WARNING: Sciency Article.
Many popular diets are higher in protein and many people suggest eating more, but is it safe? You can read about the benefits of a high protein intake and my recommendations for protein intake here: How Much Protein Do You Need? But even with all these benefits, could there be some harm? Dietitians and doctors alike often claim that a high protein diet is bad for the kidneys and for a variety of other reasons. Some of these concerns are real and some have no real proof to support them. Below I will state some common health concerns with higher protein intake on health and comment on each:
Reason 1. Increased stress on kidneys because of increases in filtration rate.
This is probably the most common and significant concern that I hear about increasing protein intake. Higher protein diets in patients with Chronic Kidney Disease cause kidney function to decline at a faster rate than consuming less protein. Therefore, people think that high protein diets may cause healthy kidneys to decline in function. This belief comes from studies that prove that kidney filtration increases when you eat more protein. They think that the increased rate of filtration is bad for the kidney.
However, there is absolutely no evidence that higher protein intakes can cause people with healthy kidneys to develop Chronic Kidney Disease. None. Zero. High protein diet studies conducted for up to 6 months have not shown a decline in kidney function. The rate of kidney filtration increases during pregnancy and during removal of a kidney as an adaptation to compensate for the lost kidney just like it does when eating a higher protein diet. Pregnancy and kidney removal are not risk factors for developing Chronic Kidney Disease, so why should we just assume that high protein diets are a risk factor when there is no further evidence? Based on this evidence that increased kidney filtration rates do not necessarily cause a faster decline in kidney function and the lack of evidence behind high protein intake causing a decline in the function of healthy kidneys, the argument that high protein intakes are bad for healthy kidneys is unsubstantiated and purely speculative. More research is needed in this field (long-term studies comparing a high protein diet to a standard diet that observe kidney function).
See this study here.
Reason 2. Increased calcium excretion and negative effects on bone mineral density.
If you eat adequate calcium (RDA 1000-1200 mg), then protein actually has a positive effect on bone health and promotes higher bone mineral density. If eating too little calcium, high protein diets may have a negative effect on bone mineral density.
Reason 3. Decreased blood pH, leading to low grade metabolic acidosis.
Eating adequate fruits and vegetables neutralize the acid from the protein and negate this potential negative effect. Potassium to protein ratio is a better indicator for how diet alters acid-base balance in the body.
Reason 4. Increased risk for chronic disease like cancer and heart disease (mostly an accusation made towards increasing protein by eating more red and processed meats).
Epidemiological research (correlational rather than causational) shows that people that eat large amounts of red and processed meat get cancer, particularly colorectal cancer, more often even when variables like exercise, smoking, and other factors were controlled for. This increased rate of cancer is likely because of compounds that increase when red meat is cooked and nitrates that are added to processed meats. There are ways to decrease the harmful compounds in red meat that can be found here. Decreasing the harmful compounds in red meat can be summarized as marinade it, don’t burn it, be sure to eat your fruits and vegetables with it, and minimize the processed meats with added nitrates.
The World Cancer Research Fund recommends limiting red meat to a total of 500 grams (1 lb 1 oz) of cooked red meat per week. Using the methods above to decrease the harmful compounds in these red meats likely gives you some wiggle room to eat a little more red meat than this recommendation without increasing your risk for cancer.
High protein diets are likely safe if eaten with plenty of fruits and vegetables to offset acidosis and adequate calcium (1000-1200 mg/day) to benefit bone health. Try to eat at least 5 servings of vegetables (1 servings = 1 cup raw vegetables or ½ cup cooked), 4 servings of fruit (1 serving=1/2 cup), and 3 servings of dairy (1 serving= 1 cup milk, 1 cup yogurt, ½ cup cottage cheese, 1.5 oz hard cheese) when eating a high protein diet to negate potential negative effects on bone health and from metabolic acidosis.
What Matters in this Blog Post
1. High protein diets confer some benefits found here: How Much Protein Do You Need?
2. No proof exists that high protein diets are bad for healthy kidneys.
3. Protein improves bone health when enough calcium is consumed, but hurts bone health if not enough calcium is consumed.
4. Protein won’t cause acidosis if adequate fruits and vegetables are consumed.
5. Eat less than 500 g (1 lb 1 oz) of red meat per week. Avoid processed meats with added nitrates. Ways to decrease harmful compounds in red meat and possibly allow you to eat a little more red meat can be found here.
6. Eating more protein as a part of a balanced diet is very likely safe. There is no reason to assume otherwise.