Eating Fat, Staying Lean
What do you think? Is a "meatier, cheesier, high-fat, low-carbohydrate spread" better for health? While I think low-carb diets are effective for weight loss in the short term, I don't believe they are healthful in the long term.
A low-carbohydrate diet is, by default, a high-protein diet (as well as a high-fat diet). That protein, often from animal foods, may cause problems.
High-protein diets make demands on the liver and kidneys, which have to work harder to get rid of the extra nitrogen. Ammonia, the nitrogen compound produced after proteins are deaminated, is toxic in even small amounts (it raises blood pH). So ammonia is combined in the liver with carbon dioxide to make the less-toxic urea. Urea is then sent to the kidneys for excretion.
People with diabetes, kidney disease, and high blood pressure can have compromised kidneys which, when presented with excess urea from high-protein diets, may fail to adequately dispose of it. They often have elevated blood urea nitrogen (BUN) levels.
Remember this study I blogged about? It found elevated BUN not just in people with compromised kidneys ... but in healthy young men fed a high-protein diet:
Effect Of Short-Term High-Protein Compared With Normal-Protein Diets On Renal Hemodynamics And Associated Variables In Healthy Young Men, American Journal of Clinical Nutrition, December 2009
"The glomerular filtration rate, filtration fraction ... blood urea nitrogen, serum uric acid, glucagon, natriuresis, urinary albumin (protein in the urine), and urea excretion increased significantly with the high-protein diet.A more recent and longer term study found kidney damage in pigs fed a high-protein diet:
Conclusions: A short-term high-protein diet alters renal hemodynamics and renal excretion of uric acid, sodium, and albumin. More attention should be paid to the potential adverse renal effects of high-protein diets."
Long-Term High Intake of Whole Proteins Results in Renal Damage in Pigs, Journal of Nutrition, September 2010
"The [high protein] compared with [normal protein] diet resulted in enlarged kidneys at both 4 and 8 months. Renal and glomerular volumes were 60–70% higher by the end of the study. These enlarged kidneys had greater evidence of histological damage, with 55% more fibrosis and 30% more glomerulosclerosis. Renal monocyte chemoattractant protein-1 levels also were 22% higher in pigs given the HP diet. Plasma homocysteine levels were higher in the HP pigs at 4 mo and continued to be elevated by 35% at 8 mo of feeding.The pigs on the high-protein diet were getting 35% of their calories from protein (as opposed to 15%), primarily egg and dairy protein.
These findings suggest that long-term intakes of protein at the upper limit of the AMDR* from whole protein sources may compromise renal health."
* Acceptable macronutrient distribution range
Unfortunately, many people don't know they have diabetes, kidney disease, or high blood pressure because all are silent in the early stages. Eating a high-protein diet with any of these conditions may accelerate organ failure. Even Loren Cordain, author of the Paleo Diet concedes this.1
If you're not young and healthy and would like to experiment with a low-carb diet, it would be sensible to get your serum creatinine and urinary protein, as well as blood glucose and blood pressure, checked periodically.