Calcium mechanism for weight loss
gets clinical support
February 25, 2005
Calcium could reduce body weight by binding fat in
the intestine and increasing its excretion from the
body, say Danish researchers, who have provided the
first clinical evidence to support a mechanism for the
weight loss effect of dairy produce.
Several epidemiological studies in recent years have
showed an inverse relationship between calcium intake
and body weight. In 2002, a US team reported that a
high calcium diet resulted in greater weight and fat
loss in obese adults on a low-calorie diet than in those
on a low calcium diet.
Researchers have suggested some possible mechanisms
for this effect but there has been little evidence so
far to support the observational findings.
The new study, published in the March issue of the
International Journal of Obesity (vol 29, no 3, pp 292-301),
shows that fat excreted in the faeces increased 2.5-fold
in people on a high calcium diet compared with when
they lowered their calcium intake.
Lead author Professor Arne Astrup at the Royal Veterinary
and Agricultural University in Denmark says that this
mechanism could be enough to explain a 4kg drop in weight
over a year.
“I had this hypothesis that calcium could bind
fat in the GI tract and had to find out if it could
affect weight through faecal fat excretion. But it surprised
us that it was so much,” he told NutraIngredients.com.
A short-term boost in dietary calcium increased faecal
fat and energy excretion by around 350 kJ per day.
“This is a very solid finding and seen across
all of the subjects,” added Professor Astrup.
The researchers set up a trial that tightly controlled
the diets and energy expenditure of 10 healthy, moderately
overweight volunteers. The randomized crossover study
tested three diets with different calcium and protein
levels, mainly from low-fat dairy products.
These were low calcium (500mg) and normal protein (making
up 15 per cent of energy), high calcium (1800mg) and
normal protein and high calcium and high protein (23
per cent of energy).
Calcium intake had no effect on 24-hour energy excretion
or fat oxidation, ruling out one previously suggested
mechanism that the mineral could affect the mineral’s
role in fat metabolism by influencing fat's oxidation.
However faecal fat excretion came to 14.2g per day
for the high calcium, normal protein diet, compared
to 6g for the low calcium diet and 5.9g for the low
calcium, high protein diet.
The high calcium diet also increased faecal energy
excretion as compared with the other diets.
There were no effects on blood cholesterol, free fatty
acids, triacylglycerol, insulin, leptin, or thyroid
hormones.
The findings are important because this is the first
human intervention study to support calcium’s
fat-binding mechanism through consumption of dairy products.
“The mechanism by which calcium increases fat
excretion is probably an interaction between calcium
and fatty acids, resulting in the formation of insoluble
calcium fatty acid soaps and hence in reduced fat absorption,”
write the authors.
Professor Astrup noted: “We now have a very good
explanation for this effect on weight but there may
be others. There could be an effect of calcium on appetite
but we wouldn’t have seen it as we controlled
energy intake among the subjects.”
Astrup’s team has begun working on further human
trials to test the mechanisms of calcium on weight.
The study does not explain the differences seen previously
between dairy products and a lower effect from supplements.
Source:www.nutraingredients.com
|
