especially refined ones in processed carbs, are very acid forming and should be avoided in favor of healthy carbs.
Glutamine neutralizes acid in the body.
Drink Lemon of Lime Water.
An easy way to offset the acid from protein foods is to add lemon or lime to your water. Mineral water also works.
Get Enough Vitamin D & Magnesium.
Ensure you get adequate vitamin D and magnesium because both are necessary for bone building. They also enable calcium to be absorbed and used by the body. A general recommendation is 1,000 IUs of vitamin D and 500 mg of magnesium a day.