Biomedical subjects

Bess Dawson-Hughes

Publications and source records attributed to Bess Dawson-Hughes.

28 records · Page 2Linked to original sources

PubMed2004

Racial/ethnic considerations in making recommendations for vitamin D for adult and elderly men and women.

Vitamin D is acquired through diet and skin exposure to ultraviolet B light. Skin production is determined by length of exposure, latitude, season, and degree of skin pigmentation. Blacks produce less vitamin D3 than do whites in response to usual levels of sun exposure and have lower 25-hydroxyvitamin D [25(OH)D] concentrations in winter and summer. Blacks in the United States also use dietary supplements less frequently than do whites. However, blacks and whites appear to have similar capacities to absorb vitamin D and to produce vitamin D after repeated high doses of ultraviolet B light. There is a growing consensus that serum 25(OH)D concentrations of at least 75-80 nmol/L are needed for optimal bone health, on the basis of studies of older white subjects living in Europe and the United States. The studies show that increasing serum 25(OH)D concentrations to this level decreases parathyroid hormone (PTH) concentrations, decreases rates of bone loss, and reduces rates of fractures. Among US blacks, low 25(OH)D concentrations are associated with higher concentrations of PTH, which are associated with lower bone mineral density. Vitamin D supplements decrease PTH and bone turnover marker concentrations among blacks. These findings suggest that improving vitamin D status would benefit blacks as well as whites. On the basis of studies conducted in the temperate zone, the intake of vitamin D3 needed to maintain a group average 25(OH)D concentration of 80 nmol/L in winter is approximately 1000 IU/d. Broad-based vitamin D supplementation is needed to remove vitamin D insufficiency as a contributing cause of osteoporosis.

Adult↗

PubMed2004

Effect of dietary protein supplements on calcium excretion in healthy older men and women.

Currently there is no consensus on the impact of dietary protein on calcium and bone metabolism. This study was conducted to examine the effect of increasing protein intake on urinary calcium excretion and to compare circulating levels of IGF-I and biochemical markers of bone turnover in healthy older men and women who consumed either a high or a low protein food supplement for 9 wk. Thirty-two subjects with usual protein intakes of less than 0.85 g/kg.d were randomly assigned to daily high (0.75 g/kg) or low (0.04 g/kg) protein supplement groups. Isocaloric diets were maintained by advising subjects to reduce their intake of carbohydrates. Selected biochemical measurements were made at baseline and on d 35 and either d 49 or 63. Changes in urinary calcium excretion in the two groups did not differ significantly over the course of the study. The high protein group had significantly higher levels of serum IGF-I (P = 0.008) and lower levels of urinary N-telopeptide (P = 0.038) over the period of d 35-49 or 63. We conclude that increasing protein intake from 0.78 to 1.55 g/kg.d with meat supplements in combination with reducing carbohydrate intake did not alter urine calcium excretion, but was associated with higher circulating levels of IGF-I, a bone growth factor, and lowered levels of urinary N-telopeptide, a marker of bone resorption. In contrast to the widely held belief that increased protein intake results in calcium wasting, meat supplements, when exchanged isocalorically for carbohydrates, may have a favorable impact on the skeleton in healthy older men and women.

Aged↗

PubMed2004

Associations between vitamin K biochemical measures and bone mineral density in men and women.

Few data exist on the association between vitamin K status and bone mineral density (BMD) in men and women of varying ages. We examined cross-sectional associations between biochemical measures of vitamin K status and BMD at the hip and spine in 741 men and 863 women (mean age, 59 yr; range, 32-86 yr) who participated in the Framingham Heart Study (1996-2000). Vitamin K status was assessed by plasma phylloquinone and percentage undercarboxylated osteocalcin (%ucOC). Among the men, low plasma phylloquinone concentrations adjusted for triglycerides and elevated serum %ucOC levels were associated with low BMD at the femoral neck (P = 0.03 and 0.009, respectively). Among postmenopausal women not using estrogen replacements, low plasma phylloquinone concentrations were associated with low spine BMD (P = 0.007), with a nonsignificant trend of an elevated serum %ucOC with low spine BMD (P = 0.08). In contrast, there were no significant associations between biochemical measures of vitamin K and BMD in either premenopausal women or postmenopausal women using estrogen replacements. Clinical trials are required to isolate any putative effects of vitamin K on rates of bone loss. The target population in these trials, particularly in regard to estrogen use, may be critical, as suggested by the findings of this study.

Adult↗

PubMed2004

Precision of bone mineral density scans at the proximal tibia in osteoarthritic subjects.

This study was conducted to assess the precision of dual-energy X-ray absorptiometry (DXA) measurements at the proximal tibia and compare it with precision at other skeletal sites. Precision at the proximal tibia was determined in two groups: 14 subjects with knee osteoarthritis (OA) and 14 normal subjects who were scanned bilaterally four times each, with repositioning. Precision of femoral neck, trochanter, and total hip was also determined in both groups. Group mean bone mineral density (BMD), standard deviation (SD), and root mean squared coefficient of variation (%CV) were determined for both tibias and hips, lumbar spine (L2-L4) and total body. The %CV of the proximal tibia ranged from 1.01% to 1.24% and did not differ significantly in the two groups. The %CV of the hips, spine, and total body ranged from 0.79% to 2.28%. We conclude that DXA scans at the proximal tibia are highly reproducible and that precision at the proximal tibia is comparable to that of the hip, spine, and total body. A larger study is needed to determine whether proximal tibia BMD measurements have research or clinical application for osteoarthritis or other conditions.

Absorptiometry, Photon↗

PubMed2003

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.

Bone Density↗

PubMed2003

Vitamin K intake and bone mineral density in women and men.

BACKGROUND: Low dietary vitamin K intake has been associated with an increased risk of hip fracture in men and women. Few data exist on the association between dietary vitamin K intake and bone mineral density (BMD). OBJECTIVE: We studied cross-sectional associations between self-reported dietary vitamin K intake and BMD of the hip and spine in men and women aged 29-86 y. DESIGN: BMD was measured at the hip and spine in 1112 men and 1479 women (macro x +/- SD age: 59 +/- 9 y) who participated in the Framingham Heart Study (1996-2000). Dietary and supplemental intakes of vitamin K were assessed with the use of a food-frequency questionnaire. Additional covariates included age, body mass index, smoking status, alcohol use, physical activity score, and menopause status and current estrogen use among the women. RESULTS: Women in the lowest quartile of vitamin K intake (macro x: 70.2 microg/d) had significantly (P < or = 0.005) lower mean (+/- SEM) BMD at the femoral neck (0.854 +/- 0.006 g/cm(2)) and spine (1.140 +/- 0.010 g/cm(2)) than did those in the highest quartile of vitamin K intake (macro x: 309 microg/d): 0.888 +/- 0.006 and 1.190 +/- 0.010 g/cm(2), respectively. These associations remained after potential confounders were controlled for and after stratification by age or supplement use. No significant association was found between dietary vitamin K intake and BMD in men. CONCLUSIONS: Low dietary vitamin K intake was associated with low BMD in women, consistent with previous reports that low dietary vitamin K intake is associated with an increased risk of hip fracture. In contrast, there was no association between dietary vitamin K intake and BMD in men.

Absorptiometry, Photon↗

PubMed2003

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.

Aged↗

PubMed2003

Precision of single vs bilateral hip bone mineral density scans.

This study was performed to determine and compare the precision of single and bilateral hip bone mineral density (BMD) measurements and to determine the precision of spinal and total body measurements by dual-energy X-ray absorptiometry (DXA). Precision (group root-mean-square average coefficient of variation) was determined in 6 subjects scanned six times each at the spine, both hips, and total body, with repositioning after each scan. Mean percentage coefficients of variance (%CVs) in BMD for single and bilateral hip scans were, respectively: 0.65% and 0.67% for the total hip, 1.16% and 1.03% for the trochanter, and 1.66% and 1.31% for the femoral neck, respectively. Mean %CV was 1.04% for spine BMD (L2-L4), 0.67% for total body BMD, 1.12% for total body bone mineral content (BMC), 0.94% for total body fat tissue, and 0.77% for total body nonfat soft tissue. We conclude that precision overall is excellent and that femoral neck precision can be improved with bilateral compared with the traditional single hip scans.

Absorptiometry, Photon↗

PubMed2002

Plasma vitamin D and 25OHD responses of young and old men to supplementation with vitamin D3.

OBJECTIVES: This study was conducted to determine whether there are age differences in the plasma parent vitamin D and 25-hydroxyvitamin D (25OHD) responses to eight weeks of supplementation with 20 microg/day of vitamin D3. METHODS: Twenty-five healthy young men (age 18-35) and 25 healthy older men (62-79) were randomly assigned to supplementation with 20 microg/day of vitamin D3 or to no intervention and followed for eight weeks. Plasma vitamin D3 was measured by high performance liquid chromatography and 25OHD was measured by competitive protein binding. RESULTS: Both young and old men in the supplemented group had pronounced, rapid and similar increases in plasma vitamin D3, whereas vitamin D3 concentrations were stable in the control group. By the end of the eight-week adaptation period, plasma vitamin D3 of young and old men had increased by 4.3 and 6.2 nmol/L respectively. In the supplemented group, mean 25OHD concentrations of both the young and old men increased during the study, and the magnitude of the change after eight weeks was nearly identical in the two age groups (22.5 and 22.1 nmol/L in the young and the old men, respectively). In the control group there was a modest decrease in 25OHD of both the young and old men. CONCLUSIONS: There appears to be no age-related impairment among men in the absorption or metabolism of 20 microg/day of vitamin D3 taken orally for at least eight weeks.

Adult↗

PubMed2002

Calcium intake influences the association of protein intake with rates of bone loss in elderly men and women.

BACKGROUND: There is currently no consensus on the effect of dietary protein intake on the skeleton, but there is some indication that low calcium intakes adversely influence the effect of dietary protein on fracture risk. OBJECTIVE: The objective of the present study was to determine whether supplemental calcium citrate malate and vitamin D influence any associations between protein intake and change in bone mineral density (BMD). DESIGN: Associations between protein intake and change in BMD were examined in 342 healthy men and women (aged > or = 65 y) who had completed a 3-y, randomized, placebo-controlled trial of calcium and vitamin D supplementation. Protein intake was assessed at the midpoint of the study with the use of a food-frequency questionnaire and BMD was assessed every 6 mo by dual-energy X-ray absorptiometry. RESULTS: The mean (+/-SD) protein intake of all subjects was 79.1 +/- 25.6 g/d and the mean total calcium intakes of the supplemented and placebo groups were 1346 +/- 358 and 871 +/- 413 mg/d, respectively. Higher protein intake was significantly associated with a favorable 3-y change in total-body BMD in the supplemented group (in a model containing terms for age, sex, weight, total energy intake, and dietary calcium intake) but not in the placebo group. The pattern of change in femoral neck BMD with increasing protein intake in the supplemented group was similar to that for the total body. CONCLUSION: Increasing protein intake may have a favorable effect on change in BMD in elderly subjects supplemented with calcium citrate malate and vitamin D.

Absorptiometry, Photon↗