Have you heard any of the following statements?:
“High protein diets are unhealthy.”
“High protein diets can cause kidney damage .”
“They can cause liver damage.”
“High protein diets can contribute to heart disease.”
“High protein diets have been linked to osteoporosis .”
Some scientific communities (doctors) blindly accept these claims as scripture and spread false dogma.
But are any of them true?
1. “High Protein Diets Can Damage The Kidneys”
Nitrogen is a byproduct of protein that you pee out. So it’s been theorized that eating more protein can cause additional stress to the kidneys because they have to process more nitrogen.
A lower protein diet is often prescribed to people with a high level of nitrogen in their pee. This theory is simply not backed by literature:
- This study examined bodybuilders with protein intakes of 2.8g/kg vs. well trained athletes with moderate protein intakes . It revealed no significant difference in kidney function between the groups
- This review of the scientific literature on protein intake and renal function concluded that “there is no reason to restrict protein in healthy individuals.” Furthermore, the review concluded that not only does a low protein intake NOT prevent the decline in renal function with age, it may actually be the major cause of the decline!
- The Johns Hopkins School of Medicine reviewed literature and determined “it is clear that protein restriction does not prevent the decline in renal function with age and, in fact, is the major cause of that decline. A better way to prevent the decline would be to increase protein intake.”
There is no need to restrict protein intake in healthy individuals to preserve renal function. Caveman at the gym, you just got roasted.
2. “High Protein Diet Contributes to Liver Disease”
There is NO EVIDENCE to support a high protein diet contributing to liver disease. In fact, the opposite might be true:
- Protein is needed to repair liver tissue and for the conversion of fats to lipoproteins so that they can be removed from the liver.
Amino acids are also the main fuel source for the liver.
- In alcoholic liver disease a high protein diet has been shown to improve liver function and reduce rate of death.
- BCAAs (branched chain amino acids, AKA protein) are also being investigated as a treatment for liver disease.
Research has spoken. A High protein diet DOESN’T damage the liver, and it’s been investigated as a beneficial TREATMENT!
3. “High Protein Diets Cause Bone Mineral Density Deficiencies”
Some suggest that a high protein diets can contribute to the onset of osteoperosis. This is assumed because high protein diets cause high levels of calcium excretion. The early studies are flawed because many them were limited by a low number of study participants, study design errors, and the use of the wrong types of protein.
More recent and better designed studies have shown a high protein diet:
- May actually increase bone mass [1, 2, 3, 4]
- Schurch et al. reported that supplementation with 20 g protein/day for 6 months increased blood IGF-levels and reduced the rate of bone loss in the unfractured hip during the year after the fracture.
- Low protein diets may have a detrimental effect on bone. Although calcium excretion is increased, calcium absorption in the intestines is increased.
- The author of the most cited paper favoring the earlier hypothesis that high-protein intake promotes osteoporosis no longer believes that protein is harmful to bone, but now actually believes the opposite to be true.
Even though increasing protein intake may increase calcium excretion, there isn’t any evidence this calcium comes from bone. This means overall calcium balance is either unaffected, or increased in a high protein diet.
4. “High Protein Diets Contribute To Heart Disease”
Scientific literature simply does not support high protein diets contributing to heart disease. In fact, literature argues for the opposition:
- Replacing carbohydrates with protein may be associated with a lower risk of ischemic heart disease.
- Replacing dietary carbohydrates with protein in diet improves blood lipid profile by decreasing triglycerides and increasing HDL (good) cholesterol.
- It has also been shown that diets higher in fats and carbs increases the production of free radicals (cancer contributors) in the blood at a much higher rate than a diet higher in protein.
- Free radicals and lipid peroxidation have been shown to be key contributors to the development of atherosclerosis. These are reduced in diets higher in protein.
5. Protein and Blood Pressure
The AHA Nutrition Committee suggests that high-protein intake may increase blood pressure. However, there is no scientific evidence supporting this either. Notice a pattern:
- A negative correlation has been shown between protein intake and systolic and diastolic blood pressures in several epidemiological surveys analyzed by Obarzanek et al.
- In this study of 6,406 Japanese-American men, a negative relationship was observed between systolic and diastolic blood pressures and the amount protein consumed. Meaning as protein consumption went up, blood pressure went down.
- In this investigation of 2,672 adults men and women, a negative relationship was found between systolic pressure and the amount of animal protein consumed.
- Based on 11,342 adult men, investigators observed a negative relationship between systolic blood pressure and the amount of total protein consumed.
- This study shows an inverse relationship between systolic and diastolic blood pressure when dietary carbohydrates are replaced with protein.
- One study in human volunteers with a family history of hypertension has shown that a high-protein diet may counteract the adverse effects of excessive salt intake.
6. Protein: Diabetes and Weight Loss
A high protein diet may also be beneficial for combating obesity and diabetes:
- Recent research indicates that a diet consisting of 30:40:30 (protein:carbs:fats) was superior to the food guide period diet of 15:55:30 in maintaining glucose homeostasis, increasing insulin sensitivity, and improving glucose control in normal people and those suffering from type II diabetes.
- Subjects lost more weight, higher percentage of weight loss was fat, and muscle mass was preserved better
- Investigations have shown high protein diets to be more satiating. Meaning you can diet without feeling hungry all the time.
- People who consume high protein diets tend to eat less calories, but burn more throughout the day.
It’s clear that a diet with a higher protein/carbohydrate ratio is superior in supporting better weight loss, muscle retention, glucose control, and satiety.
Protein is not detrimental to health. Studies show too many benefits of protein to limit intake in the diet of healthy (or some unhealthy) people.
What are your thoughts on protein myths? Did I miss anything you’d like covered?