Tag Archives: review

Review: Melatonin and the Skeleton

Abstract

Melatonin and the skeleton.

Melatonin may affect bone metabolism through bone anabolic as well as antiresorptive effects. An age-related decrease in peak melatonin levels at nighttime is well documented, which may increase bone resorption and bone loss in the elderly. In vitro, melatonin reduces oxidative stress on bone cells by acting as an antioxidant. Furthermore, melatonin improves bone formation by promoting differentiation of human mesenchymal stem cell (hMSC) into the osteoblastic cell linage. Bone resorption is reduced by increased synthesis of osteoprogeterin (OPG), a decoy receptor that prevents receptor activator of NK-κB ligand (RANKL) in binding to its receptor. Moreover, melatonin is believed to reduce the synthesis of RANKL preventing further bone resorption. In ovariectomized as well as nonovariectomized rodents, melatonin has shown beneficial effects on bone as assessed by biochemical bone turnover markers, DXA, and μCT scans. Furthermore, in pinealectomized animals, bone mineral density (BMD) is significantly decreased compared to controls, supporting the importance of sufficient melatonin levels. In humans, dysfunction of the melatonin signaling pathway may be involved in idiopathic scoliosis, and the increased fracture risk in nighttime workers may be related to changes in the circadian rhythm of melatonin. In the so-far only randomized study on melatonin treatment, no effects were, however, found on bone turnover markers. In conclusion, melatonin may have beneficial effects on the skeleton, but more studies on humans are warranted in order to find out whether supplementation with melatonin at bedtime may preserve bone mass and improve bone biomechanical competence.

Amstrup AK, Sikjaer T, Mosekilde L, Rejnmark L
Osteoporos Int May 2013
PMID: 23716040

Review: Protein, Calcium, Vitamins D, C, K, and Fruits and Veggies in Osteoporosis

Abstract

The role of diet in osteoporosis prevention and management.

Diet, a modifiable osteoporosis risk factor, plays an important role in the acquisition and maintenance of bone mass. The influence of diet on bone begins in childhood; even maternal diet can influence bone mass in the offspring. A good general nutritional status and adequate dietary protein, calcium, vitamin D, fruits, and vegetables have a positive influence on bone health, while a high caloric diet and heavy alcohol consumption have been associated with lower bone mass and higher rates of fracture. The evidence for a role of other minerals and vitamins in skeletal health is not as strong, but recent evidence suggests that vitamins C and K might also have an effect on bone.

Levis S, Lagari VS
Curr Osteoporos Rep Dec 2012
PMID: 23001895

Review: Protein RDA May be Too Low

Abstract

Protein intake and bone health.

Adequate nutrition plays an important role in the development and maintenance of bone structures resistant to usual mechanical stresses. In addition to calcium in the presence of an adequate supply of vitamin D, dietary proteins represent key nutrients for bone health and thereby function in the prevention of osteoporosis. Several studies point to a positive effect of high protein intake on bone mineral density or content. This fact is associated with a significant reduction in hip fracture incidence, as recorded in a large prospective study carried out in a homogeneous cohort of postmenopausal women. Low protein intake (< 0.8 g/kg body weight/day) is often observed in patients with hip fractures and an intervention study indicates that following orthopedic management, protein supplementation attenuates post-fracture bone loss, tends to increase muscle strength, and reduces medical complications and rehabilitation hospital stay. There is no evidence that high protein intake per se would be detrimental for bone mass and strength. Nevertheless, it appears reasonable to avoid very high protein diets (i. e. more than 2.0 g/kg body weight/day) when associated with low calcium intake (i. e. less than 600 mg/day). In the elderly, taking into account the attenuated anabolic response to dietary protein with ageing, there is concern that the current dietary protein recommended allowance (RDA), as set at 0.8 g/kg body weight/day, might be too low for the primary and secondary prevention of fragility fractures.

Bonjour JP
Int J Vitam Nutr Res Mar 2011
PMID: 22139564

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

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

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

Review: Protein + Calcium – May 2003

Abstract

Calcium and protein in bone health.

Dietary protein has several opposing effects on Ca balance and its net effect on bone is not well established. It has long been recognized that increasing protein intake increases urinary Ca excretion. More recently, it has been observed that increasing dietary protein raises the circulating level of insulin-like growth factor-1, a growth factor that promotes osteoblast formation and bone growth. Other effects of protein on the Ca economy have been suggested in some studies, but they are less well established. Several studies have examined associations between protein intake and bone loss and fracture rates. In the original Framingham cohort subjects with lower total and animal protein intakes had greater rates of bone loss from the femoral neck and spine than subjects consuming more protein. In another study higher total (and animal) protein intakes were associated with a reduced incidence of hip fractures in post-menopausal women. In contrast, a high animal:plant protein intake has been associated with greater bone loss from the femoral neck and a greater risk of hip fracture in older women. Higher total and higher animal protein intakes have also been associated with increased risk of forearm fracture in younger post-menopausal women. In a recent study it was found that increasing dietary protein was associated with a favourable (positive) change in bone mineral density of the femoral neck and total body in subjects taking supplemental calcium citrate malate with vitamin D, but not in those taking placebo. The possibility that Ca intake may influence the impact of dietary protein on the skeleton warrants further investigation.

Dawson-Hughes B
Proc Nutr Soc May 2003
PMID: 14506898

Review: Protein – March 2003

Abstract

Protein and bone health: literature review and counselling implications.

For decades, public health promotion campaigns on bone health have emphasized the importance of adequate calcium and vitamin D intakes, as well as weight-bearing physical activity. However, no obvious consensus has emerged on the role of dietary protein. To identify what agreement does exist in the literature, in this article we review the theoretical basis for protein’s role in bone health, assess some recent cross-sectional and prospective studies, and generate recommendations for practice. There is general agreement in the literature that higher protein intake increases urinary calcium loss; the body compensates for this loss by increasing calcium absorption in the gut, providing that calcium intake is sufficient. A possible explanation for calcium loss, the “acid-ash” hypothesis, is discussed, and suggestions are made about food choices that may counter the calciuric effect of protein. A survey of cross-sectional and prospective studies shows equivocal results, with confounding variables complicating the analysis. Both deficient and excessive protein intakes have been shown to affect bone health negatively, although lower and upper thresholds have not been determined. Practical advice on achieving bone health is given, with an emphasis on the use of Canada’s Food Guide to Healthy Eating in setting dietary goals.

Cloutier GR, Barr SI
Can J Diet Pract Res 2003
PMID: 12631403

Review: Protein + Calcium – March 2003

Abstract

Interaction of dietary calcium and protein in bone health in humans.

Protein has both positive and negative effects on calcium balance, and the net effect of dietary protein on bone mass and fracture risk may be dependent on the dietary calcium intake. In addition to providing substrate for bone matrix, dietary protein stimulates the production of insulin-like growth factor-1 (IGF-1), a factor that promotes osteoblast-mediated bone formation. Protein also increases urinary calcium losses, by several proposed mechanisms. Increasing calcium intake may offset the negative impact of dietary protein on urinary calcium losses, allowing the favorable effect of protein on the IGF-1 axis to dominate. Several, although not all, studies are either compatible with or support this hypothesis. Protein supplements significantly reduced bone loss in elderly hip-fracture patients in a study in which both the protein and control groups received supplemental calcium. In an observational study, total protein intake was positively associated with favorable 3-y changes in femoral neck and total body bone mineral density in volunteers who received supplemental calcium citrate malate and vitamin D, but not in volunteers taking placebos. In conclusion, an adequate calcium intake may help promote a favorable effect of dietary protein on the skeleton in older individuals.

Dawson-Hughes B
J. Nutr. Mar 2003
PMID: 12612168 | Free Full Text

Review: Vitamin D + Isoflavones may be Synergistic

Abstract

Vitamin D interactions with soy isoflavones on bone after menopause: a review.

Vitamin D is known to increase Ca absorption in adults. However, the threshold vitamin D status to benefit Ca absorption is lower than the target vitamin D status for higher bone mineral density and lower fracture risk, pointing to another pathway for vitamin D to benefit bone. One possibility is by affecting osteoblast and osteoclasts directly. Vitamin D-related bone metabolism may also be affected by soy isoflavones, which selectively bind to the estrogen receptor β and may reduce bone loss in postmenopausal women. We discuss a possible synergistic effect of soy isoflavones and vitamin D on bone by affecting osteoblast and osteoclast formation and activity in postmenopausal women.

Park CY, Weaver CM
Nutrients Nov 2012
PMID: 23201836 | Free Full Text