Since Atkins resurfaced as a so-called craze in the late 1990s, both the Atkins approach and low carb diets generally have been on the receiving end of some extremely bad press. In 2001, the American Heart Association Nutrition Committee came right out with it:
"Individuals who follow these [high-protein] diets are at risk for...potential cardiac, renal, bone, and liver abnormalities overall."
From a personal perspective, I've never felt healthier than while following a low carb plan. My
hair is shiny, and my skin has cleared up incredibly. My nails are
strong and grow at lightning speed (as does my hair...I think it's all
the protein). My bad knee (botched surgery) swells up far less and
joint pain has decreased significantly.
I used to get sick two or three times every winter. I'd always
catch a decent percentage of all the bugs going round. Since I started
low carbing three years ago, I've been sick twice. That includes colds.
I've also lost over 30 lbs, dropping my BMI from a whopping 29.5 (just .5 away from being officially classified as obese), down to 24.8 (sneaking in at the high end of normal).
But hey, any chump can witter on about shiny hair and a less chunky rump. On to the scientists!
In a paper published in the Sports Nutrition Review Journal in May 2004, Anssi H. Manninen of the Department of Physiology, University of Oulu, Finland, sets out to test the claims of the American Heart Association.
What follows is a summary of this paper. To read the original, scroll down for the link.
THE CLAIM: Increasing the amount of protein consumed above the recommended daily allowance will put excessive strain on the kidneys, causing kidney stones and eventually, kidney disease.
THE TRUTH:
1) There is no data to demonstrate that a healthy kidney will be damaged by increasing protein intake.
2) Kidney problems are rare to nonexistent in the bodybuilding community, in which high-protein intake has been typical for over fifty years.
3) From a comprehensive review on protein intake and renal function: "it is clear that protein restriction does not prevent 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 reason to restrict protein intake in healthy individuals in order to protect the kidney."
THE CLAIM: Increasing dietary protein increase urine calcium excretion. It follows that the higher the protein intake, the more urine calcium is lost and the more negative calcium balance becomes. High protein diets would result in increased prevalence of ostepenia or osteoporotic-related fractures.
THE TRUTH:
1) A recent trail found no significant differences in mean urinary calcium excretion when comparing samples from graded levels of dietary protein.
2) Dietary protein increases circulating IGF-1, a growth factor thought to play an important role in bone formation.
3) 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. He concluded that the balance of the evidence seems to indicate the opposite.
THE CLAIM: High protein intake may increase blood pressure.
THE TRUTH:
A negative correlation has been shown between protein intake and systolic and diastolic blood pressures.
THE CLAIM: High protein intake may have detrimental effects on liver function.
THE TRUTH:
1) There is no scientific evidence supporting this contention.
2) Protein is needed not only to promote liver tissue repair, but also to provide lipotropic agents for the conversion of fats to lipoprotein for removal from the liver, thus preventing fatty infiltration.
THE CLAIM: 100g of carbohydrates per day is the minimum requirement to prevent loss of lean muscle tissue. (Also heard as: You're only losing muscle!)
THE TRUTH:
1) Catabolism of lean body mass is reduced by ketones, which likely explains the preservation of lean tissue observed during very-low-carbohydrate diets.
2) A study following subjects on a carbohydrate-restricted diet (8% carbohydrate) for six weeks found that fat mass was significantly decreased (-3.4kg) and lean body mass significantly increased (+1.1kg). The control group (48% carbohydrate) showed no significant changes in body composition.
ADDITIONAL ADVANTAGES FOR DISEASE PREVENTION AND/OR MANAGEMENT:
Diabetes
The metabolic effects of a high-protein diet were compared to those of the prototypical diet currently recommended to people with Type 2 diabetes. The authors concluded that the high-protein diet lowers blood glucose after meals in Type 2 diabetics, and improves overall glucose control.
Heart Disease
Recent findings suggest that replacing carbohydrates with protein may be associated with a lower risk of ischemic heart disease.
The full paper, including specific numbers from all studies, may be found here:
High-Protein Weight Loss Diets and Purported Adverse Effects: Where is the Evidence?
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