Monthly Archives: December 2013

Animal Protein Associated with Decreased Ultrasound Bone Measurement in Women – 2005

Abstract

The relation between dietary protein, calcium and bone health in women: results from the EPIC-Potsdam cohort.

The role of dietary protein in bone health is controversial. The objective of the present study was to examine the association between protein intake, dietary calcium, and bone structure measured by broadband ultrasound attenuation (BUA).
Our analysis includes 8,178 female study participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) Potsdam Study. Ultrasound bone measurements were performed on the right os calcis, and BUA was determined. Dietary intake was assessed by a standardized food frequency questionnaire. We applied linear regression models to estimate the association between dietary protein and BUA.
After multivariate adjustment, high intake of animal protein was associated with decreased BUA values (beta = -0.03; p = 0.010) whereas high vegetable protein intake was related to an increased BUA (beta = 0.11; p = 0.007). The effect of dietary animal protein on BUA was modified by calcium intake.
High consumption of protein from animal origin may be unfavourable, whereas a higher vegetable protein intake may be beneficial for bone health. Our results strengthen the hypothesis that high calcium intake combined with adequate protein intake based on a high ratio of vegetable to animal protein may be protective against osteoporosis.

Weikert C, Walter D, Hoffmann K, Kroke A…
Ann. Nutr. Metab. Sep-Oct 2005
PMID: 16088096 | Free Full Text

Protein Sulfur Associated with Lower Bone Density in Postmenopausal Women – 2008

Abstract

A positive association of lumbar spine bone mineral density with dietary protein is suppressed by a negative association with protein sulfur.

Dietary protein is theorized to hold both anabolic effects on bone and demineralizing effects mediated by the diet acid load of sulfate derived from methionine and cysteine. The relative importance of these effects is unknown but relevant to osteoporosis prevention. Postmenopausal women (n = 161, 67.9 +/- 6.0 y) were assessed for areal bone mineral density (aBMD) of lumbar spine (LS) and total hip (TH) using dual X-ray absorptiometry, and dietary intakes of protein, sulfur-containing amino acids, and minerals using a USDA multiple-pass 24-h recall. The acidifying influence of the diet was estimated using the ratio of protein:potassium intake, the potential renal acid load (PRAL), and intake of sulfate equivalents from protein. aBMD was regressed onto protein intake then protein was controlled for estimated dietary acid load. A step-down procedure assessed potential confounding influences (weight, age, physical activity, and calcium and vitamin D intakes). Protein alone did not predict LS aBMD (P = 0.81); however, after accounting for a negative effect of sulfate (beta = -0.28; P < 0.01), the direct effect of protein intake was positive (beta = 0.22; P = 0.04). At the TH, protein intake predicted aBMD (beta = 0.18; P = 0.03), but R2 did not improve with adjustment for sulfate (P = 0.83). PRAL and the protein:potassium ratio were not significant predictors of aBMD. Results suggest that protein intake is positively associated with aBMD, but benefit at the LS is offset by a negative impact of the protein sulfur acid load. If validated experimentally, these findings harmonize conflicting theories on the role of dietary protein in bone health.

Thorpe M, Mojtahedi MC, Chapman-Novakofski K, McAuley E…
J. Nutr. Jan 2008
PMID: 18156408 | Free Full Text

Animal Protein Increases Bone Loss and Fracture in Postmenopausal Women – 2001

Abstract

A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. Study of Osteoporotic Fractures Research Group.

Different sources of dietary protein may have different effects on bone metabolism. Animal foods provide predominantly acid precursors, whereas protein in vegetable foods is accompanied by base precursors not found in animal foods. Imbalance between dietary acid and base precursors leads to a chronic net dietary acid load that may have adverse consequences on bone. We wanted to test the hypothesis that a high dietary ratio of animal to vegetable foods, quantified by protein content, increases bone loss and the risk of fracture. This was a prospective cohort study with a mean (+/-SD) of 7.0+/-1.5 y of follow-up of 1035 community-dwelling white women aged >65 y. Protein intake was measured by using a food-frequency questionnaire and bone mineral density was measured by dual-energy X-ray absorptiometry. Bone mineral density was not significantly associated with the ratio of animal to vegetable protein intake. Women with a high ratio had a higher rate of bone loss at the femoral neck than did those with a low ratio (P = 0.02) and a greater risk of hip fracture (relative risk = 3.7, P = 0.04). These associations were unaffected by adjustment for age, weight, estrogen use, tobacco use, exercise, total calcium intake, and total protein intake. Elderly women with a high dietary ratio of animal to vegetable protein intake have more rapid femoral neck bone loss and a greater risk of hip fracture than do those with a low ratio. This suggests that an increase in vegetable protein intake and a decrease in animal protein intake may decrease bone loss and the risk of hip fracture. This possibility should be confirmed in other prospective studies and tested in a randomized trial.

Sellmeyer DE, Stone KL, Sebastian A, Cummings SR
Am. J. Clin. Nutr. Jan 2001
PMID: 11124760 | Free Full Text

More recent studies and randomized trials have discredited the conclusions of this study.

There are two published comments on this study. The full text is available for both.

Protein intake and bone health: the influence of belief systems on the conduct of nutritional science.
Heaney RP
PMID: 11124741 | Free Full Text

Dietary ratio of animal to vegetable protein and rate of bone loss and risk of fracture in postmenopausal women.
Sebastian A, Sellmeyer DE, Stone KL, Cummings SR
Am. J. Clin. Nutr. Sep 2001
PMID: 11522569 | Free Full Text