C. Murray Skeaff

Dietary Fat and Coronary Heart Disease: Summary of Evidence from Prospective Cohort and Randomised Controlled Trials

Countries Study also demonstrated strong associations between mean intakes of SFA and mean levels of serum total cholesterol [Keys, 1980]. The study prompted the ‘diet heart’ hypothesis that high intakes of SFA and cholesterol and low intakes of polyunsaturated fats (PUFA) increase the level of total cholesterol and ultimately result in the development of CHD. Indeed, the early results of the Seven Countries Study prompted an explosion of epidemiological, clinical, and basic research into the role of dietary fat in CHD. The results of dietary feeding trials (or ‘metabolic ward’ studies) which measured blood lipids in healthy volunteers after administration of controlled diets with varying intakes of fats were concordant with the findings of the associations observed between intakes of different fatty acids and changes in blood cholesterol levels observed in the ecological studies. In particular, Keys et al. [1965] and Hegsted et al. [1965] demonstrated that average change in serum cholesterol concentrations could be predicted as equations for the changes in intake of SFA and PUFA and dietary cholesterol. The concordance of the results of the ecological and the metabolic ward studies probably relate to the limited amount of measurement error in both study designs. In view of these findings, some investigators have concluded that use of cholesterol as an intermediary factor is the most rational way of studying the associations between dietary fat and CHD, Introduction

Breaking prolonged sitting reduces postprandial glycemia in healthy, normal-weight adults: a randomized crossover trial

BACKGROUND Sedentary behavior is a risk factor for cardiometabolic disease. Regularly interrupting sedentary behavior with activity breaks may lower this risk. OBJECTIVE We compared the effects of prolonged sitting, continuous physical activity combined with prolonged sitting, and regular activity breaks on postprandial metabolism. DESIGN Seventy adults participated in a randomized crossover study. The prolonged sitting intervention involved sitting for 9 h, the physical activity intervention involved walking for 30 min and then sitting, and the regular-activity-break intervention involved walking for 1 min 40 s every 30 min. Participants consumed a meal-replacement beverage at 60, 240, and 420 min. RESULTS The plasma incremental area under the curve (iAUC) for insulin differed between interventions (overall P < 0.001). Regular activity breaks lowered values by 866.7 IU · L(-1) · 9 h(-1) (95% CI: 506.0, 1227.5 IU · L(-1) · 9 h(-1); P < 0.001) when compared with prolonged sitting and by 542.0 IU · L(-1) · 9 h(-1) (95% CI: 179.9, 904.2 IU · L(-1) · 9 h(-1); P = 0.003) when compared with physical activity. Plasma glucose iAUC also differed between interventions (overall P < 0.001). Regular activity breaks lowered values by 18.9 mmol · L(-1) · 9 h(-1) (95% CI: 10.0, 28.0 mmol · L(-1) · 9 h(-1); P < 0.001) when compared with prolonged sitting and by 17.4 mmol · L(-1) · 9 h(-1) (95% CI: 8.4, 26.3 mmol · L(-1) · 9 h(-1); P < 0.001) when compared with physical activity. Plasma triglyceride iAUC differed between interventions (overall P = 0.023). Physical activity lowered values by 6.3 mmol · L(-1) · 9 h(-1) (95% CI: 1.8, 10.7 mmol · L(-1) · 9 h(-1); P = 0.006) when compared with regular activity breaks. CONCLUSION Regular activity breaks were more effective than continuous physical activity at decreasing postprandial glycemia and insulinemia in healthy, normal-weight adults. This trial was registered with the Australian New Zealand Clinical Trials registry as ACTRN12610000953033.

Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies

Objective To investigate the relation between total fat intake and body weight in adults and children. Design Systematic review and meta-analysis of randomised controlled trials and cohort studies. Data sources Medline, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials to June 2010. Inclusion criteria Randomised controlled trials and cohort studies of adults or children that compared lower versus usual total fat intake and assessed the effects on measures of body fatness (body weight, body mass index, or waist circumference) after at least six months (randomised controlled trials) or one year (in cohorts). Randomised controlled trials with any intention to reduce weight in participants or confounded by additional medical or lifestyle interventions were excluded. Data extraction Data were extracted and validity was assessed independently and in duplicate. Random effects meta-analyses, subgroups, sensitivity analyses, and metaregression were done. Results 33 randomised controlled trials (73 589 participants) and 10 cohort studies were included, all from developed countries. Meta-analysis of data from the trials suggested that diets lower in total fat were associated with lower relative body weight (by 1.6 kg, 95% confidence interval −2.0 to −1.2 kg, I2=75%, 57 735 participants). Lower weight gain in the low fat arm compared with the control arm was consistent across trials, but the size of the effect varied. Metaregression suggested that greater reduction in total fat intake and lower baseline fat intake were associated with greater relative weight loss, explaining most of the heterogeneity. The significant effect of a low fat diet on weight was not lost in sensitivity analyses (including removing trials that expended greater time and attention on low fat groups). Lower total fat intake also led to lower body mass index (−0.51 kg/m2, 95% confidence interval −0.76 to −0.26, nine trials, I2=77%) and waist circumference (by 0.3 cm, 95% confidence interval −0.58 to −0.02, 15 671 women, one trial). There was no suggestion of negative effects on other cardiovascular risk factors (lipid levels or blood pressure). GRADE assessment suggested high quality evidence for the relation between total fat intake and body weight in adults. Only one randomised controlled trial and three cohort studies were found in children and young people, but these confirmed a positive relation between total fat intake and weight gain. Conclusions There is high quality, consistent evidence that reduction of total fat intake has been achieved in large numbers of both healthy and at risk trial participants over many years. Lower total fat intake leads to small but statistically significant and clinically meaningful, sustained reductions in body weight in adults in studies with baseline fat intakes of 28-43% of energy intake and durations from six months to over eight years. Evidence supports a similar effect in children and young people.

Serum n -3 long-chain PUFA differ by sex and age in a population-based survey of New Zealand adolescents and adults

A higher proportion of n-3 long-chain PUFA in tissue lipids has been associated with a lower risk of CVD and some cancers. Diet is an important predictor of n-3 long-chain PUFA composition; however, the importance of non-dietary factors such as sex and age is unclear. We measured the proportion of n-3 long-chain PUFA in serum phospholipid, cholesterol ester and TAG of 2793 New Zealanders 15 years or older who participated in the 1997 National Nutrition Survey to determine differences by sex and age. Women had lower proportions of EPA and docosapentaenoic acid in phospholipid, by 0.07 (P = 0.004) and 0.10 (P < 0.001) mol%, respectively, and a higher proportion of DHA by 0.16 mol% (P = 0.001) compared with men. Intake of fish fat did not differ between men and women. There was a positive association between age and the proportion of EPA and DHA in phospholipid (P < 0.001). The sex differences in EPA and DHA were similar at all ages. Similar sex and age differences in serum cholesterol ester n-3 long-chain PUFA were found; only age differences were found in serum TAG. Sex and age differences in n-3 long-chain PUFA occur in the general population. Men and women may need to be considered separately when examining the association between disease risk and biomarkers of n-3 fatty acids.

The role of blood loss and diet in the aetiology of mild iron deficiency in premenopausal adult New Zealand women

OBJECTIVE To investigate the role of blood loss and diet in the aetiology of mild iron deficiency (MID) in premenopausal New Zealand women. Mild iron deficiency was defined as low, but not necessarily exhausted, iron stores (i.e. serum ferritin <20 microg/L) in the absence of anaemia (i.e. haemoglobin > or =120 g/L). DESIGN Cross-sectional study of a volunteer sample of premenopausal adult women. Information on habitual dietary intakes (using a specially designed and validated computerised iron food frequency questionnaire), health and demographic status, sources of blood loss (including menstrual blood loss estimated using a validated menstrual recall method), contraceptive use, height and weight, haemoglobin, serum ferritin and C-reactive protein were collected. SETTING Dunedin, New Zealand during 1996/1997. PARTICIPANTS Three hundred and eighty-four women aged 18-40 years. RESULTS The characteristics that were associated with an increased risk of MID were: low meat/fish/poultry intake, high menstrual blood loss, recent blood donation, nose bleeds, and low body mass index. The protective factors included shorter duration of menstrual bleeding, and multivitamin-mineral supplement use in the past year. CONCLUSIONS There are a number of potentially modifiable factors that appear to influence risk of MID. Women with low menstrual blood loss may be able to decrease their risk of MID by increasing their meat/fish/poultry intake, while those with a higher menstrual blood loss may be able to decrease their risk by decreasing their menstrual blood loss, perhaps by changing their method of contraception. Women should be encouraged to maintain a healthy body weight, and those who choose to donate blood, or who experience nose bleeds, should have their iron stores monitored.

Can dietary treatment of non-anemic iron deficiency improve iron status?

Objective: To investigate the efficacy of, first, a dietary regimen involving increased consumption of iron-rich foods and enhancers of iron absorption and decreased consumption of inhibitors of iron absorption and, second, a low dose iron chelate iron supplement, for increasing iron stores in young adult New Zealand women with mild iron deficiency (MID). Methods: The study was a 16 week randomized placebo-controlled intervention. Seventy-five women aged 18 to 40 years with MID (serum ferritin <20 μg/L and hemoglobin ≥120 g/L) were assigned to one of three groups: Placebo, Supplement (50 mg iron/day as amino acid chelate) or Diet. Participants in the Diet Group were given individual dietary counseling to increase the intake and bioavailability of dietary iron. Dietary changes were monitored by a previously validated computer-administered iron food frequency questionnaire. Results: Diet Group members significantly increased their intake of flesh foods, heme iron, vitamin C and foods cooked using cast-iron cookware and significantly decreased their phytate and calcium intakes. Serum ferritin increased in the Supplement and Diet Groups by 59% (p=0.001) and 26% (p=0.068), respectively, in comparison to the Placebo Group. The serum transferrin receptor:serum ferritin ratio decreased by 51% in the Supplement Group (p=0.0001), and there was a non-significant decrease of 22% (p=0.1232) in the Diet Group. Conclusions: This study is the first, to our knowledge, to demonstrate that an intensive dietary program has the potential to improve the iron status of women with iron deficiency.

Stability of plasma and erythrocyte fatty acid composition during cold storage

BACKGROUND The purpose of the present experiment was to determine if the fatty acid composition of plasma and erythrocyte lipids remains stable when stored at -80 degrees C. This was accomplished by repeating the fatty acid analysis of plasma and erythrocyte samples that had been analysed originally as part of two separate experiments. METHODS The original plasma and erythrocyte fatty acid analysis was completed on average within 9 and 18 months, respectively, of collecting the blood samples; the repeat analysis was done on average 2.5 and 2 years, respectively, after the initial work. All samples were stored at -80 degrees C. Identical procedures for gas-liquid chromatographic analysis of fatty acids were used for the original and repeat analysis. Plasma triglyceride and erythrocyte phosphatidylcholine fatty acids were measured. RESULTS The fatty acid compositions of plasma triglyceride and erythrocyte phosphatidylcholine were virtually unchanged between the original and repeat analysis. CONCLUSIONS In combination with the results of other studies that have found fatty acids to be stable for 1 year at -60 degrees C, the present results demonstrate that the fatty acid composition of plasma and erythrocyte lipids is stable for nearly 4 years when stored at -80 degrees C.

Men who consume vegetable oils rich in monounsaturated fat: their dietary patterns and risk of prostate cancer (New Zealand)

AbstractObjectives: To investigate (i) dietary patterns associated with consumption of vegetable oils rich in monounsaturated fatty acids (MUFA), and (ii) the risk of prostate cancer associated with consumption of these oils. Methods: A population-based case–control study was conducted in Auckland, New Zealand, involving 317 prostate cancer cases and 480 controls. A food-frequency questionnaire was used to collect data concerning consumption of MUFA-rich vegetable oils (including olive oil, canola or peanut oil) and other dietary variables. Biomarkers for fatty acids were measured in erythrocytes. Results: The group of participants who reported regular consumption of greater than 5.5 ml of MUFA-rich vegetable oils per day had a diet relatively high in monounsaturated fat, vegetables, lycopene, vitamin E, selenium, and n-3 fish oils. Increasing levels of MUFA-rich vegetable oil intake were associated with a progressive reduction in prostate cancer risk (multivariate relative risk = 0.5; 95% confidence interval 0.3–0.9; > 5.5 ml per day vs. non-consumption, p trend = 0.005), and similar trends were observed across all strata of socioeconomic status. Prostate cancer risk was not associated with intake of total MUFA or the major animal food sources of MUFA. Conclusion: This finding may be explained by the protective effect of an associated dietary pattern high in antioxidants and fish oils, an independent protective effect of MUFA-rich vegetable oils unrelated to the MUFA component, or a combination of these factors.

Very high rates of vitamin D insufficiency in women of child-bearing age living in Beijing and Hong Kong.

We aimed to describe the vitamin D status of young women living in two Chinese cities in the spring--Beijing in the north (latitude 39 degrees north) and Hong Kong (latitude 22 degrees north) in the south. We also examined the relationship between serum 25-hydroxyvitamin D and parathyroid hormone (PTH) concentrations to determine a threshold for serum 25-hydroxyvitamin D above which there is no further suppression of PTH. Finally, we examined whether dietary Ca intake influences this relationship. Non-pregnant women aged 18-40 years (n 441) were recruited between February and June. Fasting blood was collected and dietary intakes were assessed using 5 d food records. Mean serum 25-hydroxyvitamin D concentration was lower in Beijing than Hong Kong women (29 v. 34 nmol/l; P < 0.001). Vitamin D deficiency (< or = 25 nmol/l) was indicated in 40% of Beijing and 18% of Hong Kong women, and over 90% of women in both cities were insufficient (< or = 50 nmol/l). Mean Ca and vitamin D intakes were 478 mg/d and 2.0 microg/d, respectively. The relationship between 25-hydroxyvitamin D concentration and PTH was linear throughout the range with a slope of -0.36 (different from 0; P < 0.001; R 0.26), with no apparent threshold. There was no influence of Ca intake on the relationship between 25-hydroxyvitamin D and PTH concentration. Vitamin D deficiency is common and insufficiency is very common in non-pregnant women in Hong Kong and Beijing during spring. Serum 25-hydroxyvitamin D was inversely associated with PTH with no apparent threshold. Strategies such as vitamin D fortification or supplementation may be required.

The effect of increasing consumption of pulses and wholegrains in obese people: a randomized controlled trial.

Background: Wholegrain intake is inversely related to weight gain over time, but little information is available on the role of pulses in weight control. Objective: To compare weight loss, metabolic outcomes, and nutrient intakes in obese people assigned to a diet rich in pulses and wholegrains or a control diet. Methods: Randomized controlled study of 18 months with 113 volunteers (body mass index [BMI] ≥ 28 kg/m2). Diets were based on guidelines published by the National Heart Foundation of New Zealand. The intervention group was advised to consume 2 serves of pulses and 4 serves of wholegrain foods per day as substitutions for more refined carbohydrates. Results: Fiber intakes were higher, intakes of several vitamins and minerals were better maintained, and dietary glycemic index was lower in the intervention compared with the control group. Mean (standard error [SE]) weight loss at 6 months was 6.0 (0.7) kg and 6.3 (0.6) kg in the control and intervention groups, respectively, and was not different between groups (p > 0.05). Blood pressure, triglycerides, and glycemic load were lowered in both groups compared with baseline. Waist circumference was decreased at 18 months in the intervention compared with the control group (−2.8 cm; 95% confidence interval [CI]: −0.4, −5.1). Conclusions: Incorporation of pulses and wholegrain foods into a weight loss program resulted in a greater reduction in waist circumference compared with the group consuming a control diet, although no difference in weight loss was noted between groups. Retention of several nutrients was better with the pulse and wholegrain diet.