Low Energy Availability with and without a High-Protein Diet Suppresses Bone Formation and Increases Bone Resorption in Men: A Randomized Controlled Pilot Study (original) (raw)
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American Journal of Clinical Nutrition, 2014
Background: Although consuming dietary protein above current recommendations during energy deficit (ED) preserves lean body mass, concerns have been raised regarding the effects of high-protein diets on bone health. Objective: The objective was to determine whether calcium homeostasis and bone turnover are affected by high-protein diets during weight maintenance (WM) and ED. Design: A randomized, parallel-design, controlled trial of 32 men and 7 women were assigned diets providing protein at 0.8 [Recommended Dietary Allowance (RDA)], 1.6 (2 3 RDA), or 2.4 (3 3 RDA) g $ kg 21 $ d 21 for 31 d. Ten days of WM preceded 21 d of ED, during which total daily ED was 40%, achieved by reduced dietary energy intake (w30%) and increased physical activity (w10%). The macronutrient composition (protein g $ kg 21 $ d 21 and % fat) was held constant from WM to ED. Calcium absorption (ratio of 44 Ca to 42 Ca) and circulating indices of bone turnover were determined at day 8 (WM) and day 29 (ED). Results: Regardless of energy state, mean (6SEM) urinary pH was lower (P , 0.05) at 2 3 RDA (6.28 6 0.05) and 3 3 RDA (6.23 6 0.06) than at the RDA (6.54 6 0.06). However, protein had no effect on either urinary calcium excretion (P . 0.05) or the amount of calcium retained (P . 0.05). ED decreased serum insulin-like growth factor I, increased serum tartrate-resistant acid phosphatase, and 25hydroxyvitamin D concentrations (P , 0.01). Remaining markers of bone turnover and whole-body bone mineral density and content were not affected by either the protein level or ED (P . 0.05).
Journal of Bone and Mineral Research, 2011
Weight reduction induces bone loss by several factors, and the effect of higher protein (HP) intake during caloric restriction on bone mineral density (BMD) is not known. Previous study designs examining the longer-term effects of HP diets have not controlled for total calcium intake between groups and have not examined the relationship between bone and endocrine changes. In this randomized, controlled study, we examined how BMD (areal and volumetric), turnover markers, and hormones [insulin-like growth factor 1 (IGF-1), IGF-binding protein 3 (IGFBP-3), 25-hydroxyvitamin D, parathyroid hormone (PTH), and estradiol] respond to caloric restriction during a 1-year trial using two levels of protein intake. Forty-seven postmenopausal women (58.0 AE 4.4 years; body mass index of 32.1 AE 4.6 kg/ m 2 ) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n ¼ 26) or normal protein (NP, 18%, n ¼ 21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% AE 4.5% of body weight, and protein intake was 86 and 60 g/d in the HP and NP groups, respectively. HP compared with NP diet attenuated loss of BMD at the ultradistal radius, lumbar spine, and total hip and trabecular volumetric BMD and bone mineral content of the tibia. This is consistent with the higher final values of IGF-1 and IGFBP-3 and lower bone-resorption marker (deoxypyridinoline) in the HP group than in the NP group ( p < .05). These data show that a higher dietary protein during weight reduction increases serum IGF-1 and attenuates total and trabecular bone loss at certain sites in postmenopausal women. ß
The American journal of clinical nutrition, 2005
Exercise is beneficial for bone when adequate nutrition is provided. The role of protein consumption in bone health, however, is controversial. The objective was to ascertain the effect of high protein intake on insulin-like growth factor I (IGF-I) and markers of bone turnover during 6 mo of exercise training. Fifty-one subjects aged 18-25 y (28 men, 23 women) received a protein supplement (42 g protein, 24 g carbohydrate, 2 g fat) or a carbohydrate supplement (70 g carbohydrate) twice daily. Exercise consisted of alternating resistance training and running 5 times/wk. Plasma concentrations of IGF-I, insulin-like growth factor-binding protein 3, serum bone alkaline phosphatase, and urinary N-telopeptide collagen crosslink (NTx) concentrations were measured at 0, 3, and 6 mo after 24 h without exercise and a 12-h fast. Three-day diet records indicated no difference in energy intake between the groups. Average protein intakes after supplementation began in the protein and carbohydrate...
Pediatric Research, 2009
Peak bone mass is a major determinant of osteoporosis pathogenesis during aging. Respective influences of energy and protein supplies on skeletal growth remains unclear. We investigated the effect of a 5-mo dietary restriction on bone status in young rats randomized into six groups (n ϭ 10 per group). Control animals were fed a diet containing a normal (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 40% energyrestricted diet (ER-NP and ER-HP). High-protein intake did not modulate bone acquisition, although a metabolic acidosis was induced and calcium retention impaired. PER and ER diets were associated with a decrease in femoral bone mineral density. The compensation for protein intake in energy-restricted conditions induced a bone sparing effect. Plasma osteocalcin (OC) and urinary deoxypyridinoline (DPD) assays revealed a decreased OC/DPD ratio in restricted rats compared with C animals, which was far more reduced in PER than in ER groups. Circulating IGF-1 levels were lowered by dietary restrictions. In conclusion, both energy and protein deficiencies may contribute to impairment in peak bone mass acquisition, which may affect skeleton strength and potentially render individuals more susceptible to osteoporosis.
Calcified Tissue International, 2008
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 16month-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.
Effects of reduced energy availability on bone metabolism in women and men
Bone, 2017
The short-term effects of low energy availability (EA) on bone metabolism in physically active women and men are currently unknown. We evaluated the effects of low EA on bone turnover markers (BTMs) in a cohort of women and a cohort of men, and compared effects between sexes. These studies were performed using a randomised, counterbalanced, crossover design. Eleven eumenorrheic women and eleven men completed two 5-day protocols of controlled (CON; 45kcal·kgLBM(-1)·d(-1)) and restricted (RES; 15kcal·kgLBM(-1)·d(-1)) EAs. Participants ran daily on a treadmill at 70% of their peak aerobic capacity (VO2 peak) resulting in an exercise energy expenditure of 15kcal·kgLBM(-1)·d(-1) and consumed diets providing 60 and 30kcal·kgLBM(-1)·d(-1). Blood was analysed for BTMs [β-carboxyl-terminal cross-linked telopeptide of type I collagen (β-CTX) and amino-terminal propeptide of type 1 procollagen (P1NP)], markers of calcium metabolism [parathyroid hormone (PTH), albumin-adjusted calcium (ACa), ma...
Journal of Applied Physiology, 2008
Energy restriction coupled with high energy expenditure from arduous work is associated with an altered insulin-like growth factor-I (IGF-I) system and androgens that are coincident with losses of fat-free mass. The aim of this study was to determine the effects of two levels of dietary protein content and its effects on IGF-I, androgens, and losses of fat-free mass accompanying energy deficit. We hypothesized that higher dietary protein content would attenuate the decline of anabolic hormones and, thus, prevent losses of fat-free mass. Thirty-four men [24 (SD 0.3) yr, 180.1 (SD 1.1) cm, and 83.0 (SD 1.4) kg] participated in an 8-day military exercise characterized by high energy expenditure (16.5 MJ/day), low energy intake (6.5 MJ/day), and sleep deprivation (4 h/24 h) and were randomly divided into two dietary groups: 0.9 and 0.5 g/kg dietary protein intake. IGF-I system analytes, androgens, and body composition were assessed before and on days 4 and 8 of the intervention. Total, ...
Calcitropic Hormones and IGF-I Are Influenced by Dietary Protein
Endocrinology, 2011
Elderly men and women with protein deficiencies have low levels of circulating IGF-I, and it is likely this contributes to reduced bone formation and increased bone resorption. We hypothesized that calcitropic hormones are involved in this effect and are affected by dietary protein. We therefore investigated the influence of a low-protein diet on the PTH-1,25-dihydroxyvitamin D3 [1,25(OH) 2 D 3 ] axis and IGF-I in rats, using pamidronate to block resorption that normally contributes to mineral homeostasis. We fed 6-month-old Sprague Dawley female rats isocaloric diets containing 2.5% or 15% casein for 2 wk. Pamidronate was then administered sc (0.6 mg/kg/) for 5 d. Blood samples were collected at different time points. Serum 1,25(OH) 2 D 3 , IGF-I, PTH, calcium, and phosphorus were determined in all rats; vertebral bone strength and histomorphometric analysis were performed in rats subject to the longest low-protein diets. We found 2 wk of low protein increased PTH levels, decreased 1,25(OH) 2 D 3 , calcium, and IGF-I, suggesting that increased PTH compensates for low-protein-induced decreases in 1,25(OH) 2 D 3 . Pamidronate augmented the increased PTH after 8 wk of low protein and prevented the 1,25(OH) 2 D 3 decrease. IGF-I remained low. Protein malnutrition induced decreases in relative bone volume and trabecular thickness, which was prevented by pamidronate. Maximal load was reduced by protein restriction, but rescued by pamidronate. In summary, the low protein diet resulted in hyperparathyroidism, a reduction in circulating levels of IGF-I, and reduced 1,25(OH) 2 D 3 despite hyperparathyroidism. Blocking resorption resulted in further increases in PTH and improved microarchitecture and biomechanical properties, irrespective of vitamin D status or protein intake.
British Journal of Nutrition, 2008
In the elderly, nutritional deficiencies, such as low energy and protein intake, are suggested to increase the risk of osteoporotic fractures. Modulation of the amount and quality of protein intake under energy deficient conditions represents an interesting strategy to prevent aged-related bone loss. We investigated the effect of a 5-month dietary restriction on bone status in 16-month-old male rats. Rats were randomised into six groups (n 10 per group). Control animals were fed a normal diet containing either casein (N-C) or whey protein (N-WP). The other groups received a 40 % protein and energy-restricted diet with casein or whey protein (PER-C and PER-WP) or a normal protein and energy-restricted diet (ER-C and ER-WP). Both restrictions (PER and ER) induced a decrease in femoral bone mineral density (BMD), consistent with impaired biomechanical properties and a reduced cortical area at the diaphysis. Plasma osteocalcin and urinary deoxypyridinoline levels suggested a decrease in bone turnover in the PER and ER groups. Interestingly, circulating insulin-like growth factor 1 (IGF-1) levels were also lowered. Overall, normal protein intake did not elicit any bone sparing effect in energy-deficient rats. Regarding protein quality, neither casein nor WP appeared to significantly prevent the BMD decrease. This study confirms that nutritional deficiencies may contribute to osteopenia through decreased IGF-1 levels. Moreover, it seems that impaired bone status could not be significantly prevented by modulating the amount and quality of dietary proteins. Energy restriction: Protein deficiency: Casein or whey protein: Bone * Corresponding author: Dr Julie Mardon, fax 33 473 62 46 38, email jmardon@clermont.inra.fr