High-protein diets, like the popular Dr
Dukan diet, increase the long-term risk of developing kidney disease and have a
negative effect on renal urinary and morphological markers.
What's more, they
may promote serious pathologies like nephrolithiasis (calcium kidney stones)
because they drastically reduce urinary citrate (an inhibitor of calcium salt
crystallization) and urinary pH, and increase urinary calcium (to compensate
for the metabolic acidity caused by excess protein).
University of Granada scientists have
proved this in an experiment in rats that examined the effects of a
high-protein diet on renal urinary, plasma and morphological parameters.
Read: The Atkins diet
The researchers studied 20 Wistar rats,
divided into two groups of 10. The first group were fed a high-protein diet of
commercial hydrolysed protein supplements with a 45% protein level. The control
group were fed a normal protein diet. The experiment lasted 12 weeks, which is
the equivalent of 9 years in human terms.
The results showed that the rats on a
high-protein diet lost up to 10% of their body weight over the 12 weeks with no
improvement in their plasma lipid profile.
Moreover, urinary citrate in these
rats was 88% lower and urinary pH was 15% more acidic. In the animals fed a
high-protein diet, kidney weight increased by 22%, glomerular area – the network
of capillaries that filter blood in the kidneys – by 13%, and the mesangium – a
collagen structure surrounded by these capillaries –by 32%.
Read: The Paleo diet
Serious long-term effects
The results of this study lead the
principle author, Dr Virginia A Aparicio of the University of Granada
Department of Physiology, to stress the need to closely monitor anyone on a
high-protein diet. The Dukan diet, and others like it, can have serious
long-term adverse effects on their health.
She warns that the negative effects of
high-protein diets on the kidney also depend on the presence of other nutrients
in the diet.
Read: The Tim Noakes diet
“Eating large amounts of fruit and vegetables reduces the risk of
kidney stones forming – probably due to their high potassium and magnesium
content, which compensates for the acidity of the high-protein diet," Dr
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