Meat and soy proteins equal role in calcium absorption
have on the bone health finds that calcium absorption from these
two important sources of dietary protein is similar.
Previous studies have held that high protein diets increase urinary excretion of the mineral calcium, known to be essential to bone health.
This latest research, at US government laboratories, compared animal protein and vegetable protein diets.
The scientists at the Agricultural Research Service report they found "no indications of differences in calcium or bone metabolism" after eating either diet.
"Moreover, the soy-protein-substituted diet did not change the absorption or excretion of calcium" say the researchers.
Protein ingredients are used in a wide variety of foods. On the back of the burgeoning functional food trend, suppliers of soy proteins, with over 76 per cent of the market, currently dominate the plant protein sector.
"The plant protein segment is the fastest growing sector, reflecting the impact of increasing consumer concerns over animal related diseases and other health concerns and their impact on animal proteins," say market analysts Independent Equity Research.
But animal proteins still dominate the global $10 billion (€7.6bn) protein ingredient market, with an estimated 53 per cent share.
Publishing their findings in the January issue of The Journal of Clinical Endocrinology & Metabolism, the ARS scientists controlled the diets of 13 healthy, postmenopausal women. Two seven-week experimental diets were provided to each of the volunteers: a two week break was slotted in between each of the two diet phases.
Both diets provided 15 per cent of energy - or daily caloric intake - from protein, a percentage that, according to the researchers, represents average US consumption.
One diet contained mostly meat protein, and the other substituted 25 grams of high-isoflavone soy protein for an equivalent amount of the meat protein provided daily. The remainder of each diet was mixed to represent typical daily intakes of calcium and other nutrients.
They measured biomarkers in blood and urine collected during two seven-week diet phases. "Some scientists long have theorised that high-meat protein diets can leach calcium from bones. Others theorise that the phytate, a component of soy protein, can interrupt mineral absorption in general," say the scientists.
But they conclude from their findings that calcium absorption from both dietary protein sources is "similar".
Research published last year found that high protein diets may in fact boost bone health, again contradicting fears by nutritionists that increasing protein intake could lead to calcium losses.
High protein have been the source of much criticism from the nutrition community but while many nutritionists agree that the diet may not be nutritionally balanced, the new study suggests that protein may decrease bone resorption, a process that make bones stronger.
"In contrast to the widely held belief that increased protein intake results in calcium wasting, meat supplements, when exchanged isocalorically for carbohydrates, may have a favourable impact on the skeleton in healthy older men and women," write the researchers.
Their findings, published in the March issue of the Journal of Clinical Endocrinology & Metabolism (89:1169-1173), were drawn from a study on 32 men and women over 50; who were randomised to either a high or low protein intake diet for nine weeks, and who were already including the recommended 800 milligrams of calcium in their diet.
