Alexandra Chisholm

A diet rich in walnuts favourably influences plasma fatty acid profile in moderately hyperlipidaemic subjects

Objective: To compare two low fat diets one rich in walnuts on parameters of lipid metabolism in a group of hyperlipidaemic subjects.Design: A randomised cross over study.Setting: Department of Human Nutrition, University of Otago, Dunedin, New ZealandSubjects: Twenty one men with mean (s.d) levels of total and LDL cholesterol of 6.58 (0.60) and 4.63 (0.58) respectively.Interventions: For two periods of four weeks subjects were asked to consume two low fat diets (fat 30% total energy), one containing, on average, 78 g/d walnuts. Walnuts obtained through Lincoln University and the Walnut Growers Group (South Canterbury).Results: Participants reported a higher total fat intake on the walnut diet (38% compared with 30% on the low fat diet P<0.01) The most consistent change in fatty acid profile of triacylglycerol, phospholipid and cholesterol ester on the walnut diet was a significant (P<0.01) increase in linoleic acid. Triacylglycerol linolenate also increased significantly (P<0.01). Total and LDL cholesterol were lower on both experimental diets than at baseline, 0.25 mmol/l and 0.36 mmol/l respectively on the walnut diet and 0.13 mmol/l and 0.20 mmol/l respectively on the low fat diet. High density lipoprotein cholesterol was higher on both the walnut and low fat diets when compared to baseline (0.15 mmol/l and 0.12 mmol/l, respectively). When comparing the walnut and low fat diets only apo B was significantly lower (P<0.05) on the walnut diet.Conclusions: Despite an unintended increase in the total fat intake on the walnut diet, fatty acid profile of the major lipid fractions showed changes which might be expected to reduce risk of cardiovascular disease. The reduction of apolipoprotein B suggests a reduction in lipoprotein mediated risk, the relatively low myristic acid content of both diets perhaps explaining the absence of more extensive differences in lipoprotein levels on the two diets.Sponsorship: Nutrition Department University of Otago, New Zealand.

Plant sterol-enriched spread enhances the cholesterol-lowering potential of a fat-reduced diet

Objective: To determine the effect of a plant sterol-enriched spread on plasma cholesterol concentrations when replacing butter or a standard polyunsaturated spread in a diet containing 30% of energy fat.Design: Parallel butter phase followed by double-blind, randomized, cross-over polyunsaturated spread phases.Setting: General community.Subjects: Volunteer sample of 50 free-living men and women with mean age (s.d.) 46.7 y (10.5), moderately elevated plasma total cholesterol 5.95 mmol/l (0.78), and body mass index 26.0 (3.9) kg/m2.Intervention: Participants ate a moderately low-fat diet (30% of energy) for the 11-week intervention. During the first 3 weeks the diet included 20 g per day of butter. Participants were then randomized to replace the butter with 25 g of polyunsaturated spread with or without 2 g of plant sterols for 4 weeks, crossing over in the last 4 weeks to the alternate spread.Main outcome measures: Plasma cholesterol and fatty acids.Results: Replacing butter with a standard polyunsaturated fat spread reduced mean plasma total cholesterol concentrations by 4.6% (from 6.09 (0.82) to 5.81 (0.77) mmol/l, P<0.01) and low-density lipoprotein cholesterol by 5.5% (from 3.98 (0.76) to 3.76 (0.74) mmol/l, P<0.05). Replacing butter with a polyunsaturated spread containing plant sterols reduced plasma total cholesterol by 8.9% (from 6.09 (0.82) to 5.55 (0.76) mmol/l, P<0.01) and low density lipoprotein cholesterol by 12.3% (from 3.98 (0.76) to 3.49 (0.72) mmol/l, P<0.01). Plasma high density lipoprotein cholesterol concentration was the same on the three diets.Conclusion: In people with moderately raised plasma cholesterol concentrations consuming reduced-fat diets the reduction in plasma total and low-density lipoprotein cholesterol concentrations achieved by replacing butter with a polyunsaturated spread is enhanced by addition of plant sterols.Sponsorship: Partially funded by a grant to the University of Otago from Unilever Research.

Assessment of three levels of folic acid on serum folate and plasma homocysteine: a randomised placebo-controlled double-blind dietary intervention trial.

Objective: To determine the minimum effective dose of folic acid required to appreciably increase serum folate and to produce a significant reduction in plasma total homocysteine (tHcy).Design: Double-blind, randomised placebo-controlled intervention trial.Setting: Community-based project in a New Zealand city.Subjects: Seventy free living men and women with tHcy≥10 µmol/l. Mean age (range) was 58 (29–90) y.Interventions: Daily consumption over 4 weeks of 20 g breakfast cereal either unfortified (placebo) or fortified with 100, 200 or 300 µg folic acid. Dietary intake was determined by weighed diet records and consumption of commercially fortified products was avoided.Main outcome measures: Plasma tHcy and serum folate concentrations.Results: Average serum folate concentrations (95% CI) increased significantly in the treatment groups relative to the control group by 28(9–51)%, 60(37–87)% and 79(51–114)% for supplementation with 100, 200 and 300 µg folic acid, respectively. A reduction in tHcy was observed, being 16(8–22)%, 12(4–18)% and 17(9–24)% in the three treatment groups, respectively.Conclusions: A regular intake of as little as 100 µg folic acid per day was sufficient to lower tHcy in persons at the upper end of the normal range for tHcy. Low-level fortification may also be appropriate for lowering the risk of neural tube defects given that, when aggregated from all sources, the total intake of folic acid may be sufficiently high to adequately improve the folate status of young women.Funding: The breakfast cereals were supplied and the study partially funded by Kellogg Company.

Determining optimal approaches for weight maintenance: a randomized controlled trial

Background: Weight regain often occurs after weight loss in overweight individuals. We aimed to compare the effectiveness of 2 support programs and 2 diets of different macronutrient compositions intended to facilitate long-term weight maintenance. Methods: Using a 2 × 2 factorial design, we randomly assigned 200 women who had lost 5% or more of their initial body weight to an intensive support program (implemented by nutrition and activity specialists) or to an inexpensive nurse-led program (involving “weigh-ins” and encouragement) that included advice about high-carbohydrate diets or relatively high-monounsaturated-fat diets. Results: In total, 174 (87%) participants were followed-up for 2 years. The average weight loss (about 2 kg) did not differ between those in the support programs (0.1 kg, 95% confidence interval [CI] −1.8 to 1.9, p = 0.95) or diets (0.7 kg, 95% CI −1.1 to 2.4, p = 0.46). Total and low-density lipoprotein (LDL) cholesterol levels were significantly higher among those on the high-monounsaturated-fat diet (total cholesterol: 0.17 mmol/L, 95% CI 0.01 to 0.33; p = 0.040; LDL cholesterol: 0.16 mmol/L, 95% CI 0.01 to 0.31; p = 0.039) than among those on the high-carbohydrate diet. Those on the high-monounsaturated-fat diet also had significantly higher intakes of total fat (5% total energy, 95% CI 3% to 6%, p < 0.001) and saturated fat (2% total energy, 95% CI 1% to 2%, p < 0.001). All of the other clinical and laboratory measures were similar among those in the support programs and diets. Interpretation: A relatively inexpensive program involving nurse support is as effective as a more resource-intensive program for weight maintenance over a 2-year period. Diets of different macronutrient composition produced comparable beneficial effects in terms of weight loss maintenance. ClinicalTrials.gov trial register no. NCT00128336.

Coconut oil consumption and cardiovascular risk factors in humans

Coconut oil is being heavily promoted as a healthy oil, with benefits that include support of heart health. To assess the merits of this claim, the literature on the effect of coconut consumption on cardiovascular risk factors and outcomes in humans was reviewed. Twenty-one research papers were identified for inclusion in the review: 8 clinical trials and 13 observational studies. The majority examined the effect of coconut oil or coconut products on serum lipid profiles. Coconut oil generally raised total and low-density lipoprotein cholesterol to a greater extent than cis unsaturated plant oils, but to a lesser extent than butter. The effect of coconut consumption on the ratio of total cholesterol to high-density lipoprotein cholesterol was often not examined. Observational evidence suggests that consumption of coconut flesh or squeezed coconut in the context of traditional dietary patterns does not lead to adverse cardiovascular outcomes. However, due to large differences in dietary and lifestyle patterns, these findings cannot be applied to a typical Western diet. Overall, the weight of the evidence from intervention studies to date suggests that replacing coconut oil with cis unsaturated fats would alter blood lipid profiles in a manner consistent with a reduction in risk factors for cardiovascular disease.

Nuts Improve Diet Quality Compared to Other Energy-Dense Snacks While Maintaining Body Weight

Previous studies have reported that regular nut consumption reduces cardiovascular disease (CVD) risk and does not promote weight gain despite the fact that nuts are energy-dense. However, no studies have investigated the body composition of those regularly consuming nuts compared to similar intakes of other snacks of equal energy density. This parallel study (n = 118) examined the effects of providing daily portions (~1100 kJ/d) of hazelnuts, chocolate, or potato crisps compared to a control group receiving no snacks for twelve weeks. Effects on body weight and composition, blood lipids and lipoproteins, resting metabolic rate (RMR), appetite indices, and dietary quality were compared. At week 12, there was no significant difference in any of the outcome measurements between the groups except for dietary quality, which improved significantly in the nut group. Nuts can be incorporated into the diet without adversely affecting body weight and can improve diet quality.

Long-term consumption of high energy-dense snack foods on sensory-specific satiety and intake

BACKGROUND The sensory attributes of foods may have an important influence on intake because of sensory-specific satiety (SSS). Foods with high SSS may aid in body weight maintenance as a result of termination of consumption before metabolic satiety. No studies have investigated whether long-term exposure to a food might change SSS or how this affects food intake. OBJECTIVE The objective was to compare the effects of daily consumption of 3 energy-dense snack foods (hazelnuts, chocolate, and potato chips) for 12 wk on SSS and ad libitum intake during a tasting session. DESIGN One hundred eighteen participants took part in this randomized, controlled, parallel study with 4 arms: control group (no additional food) or ∼1100 kJ/d for each snack. SSS, food intake, and body composition were measured at baseline and at week 12. RESULTS Daily consumption of snacks for 12 wk resulted in a statistically significant reduction in SSS in all 3 snack groups (P = 0.015). However, no such changes were seen in the control group (P = 0.608). Ad libitum energy intake increased over the study during the tasting sessions for the snack food across all groups, including the control group (P = 0.039). Inverse associations were found between baseline SSS and BMI (P = 0.039), percentage body fat (P = 0.013), and fat mass (P = 0.004). CONCLUSION Habitual consumption of a high energy-dense snack food results in a decrease in SSS, which could lead to a higher energy intake of the snack. This trial was registered at www.anzctr.org.au as ACTRN12609000265279.

Effects of different forms of hazelnuts on blood lipids and α-tocopherol concentrations in mildly hypercholesterolemic individuals.

Background/Objectives:Diets high in nuts reduce cholesterol, probably due to their favorable lipid profile and other bioactive substances. However, the physical form of the nut may be important as the cell wall of intact nuts may limit the hypocholesterolemic effect of nuts by reducing lipid bioavailability. Therefore, we investigated the effects on blood lipids of incorporating three different forms of hazelnuts (ground, sliced and whole) into the usual diet.Subjects/Methods:In a randomized crossover study with three phases, 48 mildly hypercholesterolemic participants were asked to consume 30 g of ground, sliced or whole hazelnuts for 4 weeks. Body weight, plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triacylglycerol (TAG), apolipoprotein (apo) A1, apo B100 and α-tocopherol were measured at baseline and at the end of each dietary phase.Results:There were no significant differences in any outcome variable between the different forms of nuts (all P⩾0.159). However, compared with baseline, mean values at the end of each hazelnut intervention were significantly higher for HDL-C (P=0.023) and α-tocopherol (P=0.005), and significantly lower for TC (P<0.001), LDL-C (P<0.001), TC:HDL-C ratio (P<0.001), apo B100 (P=0.002) and apo B100:apo A1 ratio (P<0.001), with no significant difference in body weight (P=0.813).Conclusions: The ingestion of three different forms of hazelnuts equally improved the lipoprotein profile and α-tocopherol concentrations in mildly hypercholesterolemic individuals. Hazelnuts can therefore be incorporated into the usual diet as a means of reducing cardiovascular disease risk.

Variants in the cholesterol ester transfer protein and lipoprotein lipase genes are predictors of plasma cholesterol response to dietary change

There are no definitive explanations as to why individuals with hypercholesterolemia, a major cardiovascular risk factor, respond differently to dietary change. Fifty five free-living individuals completed a double crossover trial with two dietary regimens, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat), each phase continuing for 4 weeks. Extensive genotyping and several measures of dietary compliance have provided further insights regarding the determinants of extent of cholesterol response to changes in the nature of dietary fat. Individuals with the CETP B1B1 genotype and the LPL X447+ allele showed an average 0. 44 (95% CI: 0.22, 0.66) and 0.45 (95% CI: 0.18, 0.72) mmol/l greater change in total cholesterol, respectively, than those with one or more CETP B2 allele or homozygous for the LPL S447 allele when comparing diets high and low in saturated fat. Indices of dietary compliance including changes in reported saturated and polyunsaturated fat intake and change in triglyceride linoleate were not significantly different between the CETP genotypes. Change in reported saturated (r=0.36, P=0.04) and polyunsaturated (r=0.22, P=0. 05) fat intake and change in triglyceride linoleate (reflecting polyunsaturated fat intake) (r=0.21, P=0.07), also predicted total cholesterol response to dietary fat changes. In multivariate analyses, variation in the cholesterol ester transfer protein and lipoprotein lipase genes predicted response independent of measures of dietary compliance, suggesting that these two genes are important determinants of variation in cholesterol response to dietary change in free-living individuals.

Genetic factors associated with response of LDL subfractions to change in the nature of dietary fat

A preponderance of dense low density lipoprotein (LDL) particles is associated with an increased risk of coronary heart disease. It has been shown that dense LDL levels can be modified by diet. We investigated the contribution of polymorphisms in the genes for apolipoprotein (apo) B, apo AIV, lipoprotein lipase (LPL) and cholesterol ester transfer protein (CETP) to variation in the changes in plasma concentrations of dense LDL between a high saturated and a high polyunsaturated fatty acid diet. A total of 46 freeliving individuals (19 men and 27 women) completed a crossover trial with two dietary interventions of 4 weeks each, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat). Overall, the change in dense LDL between the saturated and polyunsaturated fat period was 0.17+/-0.33 mmol/L and this change was similar in men and women. Of the polymorphisms studied only variation in the apo AIV gene causing the substitution of histidine for glutamine at position 360 (Q360H) was associated with significant differences in the change in dense LDL concentration. Apo AIV Q/H individuals (n=6) showed a three-fold greater change in dense LDL cholesterol unadjusted for Lp(a) levels than Q/Q individuals (0.46+/-0.27 versus 0.12+/-0.31 mmol/L, p=0.02). The greater decrease in dense LDL cholesterol with an increase in polyunsaturated fat seen in those with the apo AIV H360 variant, who represent roughly 10% of the general population, suggests that they may benefit most from a PUFA rich lipid lowering diet.