Welma Stonehouse

Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient – a randomised, placebo-controlled trial

Low serum 25-hydroxyvitamin D (25(OH)D) has been shown to correlate with increased risk of type 2 diabetes. Small, observational studies suggest an action for vitamin D in improving insulin sensitivity and/or insulin secretion. The objective of the present study was to investigate the effect of improved vitamin D status on insulin resistance (IR), utilising randomised, controlled, double-blind intervention administering 100 microg (4000 IU) vitamin D(3) (n 42) or placebo (n 39) daily for 6 months to South Asian women, aged 23-68 years, living in Auckland, New Zealand. Subjects were insulin resistant - homeostasis model assessment 1 (HOMA1)>1.93 and had serum 25(OH)D concentration < 50 nmol/l. Exclusion criteria included diabetes medication and vitamin D supplementation >25 microg (1000 IU)/d. The HOMA2 computer model was used to calculate outcomes. Median (25th, 75th percentiles) serum 25(OH)D(3) increased significantly from 21 (11, 40) to 75 (55, 84) nmol/l with supplementation. Significant improvements were seen in insulin sensitivity and IR (P = 0.003 and 0.02, respectively), and fasting insulin decreased (P = 0.02) with supplementation compared with placebo. There was no change in C-peptide with supplementation. IR was most improved when endpoint serum 25(OH)D reached > or = 80 nmol/l. Secondary outcome variables (lipid profile and high sensitivity C-reactive protein) were not affected by supplementation. In conclusion, improving vitamin D status in insulin resistant women resulted in improved IR and sensitivity, but no change in insulin secretion. Optimal vitamin D concentrations for reducing IR were shown to be 80-119 nmol/l, providing further evidence for an increase in the recommended adequate levels. Registered Trial No. ACTRN12607000642482.

DHA supplementation improved both memory and reaction time in healthy young adults: a randomized controlled trial

BACKGROUND Docosahexaenoic acid (DHA) is important for brain function, and its status is dependent on dietary intakes. Therefore, individuals who consume diets low in omega-3 (n-3) polyunsaturated fatty acids may cognitively benefit from DHA supplementation. Sex and apolipoprotein E genotype (APOE) affect cognition and may modulate the response to DHA supplementation. OBJECTIVES We investigated whether a DHA supplement improves cognitive performance in healthy young adults and whether sex and APOE modulate the response. DESIGN Healthy adults (n = 176; age range: 18-45 y; nonsmoking and with a low intake of DHA) completed a 6-mo randomized, placebo-controlled, double-blind intervention in which they consumed 1.16 g DHA/d or a placebo. Cognitive performance was assessed by using a computerized cognitive test battery. For all tests, z scores were calculated and clustered into cognitive domains as follows: episodic and working memory, attention, reaction time (RT) of episodic and working memory, and attention and processing speed. ANCOVA was conducted with sex and APOE as independent variables. RESULTS RTs of episodic and working memory improved with DHA compared with placebo [mean difference (95% CI): -0.18 SD (-0.33, -0.03 SD) (P = 0.02) and -0.36 SD (-0.58, -0.14 SD) (P = 0.002), respectively]. Sex × treatment interactions occurred for episodic memory (P = 0.006) and the RT of working memory (P = 0.03). Compared with the placebo, DHA improved episodic memory in women [0.28 SD (0.08, 0.48 SD); P = 0.006] and RTs of working memory in men [-0.60 SD (-0.95, -0.25 SD); P = 0.001]. APOE did not affect cognitive function, but there were some indications of APOE × sex × treatment interactions. CONCLUSIONS DHA supplementation improved memory and the RT of memory in healthy, young adults whose habitual diets were low in DHA. The response was modulated by sex. This trial was registered at the New Zealand Clinical Trials Registry (http://www.anzctr.org.au/default.aspx) as ACTRN12610000212055.

Does consumption of LC omega-3 PUFA enhance cognitive performance in healthy school-aged children and throughout adulthood? Evidence from clinical trials.

Long-chain (LC) omega-3 PUFA derived from marine sources may play an important role in cognitive performance throughout all life stages. Docosahexaenoic acid (DHA), the dominant omega-3 in the brain, is a major component of neuronal cell membranes and affects various neurological pathways and processess. Despite its critical role in brain function, human’s capacity to synthesize DHA de novo is limited and its consumption through the diet is important. However, many individuals do not or rarely consume seafood. The aim of this review is to critically evaluate the current evidence from randomised controlled trials (RCT) in healthy school-aged children, younger and older adults to determine whether consumption of LC omega-3 PUFA improves cognitive performance and to make recommendations for future research. Current evidence suggests that consumption of LC omega-3 PUFA, particularly DHA, may enhance cognitive performance relating to learning, cognitive development, memory and speed of performing cognitive tasks. Those who habitually consume diets low in DHA, children with low literacy ability and malnourished and older adults with age-related cognitive decline and mild cognitive impairment seem to benefit most. However, study design limitations in many RCTs hamper firm conclusions. The measurement of a uniform biomarker, e.g., % DHA in red blood cells, is essential to establish baseline DHA-status, to determine targets for cognitive performance and to facilitate dosage recommendations. It is recommended that future studies be at least 16 weeks in duration, account for potential interaction effects of gender, age and apolipoprotein E genotype, include vegan/vegetarian populations, include measures of speed of cognitive performance and include brain imaging technologies as supportive information on working mechanisms of LC omega-3 PUFA.

Vegetarianism, vitamin B12 status, and insulin resistance in a group of predominantly overweight/obese South Asian women

OBJECTIVES Asian Indians are an at-risk group for vitamin B12 deficiency (because of vegetarianism) and insulin resistance (IR). Vegetarianism and consequent vitamin B12 deficiency may be associated with IR. This study aimed to describe the vitamin B12 status of predominantly overweight/obese women of South Asian origin living in Auckland and to correlate serum vitamin B12 and vegetarian status with IR as part of the larger Surya Study looking at health and lifestyle in this population. METHODS This was a cross-sectional study of 135 women at least 20 y of age who were not taking vitamin B supplements or medications that could affect vitamin B12 concentrations (serum vitamin B12 < 800 pmol/L). Data collection included serum vitamin B12, serum folate, measurements of IR (HOMA2-IR), and anthropometry. Vegetarian status was established for 124 subjects (90 non-vegetarians, 34 vegetarians). RESULTS Mean serum vitamin B12 was 227 pmol/L (95% confidence interval 210-245), serum folate was 19.1 nmol/L (18.0-20.2), and HOMA2-IR was 1.24 (1.13-1.36). Non-vegetarians had higher serum vitamin B12 levels (257 pmol/L, 235-281) than vegetarians (181 pmol/L, 159-207), P < 0.001. Vitamin B12 deficiency (<150 pmol/L) in vegetarians was 24% versus 9% in non-vegetarians. Non-vegetarians had increased body mass index (25.9 kg/m², 25.0-26.9, versus 23.9 kg/m², 22.6-25.3), waist circumference (81 ± 10.1 versus 75.8 ± 9.88 cm), and HOMA2-IR levels (1.30, 1.17-1.46, versus 1.00, 0.83-1.22). No correlation was found between serum vitamin B12 and HOMA2-IR. A significant positive correlation between non-vegetarian status and IR disappeared after controlling for body mass index. CONCLUSIONS This study population has a low serum vitamin B12 status, especially if vegetarian. The high rates of observed obesity may have overshadowed any other contributing factor to IR.

Study Protocol - Metabolic syndrome, vitamin D and bone status in South Asian women living in Auckland, New Zealand: A randomised, placebo-controlled, double-blind vitamin D intervention

BackgroundThe identification of the vitamin D receptor in the endocrine pancreas suggests a role for vitamin D in insulin secretion. There is also some limited evidence that vitamin D influences insulin resistance, and thus the early stages of the development of type 2 diabetes.MethodsEighty-four women of South Asian origin, living in Auckland, New Zealand, were randomised to receive either a supplement (4000IU 25(OH)D3 per day) or a placebo for 6 months. At baseline, all participants were vitamin D deficient (serum 25(OH)D3 <50 nmol/L), insulin resistant (HOMA-IR > 1.93) and/or hyperinsulinaemic, hyperglycemic or had clinical signs of dislipidaemia. Changes in HOMA-IR, lipids, parathyroid hormone, calcium and bone markers were monitored at 3 months and 6 months.DiscussionThis randomised, controlled trial will be the first to investigate the effect of vitamin D supplementation on insulin resistance in non-diabetic subjects. It will subsequently contribute to the growing body of evidence about the role of vitamin D in metabolic syndrome.Registered clinical.Trial registrationRegistered clinical trial – Registration No. ACTRN12607000642482

Validity and reliability of bioelectrical impedance analysis to estimate body fat percentage against air displacement plethysmography and dual-energy X-ray absorptiometry

Air displacement plethysmography (ADP) and dual-energy X-ray absorptiometry (DXA) are well-regarded methods for predicting body fat percentage (BF%). Bioelectrical impedance analysis (BIA) also predicts BF% and has distinct advantages in research settings. Aim To assess the validity of BIA against ADP and DXA to measure BF%, and to test the reliability of each method. Methods Adults (n = 166) with a wide range of body mass index (19–38 kg/m2) were tested twice during a 5-day period. ADP was conducted in a BodPod (Life Measurement Inc, Concord, CA, USA); DXA measurements on a QDR Discovery A (Hologic) and BIA measurements used the InBody 230 (Biospace Ltd., Seoul, Korea). Agreement between measurements was analysed using t-tests, effect size, linear regression models and method of triads (estimating true value). Results BIA showed excellent relative agreement to the estimated true value (ρ = 0.97 (0.96, 0.98)) and to ADP (R2 = 0.88) and DXA (R2 = 0.92), but wide limits of agreement (−4.25 to 8.37%). BIA underestimated BF% by 2%, across all values. DXA showed excellent relative agreement to the estimated true value (ρ = 0.97 (0.96, 0.98)) and with ADP (R2 = 0.92), good absolute agreement but wide limits of agreement (−6.13 to 6.91%) and under- and overestimation at high and low BF% levels, respectively. All methods showed excellent reliability with repeat measurements differing by less than 0.2% with very small 95% CIs. Conclusions BIA may be a valid method in research and population samples. All three methods showed excellent reliability.

Vitamin D supplementation suppresses age-induced bone turnover in older women who are vitamin D deficient.

There is a lack of evidence that improving vitamin D status, without changing calcium intake, has a positive effect on bone turnover as indicated by bone marker changes. The objective was to measure the effect of vitamin D supplementation, in vitamin D deficient women (25(OH)D concentration<50 nmol/L), on osteocalcin (OC) and C-telopeptide (CTX). The study design was a randomised controlled intervention administering 4000 IU vitamin D3 or placebo daily for 6 months to South Asian women, aged>20 years. Subjects were stratified by age and menopausal status. Median (25th, 75th percentile) serum 25(OH)D increased significantly from 21 (11, 40) to 75 (55, 84) nmol/L with supplementation. In women>49 years or postmenopausal (n=26), who were not supplemented (n=13), CTX and OC levels increased (P=0.001, P=0.004 respectively), indicating an increased rate of bone turnover. With supplementation CTX decreased (P=0.012) and there was no significant change in OC. In women who were under 49 years and premenopausal (n=55; 29 supplemented), there was no significant response to supplementation in either CTX or OC. We conclude that correcting vitamin D deficiency in older women suppresses the age-induced increase in bone turnover and reduces bone resorption which would normally be exacerbated in conditions of low serum 25(OH)D.

Vitamin D status and attitudes towards sun exposure in South Asian women living in Auckland, New Zealand.

OBJECTIVE To determine the vitamin D status of women of South Asian origin living in Auckland, New Zealand, and to investigate their attitudes and behaviours with regard to sun exposure. DESIGN Cross-sectional study. SETTING Auckland, New Zealand. SUBJECTS Women of South Asian origin (n 235) aged 20 years and older were tested for serum 25(OH)D, and 228 were included in these analyses. Of these, 140 completed a questionnaire about attitudes and behaviours to sun exposure, and health motivation. Exclusion criteria included high dose (>1000 IU/d) supplementation with 25(OH)D3, or any supplementation with 1,25(OH)2D3. RESULTS As serum vitamin D concentrations were not normally distributed, data are reported as median (25th, 75th percentile). Median serum 25(OH)D3 was 27.5 (18.0, 41.0) nmol/l. Adequate concentrations (>50 nmol/l) were observed in only 16 % of the subjects. Concern about skin cancer and the strength of the New Zealand sun were the most prevalent reasons given for sun avoidance, with 65 % saying they did avoid the sun. However, a seasonal variation was observed, with concentrations reducing significantly (P < 0.001) from summer through to early spring by 19.5 nmol/l. CONCLUSIONS The results of the present study suggest that South Asian women are at high risk of hypovitaminosis D, due, in part, to deliberate sun avoidance and an indoor lifestyle, and that they are especially vulnerable in winter and spring.

Kiwifruit consumption favourably affects plasma lipids in a randomised controlled trial in hypercholesterolaemic men

The unique composition of green kiwifruit has the potential to benefit CVD risk. The aim of the present study was to investigate the effect of consuming two green kiwifruits daily in conjunction with a healthy diet on plasma lipids and other metabolic markers and to examine response according to APOE genotype in hypercholesterolaemic men. After undergoing a 4-week healthy diet, eighty-five hypercholesterolaemic men (LDL-cholesterol (LDL-C) > 3.0 mmol/l and TAG < 3 mmol/l) completed an 8-week randomised controlled cross-over study of two 4-week intervention sequences of two green kiwifruits per d plus healthy diet (intervention) or healthy diet alone (control). Anthropometric measures, blood pressure (BP) and fasting blood samples (plasma lipids, serum apoA1 and apoB, insulin, glucose, high-sensitivity C-reactive protein (hs-CRP)) were taken at baseline, and at 4 and 8 weeks. After the kiwifruit intervention, plasma HDL-cholesterol (HDL-C) concentrations were significantly higher (mean difference 0.04; 95% CI 0.01, 0.07 mmol/l; P = 0.004) and the total cholesterol (TC):HDL-C ratio was significantly lower (mean difference 20.5; 95% CI 20.24, 20.05 mmol/l; P = 0.002) compared with the control. In carriers of the APOE4 allele, TAG decreased significantly (mean difference -0.18; 95% CI -0.34, -0.02 mol/l; P = 0.03) with kiwifruit compared with control. There were no significant differences between the two interventions for plasma TC, LDL-C, insulin, glucose, hs-CRP and BP. The small but significant increase in HDL-C and decrease in TC:HDL-C ratio and TAG (in APOE4 carriers) suggest that the regular inclusion of green kiwifruit as part of a healthy diet may be beneficial in improving the lipid profiles of men with high cholesterol.

The effect of gold kiwifruit consumed with an iron fortified breakfast cereal meal on iron status in women with low iron stores: A 16 week randomised controlled intervention study

BackgroundDietary treatment is often recommended as the first line of treatment for women with mild iron deficiency. Although it is well established that ascorbic acid enhances iron absorption, it is less clear whether the consumption of ascorbic acid rich foods (such as kiwifruit) with meals fortified with iron improves iron status. The aim of this study is to investigate whether the consumption of ZESPRI® GOLD kiwifruit (a fruit high in ascorbic acid and carotenoids) with an iron fortified breakfast cereal meal increases iron status in women with low iron stores.Methods/DesignEighty nine healthy women aged 18-44 years with low iron stores (serum ferritin (SF) ≤ 25 μg/L, haemoglobin (Hb) ≥ 115 g/L) living in Auckland, New Zealand were randomised to receive an iron fortified breakfast cereal (16 mg iron per serve) and either two ZESPRI® GOLD kiwifruit or a banana (low ascorbic acid and carotenoid content) to eat at breakfast time every day for 16 weeks. Iron status (SF, Hb, C-reactive protein (CRP) and soluble transferrin receptor (sTfR)), ascorbic acid and carotenoid status were measured at baseline and after 16 weeks. Anthropometric measures, dietary intake, physical activity and blood loss were measured before and after the 16 week intervention.DiscussionThis randomised controlled intervention study will be the first study to investigate the effect of a dietary based intervention of an iron fortified breakfast cereal meal combined with an ascorbic acid and carotenoid rich fruit on improving iron status in women with low iron stores.Trial registrationACTRN12608000360314