A high dairy protein, high-calcium diet minimizes bone turnover in overweight adults during weight loss.

A high dairy protein, high-calcium diet minimizes bone turnover in overweight
adults during weight loss.

Bowen J, Noakes M, Clifton PM.

CSIRO Health Sciences and Nutrition, Adelaide, South Australia, Australia,
5000.

Weight loss induces bone resorption and this can be attenuated by calcium
supplementation. Protein-rich diets were recently associated with favorable
effects on bone density, although this remains controversial. We
hypothesized that a diet high in calcium and protein would minimize bone
resorption during weight loss compared with a lower calcium, protein-rich
diet. The effects of dietary calcium in high protein diets on calcium excretion
and bone metabolism were examined in overweight adults (n = 50, BMI 33.4
+/- 2.1 kg/m(2)) during 12 wk of energy restriction followed by 4 wk of energy
balance. Subjects were randomly assigned to isoenergetic diets (5.5 MJ/d,
34% energy from protein, 41% carbohydrate, 24% fat) high in either dairy
protein (DP, 2400 mg Ca/d) or mixed protein sources (MP, 500 mg Ca/d).
During energy restriction, weight loss was 10% (-9.7 +/- 3.8 kg, P 0.01), and
24-h urinary calcium excretion decreased independently of diet (-1.09 +/- 0.23
mmol/d, P 0.01). By wk 16, the MP diet group had a 40% greater increase in
deoxypyridinoline (bone resorption marker) than the DP diet group (P =
0.008). Osteocalcin (bone formation marker) increased from wk 0 to 16 in only
the MP diet group [+2.16 +/- 0.63 micro g/L (+0.63 +/- 0.11nmol/L), P = 0.001].
In conclusion, weight loss was associated with increased bone resorption,
yet the DP diet had a modest advantage over the MP diet by minimizing
overall turnover. Combined with reduced urinary calcium excretion, this
suggests that a high-protein, calcium-replete diet may protect against bone
loss during weight reduction.