Bone mineral status and its relation with dietary estimates of net endogenous acid production in Hong Kong Chinese adolescents

A cross-sectional study to examine the association between dietary patterns and risk of overweight and obesity in Hong Kong Chinese adolescents aged 10-12 years

OBJECTIVE

To describe the dietary patterns and examine the associations of these patterns with risk of overweight and obesity in Chinese adolescents.

METHODS

Baseline data collected between November 2003 and October 2004 from 171 boys and 180 girls aged 10-12 years who participated in the Hong Kong Adolescent Bone Health Cohort Study were analyzed. Dietary intake was assessed using a food frequency questionnaire and dietary pattern calculated using factor analysis. Data on demographic characteristics, weight, height, and Tanner stage were collected. Overweight and obesity were defined using The International Obesity Task Force cutoff values. Cardiovascular fitness expressed as peak oxygen consumption was predicted using the postexercise heart rate by the 3-minute step test and was used as an objective measure of physical activity. Association between dietary patterns and risk of overweight and obesity was examined using multivariate logistic regression with adjustment for demographics, puberty, and physical activity.

RESULTS

The mean (SD) age of the study sample was 11.2 (0.6) years and there were 57 (16.2%) participants who were overweight/obese. Three dietary patterns were identified, namely, vegetables-fruits, snacks-beverages, and animal foods, fats, and condiments dominated. There was no significant linear association between each dietary pattern and the risk of overweight and obesity in this sample. Instead, the risk of overweight and obesity in this sample was positively associated with pubertal stage and inversely associated with physical activity.

CONCLUSIONS

Pubertal stage and physical activity, but not dietary patterns, were important factors contributing to the risk of overweight and obesity in this population.

Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality

Background

Modern diets have been suggested to increase systemic acid load and net acid excretion. In response, alkaline diets and products are marketed to avoid or counteract this acid, help the body regulate its pH to prevent and cure disease. The objective of this systematic review was to evaluate causal relationships between dietary acid load and osteoporosis using Hill's criteria.

Methods

Systematic review and meta-analysis. We systematically searched published literature for randomized intervention trials, prospective cohort studies, and meta-analyses of the acid-ash or acid-base diet hypothesis with bone-related outcomes, in which the diet acid load was altered, or an alkaline diet or alkaline salts were provided, to healthy human adults. Cellular mechanism studies were also systematically examined.

Results

Fifty-five of 238 studies met the inclusion criteria: 22 randomized interventions, 2 meta-analyses, and 11 prospective observational studies of bone health outcomes including: urine calcium excretion, calcium balance or retention, changes of bone mineral density, or fractures, among healthy adults in which acid and/or alkaline intakes were manipulated or observed through foods or supplements; and 19 in vitro cell studies which examined the hypothesized mechanism. Urine calcium excretion rates were consistent with osteoporosis development; however calcium balance studies did not demonstrate loss of whole body calcium with higher net acid excretion. Several weaknesses regarding the acid-ash hypothesis were uncovered: No intervention studies provided direct evidence of osteoporosis progression (fragility fractures, or bone strength as measured using biopsy). The supporting prospective cohort studies were not controlled regarding important osteoporosis risk factors including: weight loss during follow-up, family history of osteoporosis, baseline bone mineral density, and estrogen status. No study revealed a biologic mechanism functioning at physiological pH. Finally, randomized studies did not provide evidence for an adverse role of phosphate, milk, and grain foods in osteoporosis.

Conclusions

A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health.

Relationship among dietary estimates of net endogenous acid production, bone mineral density and biochemical markers of bone turnover in an Iranian general population

Chronic, low-grade metabolic acidosis due to Western diets may be a risk factor for osteoporosis. The severity can be determined in part by net endogenous acid production (NEAP). In a population-based study, a total of 1028 healthy men and women aged 20-72 years were evaluated for dietary intakes and NEAP estimates with a validated food frequency questionnaire. Dual-energy X-ray absorptiometry (DXA) was used to determine BMD of the lumbar spine (L2-L4), distal third of radius, and proximal femur. Serum CrossLaps, degradation products of the C-terminal telopeptides of type I collagen, and osteocalcin were measured by highly specific ELISA methods. Lower estimates of energy-adjusted rates of NEAP were associated with greater femoral neck BMD (p=0.01) in premenopausal women and with greater BMDs at the distal radius (p=0.001) and lumbar spine (p=0.04) in postmenopausal women. Compared with women in the highest quartile of the estimates of the energy-adjusted rates of NEAP, pre- and postmenopausal women in the lowest quartile had significantly greater means of osteocalcin [9.12 (SD+/-1.62) vs. 5.24 (SD+/-1.41) ng/ml, p=0.02 and 11.74 (SD+/-1.69) vs. 7.79 (SD+/-2.63) ng/ml, p=0.002, respectively]. Analysis by quartiles of the estimates of energy-adjusted rates of NEAP did not reveal a relationship between BMD and bone turnover markers in men. In conclusion, we found that a high energy-adjusted rate of NEAP was associated with a significantly lower BMD in women but not in men and the energy-adjusted rate of NEAP had a negative relationship with bone formation.