We all heard high protein diets are bad. It damages the kidneys, liver, is the contributing factor to heart disease and osteoporosis.
Many think a high protein diet is unhealthy. We'll its time to dispel these protein myths. I'll keep this short and sweet and to the point, so let's begin.
First let's discuss the importance of protein. Protein is composed of amino acids, some of which our bodies cannot produce, deeming them essential amino acids.
The adult body can produce twelve out of the twenty amino acids, the essential amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Protein is essential for building and maintaining muscles, as well as repairing the muscle damage that occurs during training.
Protein is also needed to make red blood cells, boost your immune system, produce hormones, and help keep hair, fingernails, and skin healthy.
Female athletes who eat a protein poor diet may also stop having periods1. Therefore, a higher than normal intake of protein is needed to provide the amino acids necessary for repair and recovery.
High protein rich diets are responsible for increasing calcium excretion. Thus, allegations of a protein rich diet will contribute to the onset of osteoporosis.
Many of the studies that support calcium loss due to a protein rich diet are flawed and can be debated. Recent studies actually show the opposite. Dietary protein, may not in fact cause an increased in calcium excretion and that it may potentially improve bone mass2.
Other studies actually suggest a positive relation between protein intake and bone mineral density3,4. A protein poor diet causes less calcium to be excreted, but also decreases calcium absorption5. Thus, the decrease in calcium is due to a reduction in protein intake.
The notion of a high protein diet negatively affecting the liver is ridiculous. Amino acids are the primary fuel source for the liver. Protein is needed to repair liver tissue and aid in the conversion of fats to lipoproteins so that they may be removed from the liver6.
The kidneys are involved in nitrogen excretion, and thus said that a high nitrogen intake (protein) may stress the kidneys. Studies examining kidney function comparing bodybuilders and athletes consuming moderate protein intake showed no differences in kidney function7.
Scientific literature showed that a low protein intake may actually be the major cause of the renal decline8. That being said, a high protein diet has been shown to improve liver function in alcoholic liver disease, and recently being looked at in treatment for liver disease9,10.
There's no evidence supporting that a high protein intake will have any negative affects on the heart. Evidence suggests that protein intake is actually beneficial in the prevention of heart disease11.
The production of free radicals are more pronounced in the metabolism of carbohydrates or fat in comparison to protein12, increased levels are thought to accelerate atherosclerosis a major contributor to heart disease.
Studies suggest that a higher protein to carbohydrates ratio may reduce the risk of Coronary Artery Disease, by decreasing triglyceride levels and increasing HDL (good) cholesterol levels13,14.
Does a protein rich diet seem unhealthy? After allegations of a high protein intake being the cause of liver and kidney damage, heart disease and induced osteoporosis. Portraying a protein rich diet as a negative, when looked at more closely a protein rich diet is actually beneficial and more of a friend than portrayed as a foe.
1. Nelson ME, Fisher EC, Catsos P, et al: Diet and bone status in amenorrheic runners. Am J Clin Nutr 1986;43(6): 910-916
2. Dawson-Hughes B, Harris SS, Rasmussen H et al. Effect of dietary protein supplements on calcium excretion in healthy older men and women. J Clin Endocrinol Metab 2004;89:1169-73.
3. Geinoz G, Rapin CH, Rizzoli R et al. Relationship between bone mineral density and dietary intakes in the elderly. Osteoporos Int 1993;3:242-8.
4. Cooper C, Atkinson EJ, Hensrud DD et al. Dietary protein intake and bone mass in women. Calcif Tissue Int 1996;58:320-325.
5. Kerstetter JE, Svastislee C, Caseria D et al. A threshold for low-protein-diet-induced elevations in parathyroid hormone. Am J Clin Nutr 2000;72:168-173.
6. Navder KP, Lieber CS. Nutrition and alcoholism. In: Bronner, F. ed. Nutritional Aspects and Clinical Management of ChronicDisorders and Diseases. Boca Raton, FL: CRC Press, 2003, pp. 307-320
7. Poortmans JR, Dellalieux O. Do regular high-protein diets have potential health risks on kidney function in athletes? Int J Sports Nutr 2000;10:28-38.
8. Walser M. Effects of protein intake on renal function and on the development of renal disease. In: The Role of Protein and Amino Acids in Sustaining and Enhancing Performance. Committee on Military Nutrition Research, Institute of Medicine. Washington, DC: National Academies Press, 1999, pp. 137-154.
9. Mendellhall C, Moritz T, Roselle GA et al. A study of oral nutrition support with oxadrolone in malnourished patients with alcoholic hepatitis: results of a Department of Veterans Affairs Cooperative Study. Hepatology 1993;17:564-576.
10. Suzuki K, Kato A, Iwai M. Branched-chain amino acid treatment in patients with liver cirrhosis. Hepatol Res. 2004 Dec;30S:25-29.
11. Hu FB, Stampfer MJ, Manson JE, et al. Dietary protein and risk of ischemic heart disease in women. Am J Clin Nutr 1999; 70:221-7.
12. Mohanty P, Ghanim H, Hamouda W et al. Both lipid and protein intake stimulates increased generation of reactive oxygen species by polymorphonuclear leukocytes and mononuclear cells. Am J Clin Nutr 2002;75:767-772.
13. Hu FB, Stampfer MJ, Manson JA et al. Dietary protein and risk of ischemic heart disease in women. Am J Clin Nutr 1999;70:221-227.
14. Layman DK, Boileau RA, Erickson DJ, Painter JE, Shiue H, Sather C, Christou DD. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr. 2003 Feb;133(2):411-7.
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