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Implications for practice and research
■ Two sessions of dietary portfolio counselling regarding cholesterol-lowering foods can result in a 13% reduction in low-density lipoprotein (LDL) cholesterol.
■ Nurses can easily incorporate advice about cholesterol-lowering foods when counselling patients who require LDL cholesterol reduction.
■ Future studies can determine if advice by nurses on dietary portfolio components can help patients achieve lower LDL cholesterol.
A heart-healthy lifestyle is the cornerstone of primary prevention of cardiovascular disease (CVD). Although conventional dietary advice has proven inferior to statin therapy for lowering serum cholesterol, studies show when certain foods are consumed in combination (dietary portfolio), serum LDL cholesterol (LDL-C) is reduced to a similar degree as first-generation statins.1 Jenkins et al conducted a 6 month clinical trial of 345 participants among four centres across Canada. The study aimed to determine whether diet counselling of foods associated with lower cholesterol achieved a greater reduction in LDL-C compared with a control diet consisting of high fiber and whole grains. Two levels of counselling intensity were evaluated, either two clinic visits of 40–60 min, or seven clinic visits of 40–60 min. Men and postmenopausal women who were free of CVD and other systemic illnesses, and were not currently taking lipid-lowering medications were enrolled.
Participants with hyperlipidaemia were stratified by centre, sex and pretreatment LDL-C levels (≥158 vs <158 mg/dl), and randomised to dietary counselling for a low-fat diet (control) or dietary portfolio of cholesterol-lowering foods with either two visits (routine) or seven visits (intensive) during a 6 month period. Dietary portfolio counselling encouraged the incorporation of plant sterols via a sterol ester-enriched margarine, viscous fiber from oats, barley, and psyllium, soy protein and nuts. At each study visit, diet histories were obtained by the dietician for the previous 7 days. Measurements included body weight, blood pressure, fasting lipid panel, apolipoproteins A-1 and B and hs-CRP. Diets were analysed using a program based on the US Department of Agriculture data (ESHA Food Processor SQL version 10.1). Adherence with the four portfolio components was estimated from the 7-day food records. Four components, if consumed as prescribed, would equal 100% adherence.
The attrition rate ranged from 18% to 26% but was similar among the three groups (p=0.33). Following the intervention, LDL-C was reduced 13.8% (95% CI 17.2% to 10.3%; p<0.001) for the intensive dietary portfolio group, 13.1% (95% CI 16.7% to 9.5%; p<.001) for the routine dietary portfolio group, and 3% (95% CI 6.1% to 0.1%; p=0.06) for the control diet group. The two dietary portfolio interventions were not significantly different (p=0.66). Apolipoprotein changes reflected LDL-C changes among groups; no differences were observed for hs-CRP. Adherence to the dietary portfolio ranged from 41% to 46%, and was associated with percentage reduction in LDL-C (r=−0.34, n=157, p<0.001).
The current study provides additional support that dietary portfolio counselling will lower LDL-C by about 13%. This LDL-C reduction was similar to that obtained in a 1 year single group study by the same investigators in which all participants were instructed to consume the dietary portfolio.2 These two studies were conducted in free living conditions similar to clinical practice. Interestingly, the frequency of dietary counselling in the current study (seven vs two sessions) did not have an effect on dietary adherence and the reduction in LDL-C, although other research shows that intervention dose influences behaviour change.3
Although this study showed modest LDL-C lowering following two sessions with dieticians, advice on cholesterol-lowering foods can be incorporated into counselling by nurses for primary prevention patients with elevated LDL-C and for higher risk patients on statin therapy who require additional LDL-C cholesterol lowering. Future research can evaluate if dietary advice offered by nurses will result in lower LDL-C. Further, it is unknown whether a modest reduction in LDL-C from a dietary portfolio intervention will result in lower CVD event rates.
Given the multisite nature of the current study, stratification by centre was appropriate, and in fact, LDL reduction percentage was different among the centres. However, the authors failed to identify the number of dieticians involved at each centre, how they were trained, what standardisation procedures were in place for counselling and how diet counselling was monitored throughout the study. Therefore, a limitation of this study is the lack of assessment of treatment fidelity.
Competing interests None.
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