Monthly Archives: September 2013

Protein Associated with Reduced Fractures

Abstract

Effects of meat consumption and vegetarian diet on risk of wrist fracture over 25 years in a cohort of peri- and postmenopausal women.

Evidence suggesting that a diet high in fruits and vegetables may be beneficial to bone health has sparked interest in the potential benefit of a vegetarian diet. However, other studies have raised a question regarding the adequacy of protein in such a diet.
The aim of the present study was to take a whole foods approach in examining the effects of foods high in protein on the risk of wrist fracture (WF) in a cohort with a significant proportion consuming a meat-free diet.
A cohort study of women who completed two lifestyle surveys 25 years apart.
One thousand eight hundred and sixty-five peri- and postmenopausal women at the time of the first survey.
There was a significant interaction between meat consumption and foods high in vegetable protein. Among vegetarians, those who consumed the least vegetable protein intake were at highest risk for fracture. However, increasing levels of plant-based high-protein foods decreased WF risk, with a 68% reduction in risk (hazard ratio (HR) = 0.32, 95% confidence interval (CI) 0.13-0.79) in the highest intake group. Among those with lowest vegetable protein consumption, increasing meat intake decreased the risk of WF, with the highest consumption decreasing risk by 80% (HR = 0.20, 95% CI 0.06-0.66).
The finding that higher consumption frequencies of foods rich in protein were associated with reduced WF supports the importance of adequate protein for bone health. The similarity in risk reduction by vegetable protein foods compared with meat intake suggests that adequate protein intake is attainable in a vegetarian diet.

Thorpe DL, Knutsen SF, Beeson WL, Rajaram S…
Public Health Nutr Jun 2008
PMID: 17686206

Review: Protein + Calcium May Benefit Bones – April 2011

Abstract

Dietary protein and bone health: harmonizing conflicting theories.

A precise understanding of the role of dietary protein in bone health has been evasive despite decades of research. It is known that a dietary acid load is harmful to bone, and sulfur-containing amino acids are metabolized to provide such an acid load. It is also known that protein elevates urine calcium loss. However, recent clinical studies and a meta-analysis have indicated either no effect or a modest benefit associated with higher protein intakes. These contradictory considerations may be explained by the existence of a two-faced relationship between protein and bone, with simultaneous positive and negative pathways. In opposition to the negative effects of dietary acid load, protein may exert positive effects related to improving calcium absorption, increasing insulin-like growth factor 1, or improving lean body mass, which, in turn, improves bone strength. Putative mechanisms behind these pathways are reviewed here, and some limitations in the historical literature as well as suggested measures to counter these in the future are identified. When positive and negative pathways are considered in tandem, protein may offer modest benefits to bone in the presence of adequate dietary calcium and acid-neutralizing fruits and vegetables.

Thorpe MP, Evans EM
Nutr. Rev. Apr 2011
PMID: 21457266

Protein and Energy Deficiencies May Increase Bone Loss in Rats – 2008

Abstract

Influence of high and low protein intakes on age-related bone loss in rats submitted to adequate or restricted energy conditions.

Low energy and protein intake has been suggested to contribute to the increased incidence of osteoporosis in the elderly. The impact of dietary protein on bone health is still a matter of debate. Therefore, we examined the effect of the modulation of protein intake under adequate or deficient energy conditions on bone status in 16-month-old male rats. The animals were randomly allocated to six groups (n = 10/group). Control animals were fed a diet providing either a normal-protein content (13%, C-NP) or a high-protein content (26%) (C-HP). The other groups received a 40% protein/energy-restricted diet (PER-NP and PER-HP) or a normal protein/energy-restricted diet (ER-NP and ER-HP). After 5 months of the experiment, protein intake (13% or 26%) did not modulate calcium retention or bone status in those rats, although a low-grade metabolic acidosis was induced with the HP diet. Both restrictions (PER and ER) decreased femoral bone mineral density and fracture load. Plasma osteocalcin and urinary deoxypyridinoline levels were lowered, suggesting a decrease in bone turnover in the PER and ER groups. Circulating insulin-like growth factor-I levels were also lowered by dietary restrictions, together with calcium retention. Adequate protein intake in the ER condition did not elicit any bone-sparing effect compared to PER rats. In conclusion, both energy and protein deficiencies may contribute to age-related bone loss. This study highlights the importance of sustaining adequate energy and protein provision to preserve skeletal integrity in the elderly.

Mardon J, Habauzit V, Trzeciakiewicz A, Davicco MJ…
Calcif. Tissue Int. May 2008
PMID: 18437274

Protein Reduces Hip Fracture with Higher Intakes in Framingham Study

Abstract

Does dietary protein reduce hip fracture risk in elders? The Framingham Osteoporosis Study.

Association between dietary protein and fracture risk is unclear. We examined association between energy-adjusted protein intake and hip fracture risk in elders. The risk of hip fracture was reduced in upper quartiles of protein intake when compared with lowest quartile.
Studies of the association between dietary protein intake and hip fracture risk are conflicting. Therefore, we examined protein intake and hip fracture risk in a population-based group of elderly men and women.
Five hundred seventy-six women and 370 men from the Framingham Osteoporosis Study with no previous history of hip fracture completed Food Frequency Questionnaires. Energy-adjusted protein intake was evaluated as a continuous variable and as quartiles. Incidence rates and hazard ratios were calculated, adjusting for age, BMI, sex, and energy intake.
Among 946 participants (mean age 75 years), mean protein intake was found to be 68 gm/d. Increased protein intake was associated with a decreased risk of hip fracture compared to those in the lowest quartile of protein intake (Q2 HR = 0.70, Q3 HR = 0.56, and Q4 HR = 0.63; all p values ≥ 0.044), p for trend was 0.07. When a threshold effect was considered (Q2-4 vs Q1), intakes in the higher quartiles combined were associated with a significantly lower risk for hip fracture (HR = 0.63; p = 0.04).
Our results are consistent with reduced risk of hip fracture with higher dietary protein intake. Larger prospective studies are needed to confirm and extend this finding in elderly men and women.

Misra D, Berry SD, Broe KE, McLean RR…
Osteoporos Int Jan 2011
PMID: 20442986

Review: Protein Recommended Intake – 2008

Abstract

Amount and type of protein influences bone health.

Many factors influence bone mass. Protein has been identified as being both detrimental and beneficial to bone health, depending on a variety of factors, including the level of protein in the diet, the protein source, calcium intake, weight loss, and the acid/base balance of the diet. This review aims to briefly describe these factors and their relation to bone health. Loss of bone mass (osteopenia) and loss of muscle mass (sarcopenia) that occur with age are closely related. Factors that affect muscle anabolism, including protein intake, also affect bone mass. Changes in bone mass, muscle mass, and strength track together over the life span. Bone health is a multifactorial musculoskeletal issue. Calcium and protein intake interact constructively to affect bone health. Intakes of both calcium and protein must be adequate to fully realize the benefit of each nutrient on bone. Optimal protein intake for bone health is likely higher than current recommended intakes, particularly in the elderly. Concerns about dietary protein increasing urinary calcium appear to be offset by increases in absorption. Likewise, concerns about the impact of protein on acid production appear to be minor compared with the alkalinizing effects of fruits and vegetables. Perhaps more concern should be focused on increasing fruit and vegetable intake rather than reducing protein sources. The issue for public health professionals is whether recommended protein intakes should be increased, given the prevalence of osteoporosis and sarcopenia.

Heaney RP, Layman DK
Am. J. Clin. Nutr. May 2008
PMID: 18469289 | Free Full Text

Protein Increases Calcium Absorption and Retention From a Low-Calcium Diet – 2009

Abstract

Dietary protein and calcium interact to influence calcium retention: a controlled feeding study.

The effect of meat protein on calcium retention at different calcium intakes is unresolved. The objective was to test the effect of dietary protein on calcium retention at low and high intakes of calcium.In a randomized controlled feeding study with a 2 x 2 factorial crossover design, healthy postmenopausal women (n = 27) consumed either approximately 675 or approximately 1510 mg Ca/d, with both low and high protein (providing 10% and 20% energy) for 7 wk each, separated by a 3-wk washout period. After 3 wk, the entire diet was extrinsically labeled with (47)Ca, and isotope retention was monitored by whole-body scintillation counting. Clinical markers of calcium and bone metabolism were measured.
High compared with low dietary protein significantly increased calcium retention from the low-calcium (29.5% compared with 26.0% absorbed) but not the high-calcium diet (18% absorbed). For the low-calcium diet, this effect nearly balanced a protein-related 0.5-mmol/d greater urinary calcium excretion. Protein-related calciuretic effects were independent of dietary calcium. Testing at 1, 2, 3, 5, and 7 wk showed no long-term adaptation in urinary acidity or urinary calcium excretion. High compared with low dietary protein decreased urinary deoxypyridinoline and increased serum insulin-like growth factor I without affecting parathyroid hormone, osteocalcin, bone-specific alkaline phosphatase, or tartrate-resistant acid phosphatase.
In healthy postmenopausal women, a moderate increase in dietary protein, from 10% to 20% of energy, slightly improved calcium absorption from a low-calcium diet, nearly compensating for a slight increase in urinary calcium excretion. Under practical dietary conditions, increased dietary protein from animal sources was not detrimental to calcium balance or short-term indicators of bone health.

Hunt JR, Johnson LK, Fariba Roughead ZK
Am. J. Clin. Nutr. May 2009
PMID: 19279077 | Free Full Text

Low Protein Increases Fractures in Women – June 2009

Abstract

Association of total calcium and dietary protein intakes with fracture risk in postmenopausal women: the 1999-2002 National Health and Nutrition Examination Survey (NHANES).

We examined the associations of total calcium intake (TCI) and dietary protein intake (DPI) with risk of fracture. A total of 2006 postmenopausal women >or=50 y of age who were measured in the 1999-2002 National Health and Nutrition Examination Survey were included in the study. Weighted mean TCI and DPI and percentage of distributions of selected characteristics were estimated by TCI category and fracture status.

Multivariate logistic regression models were used to assess the effect of TCI and DPI on risk of fracture. Thirteen percent of participants reported a fracture history, of whom 17.8% consumed a total of >or=1200 mg of calcium per day and 23.8% consumed <400 mg/d. TCI was not associated with fracture risk when controlling for all selected covariates. In women who consumed <46 g/d of dietary protein, those with a TCI >or=1200 mg/d had a significantly higher risk of fracture than those with the lowest TCI (adjusted odds ratio 5.98, 95% confidence interval 1.15-31.13), whereas in women who consumed >70 g/d of dietary protein, those with a TCI >or=1200 mg/d had an insignificant lower risk of fracture (adjusted odds ratio 0.69, 95% confidence interval 0.20-2.39).
TCI is not associated with risk of fracture among postmenopausal women. Adequate TCI in the presence of inadequate DPI may not be protective against fractures. Optimal proportion of TCI and DPI warrants further investigation among older women.

Zhong Y, Okoro CA, Balluz LS
Nutrition Jun 2009
PMID: 19230618

Review: Protein Protects Bone in Women – October 2002

Abstract

Elderly women need dietary protein to maintain bone mass.

Excess dietary protein is considered a risk factor for osteoporosis owing to the potential for renal acid load. Researchers who conducted a recent prospective study of older adults reported that animal protein had a protective role for bone, especially in elderly women, whereas plant protein was negatively associated with bone mineral density. An interaction between protein and calcium suggested protein alone was not the important factor. Other studies confirm the beneficial effect of increasing dietary protein intake in older women to reduce bone mineral density loss and risk of fracture, suggesting that emphasis should be placed on promoting adequate protein intake in elderly women.

Bell J, Whiting SJ
Nutr. Rev. Oct 2002
PMID: 12392151

Protein Associated with Reduced Hip Fracture in Women

Abstract

Prospective study of dietary protein intake and risk of hip fracture in postmenopausal women.

The role of dietary protein intake in osteoporosis remains controversial. Protein is an important structural component of bone and protein supplementation improves the medical outcome of hip fracture patients, but it is unknown whether protein intake can reduce the incidence risk of hip fracture.
The relation between intake of protein and other nutrients and subsequent incidence of hip fracture was evaluated.
Nutrient intake was assessed with a food-frequency questionnaire in a cohort of Iowa women aged 55-69 y at baseline in 1986. Incident hip fractures were ascertained through follow-up questionnaires mailed to participants in 1987 and 1989 and verified by physician reports.
Forty-four cases of incident hip fractures were included in the analyses of 104338 person-years (the number of subjects studied times the number of years of follow-up) of follow-up data. The risk of hip fracture was not related to intake of calcium or vitamin D, but was negatively associated with total protein intake. Animal rather than vegetable sources of protein appeared to account for this association. In a multivariate model with inclusion of age, body size, parity, smoking, alcohol intake, estrogen use, and physical activity, the relative risks of hip fracture decreased across increasing quartiles of intake of animal protein as follows: 1.00 (reference), 0.59 (95% CI: 0.26, 1.34), 0.63 (0.28, 1.42), and 0.31 (0.10, 0.93); P for trend = 0.037.
Intake of dietary protein, especially from animal sources, may be associated with a reduced incidence of hip fractures in postmenopausal women.

Munger RG, Cerhan JR, Chiu BC
Am. J. Clin. Nutr. Jan 1999
PMID: 9925137 | Free Full Text

Protein > 95 Grams Associated With Forearm Fracture in Women

Abstract

Protein consumption and bone fractures in women.

Dietary protein increases urinary calcium losses and has been associated with higher rates of hip fracture in cross-cultural studies. However, the relation between protein and risk of osteoporotic bone fractures among individuals has not been examined in detail. In this prospective study, usual dietary intake was measured in 1980 in a cohort of 85,900 women, aged 35-59 years, who were participants in the Nurses’ Health Study. A mailed food frequency questionnaire was used and incident hip (n = 234) and distal forearm (n = 1,628) fractures were identified by self-report during the following 12 years. Information on other factors related to osteoporosis, including obesity, use of postmenopausal estrogen, smoking, and physical activity, was collected on biennial questionnaires. Dietary measures were updated in 1984 and 1986. Protein was associated with an increased risk of forearm fracture (relative risk (RR) = 1.22, 95% confidence interval (Cl) 1.04-1.43, p for trend = 0.01) for women who consumed more than 95 g per day compared with those who consumed less than 68 g per day. A similar increase in risk was observed for animal protein, but no association was found for consumption of vegetable protein. Women who consumed five or more servings of red meat per week also had a significantly increased risk of forearm fracture (RR = 1.23, 95% Cl 1.01-1.50) compared with women who ate red meat less than once per week. Recall of teenage diet did not reveal any increased risk of forearm fracture for women with higher consumption of animal protein or red meat during this earlier period of life. No association was observed between adult protein intake and the incidence of hip fractures, though power to assess this association was low.

Feskanich D, Willett WC, Stampfer MJ, Colditz GA
Am. J. Epidemiol. Mar 1996
PMID: 8610662 | Free Full Text