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Claim Number 1:
High Protein Diets Are Bad For Bone Health
Investigation: At one time or another you have probably heard the claim that "high protein diets are bad for your bones, and they cause calcium losses." However, when examining the scientific evidence we see a different picture.
A large study published in the Journal of Bone and Mineral Research showed that both elderly men and women who consumed the most animal protein had the lowest rate of bone loss whereas those who consumed little protein had much higher rates of bone loss.
A study published in the American Journal of Clinical Nutrition has shown that postmenopausal women who consumed the highest amount of protein, particularly animal protein, were least likely to suffer from hip fractures and had the strongest bones.1
Heaney and colleagues showed, that in free-living middle-aged women who were studied in a metabolic ward and ingested diets that matched their everyday intakes of protein and phosphorus, calcium losses were significantly positively correlated with protein intake and calcium balance was significantly negatively correlated.2
This study, cited extensively since its publication, contributed to the common belief that protein is harmful to bone. Almost two decades later in an editorial that was featured in the American Journal of Clinical Nutrition, Heaney critiqued his own study and reported on recent findings.3
In conclusion Heaney stated, "Analysis of the diets of hunter-gatherer societies, and nitrogen isotope ratios of fossil bone collagen, indicate that human physiology evolved in the context of diets with high amounts of animal protein.
Although caution has been urged in the interpretation of such analyses, it remains true that there is certainly no evidence that primitive humans had low intakes of either total protein or animal protein. That, coupled with the generally very robust skeletons of our hominid forbears, makes it difficult to sustain a case, either evidential or deductive, for overall skeletal harm related either to protein intake or to animal protein. Indeed, the balance of the evidence seems to indicate the opposite."
Research suggests that consuming high protein diets that contain sufficient amounts of calcium and Vitamin D do not negatively affect bone health. Researchers at Tufts University in Boston found that adequate ingestion of dietary calcium helps to promote a positive effect of dietary protein on the skeleton in older adults. Also, phosphorus (like in milk and meat) and potassium (found in milk, legumes, and grains) reduce calcium loss, thus negating protein-induced urinary calcium excretion.
Conclusion: A high protein diet that lacks sufficient amounts of calcium and Vitamin D may cause harm to bones. But a high protein diet that contains sufficient amounts of calcium and Vitamin D can have positive affects on bone health.
Click To Enlarge.
A High Protein Diet May Cause Harm To Bones
Without Sufficient Amounts Of Calcium And Vitamin D.
Claim Number 2:
High Protein Diets Increase The Risk Of Coronary Heart Disease
Investigation: A review conducted by Li and colleagues4 looked at the relationship between red meat consumption and coronary heart disease factors; 54 studies were reviewed.
Findings of the review indicated that, "Substantial evidence from recent studies shows that lean red meat trimmed of visible fat does not raise total blood cholesterol and LDL-cholesterol levels." And also that "lean red meat is low in saturated fat, and if consumed in a diet low in SFA (saturated fatty acids), is associated with reductions in LDL-cholesterol in both healthy and hypercholesterolemia (high cholesterol) subjects."
In conclusion the studies found that "lean red meat trimmed of visible fat, which is consumed in a diet low in saturated fat does not increase cardiovascular risk factors."
Conclusion: High protein diets that contain excessive calories and high fat may increase risk factors associated with coronary heart disease. But high protein diets that are low to moderate in calories and saturated fat do not increase risk factors. I generally recommend a few servings of lean red meat each week. Red meat is loaded with micronutrients and is a good source of quality protein.
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Lean Red Meat Trimmed Of Visible Fat, Does
Not Increase Cardiovascular Risk Factors.
Claim Number 3:
High Protein Diets Are Bad For The Kidneys
Investigation: Media sources often report, "Too much protein stresses the kidney." What does science say? Martin and colleagues5 reviewed the available evidence regarding the effects of protein intake on kidney function with a particular emphasis on kidney disease.
The researchers reported, "Although excessive protein intake remains a health concern in individuals with preexisting renal disease, the literature lacks significant research demonstrating a link between protein intake and the initiation or progression of renal disease in healthy individuals."
In addition they reported, "At present, there is not sufficient proof to warrant public health directives aimed at restricting dietary protein intake in healthy adults for the purpose of preserving renal function." Protein restriction is common treatment for people with kidney problems.
I have known individuals who consume 300-400 grams of protein per day. Guess what, no kidney problems.
Conclusion: There is no evidence that high protein intake causes kidney damage in individuals with healthy kidneys. To many people this may come as a shocker.Recommended Articles
- Tbk Fitness. How to Prevent Osteoporosis. [Online] September 11, 2009 http://www.tbkfitness.org/Osteoporosis.html
- Heaney RP, et. al. Effects of nitrogen, phosphorus, and caffeine on calcium balance in women. J lab Clin Med, 99:46-55 1982.
- Heaney R. Protein intake and bone health: the influence of belief systems and the conduct of nutritional science. American Journal of Clinical Nutrition, Vol. 73,1:5-6 Jan 2001.
- Li D, et. al. Lean meat and heart health. Asia Pac J Clin Nutr, 14(2):113-9 2005.
- Martin WF, et. al. Dietary Protein intake and Renal Function. Nutrition & Metabolism 2:25 2005.
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