In a recent study published in the Journal of the Academy of Nutrition and Dietetics, researchers reviewed the effects of avocado intake on cardiometabolic risk factors.
Study: Avocado Consumption and Cardiometabolic Health: A Systematic Review and Meta-Analysis. Image Credit: Nataliya Arzamasova/Shutterstock.com
Background
Excess weight and poor diet are common risk factors for non-communicable diseases. Cardiovascular disease (CVD) is among the most prevalent non-communicable diseases.
Most people consume diets not aligned with health guidelines; thus, there is a need to change behavior and decrease the risk of disease(s) among people.
Avocados are rich in unsaturated fats, and their consumption could influence the modifiable risk factors for CVD. Reports suggest that avocado consumers in Australia and the United States (US) had higher intake of mono- (MUFAs) and poly-unsaturated fatty acids (PUFAs), vitamin E, fiber, fruit, vegetables, potassium, and magnesium, and lower intake of unhealthy foods.
So far, two systematic reviews have examined the impact of avocado intake on blood lipids but have had conflicting results.
About the study
In the present study, researchers reviewed the effects of consuming diets with avocados on cardiometabolic risk factors.
They searched databases (PubMed, Scopus, ProQuest, Web of Science, and Clinical Trials Registry) for prospective observational and intervention studies with adults who were healthy, at risk of CVD, or had CVD. Comparators were diets with low/no avocados or alternative fat sources.
The primary outcome was low-density lipoprotein cholesterol (LDL-C) levels. Secondary outcomes included blood pressure, body weight, body mass index (BMI), body composition, and other lipid measures (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], apolipoprotein B, and TC-to-HDL-C ratio). Relevant data were extracted from the included studies.
Study quality was appraised using the Newcastle-Ottawa Scale for cohort studies and the Cochrane risk of bias tool for intervention studies.
The quality of evidence was rated per the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) guidelines. A meta-analysis was performed when three or more studies reported relevant data on a single outcome.
The primary meta-analysis compared the mean differences in TC, HDL-C, LDL-C, and triglycerides between avocado and control groups. Heterogeneity among studies was assessed using I2 and χ2 statistics.
Meta-regression was used to determine the effects of avocado dosage/quantity on effect size. Sub-group analyses examined the potential reasons for differences in results across studies. A sensitivity analysis was undertaken to evaluate the robustness of the synthesized result.
Findings
Of 674 records identified from database searches, 494 underwent initial screening. Full texts of 69 studies were reviewed, and 10 were selected for analysis, including one prospective cohort study and nine intervention studies (randomized controlled trials).
The trials comprised 503 participants and reported the effects of avocado consumption on diverse outcomes.
Three studies included only females; four had overweight/obese subjects, two recruited people with hypercholesterolemia, and two recruited diabetic subjects with hypertriglyceridemia.
Studies were conducted for three to 24 weeks. Avocado doses/quantities ranged from 99 g/day to 330 g/day. Besides intervention and control diets, other diets included moderate-fat, usual, high-MUFA, and energy-restricted diets.
The prospective cohort study included over 55,000 participants who were followed up for four to 11 years. Six intervention studies had some concerns of bias; the remaining three had a high risk of bias.
The cohort study scored five on the Newcastle-Ottawa scale, implying it was not high quality. All included trials reported blood lipid outcomes. Eight trials were included in the meta-analysis.
There were no significant differences in LDL-C between avocado and control groups. However, significant differences were observed between sub-groups.
For instance, LDL-C was significantly decreased in the avocado group compared to controls in studies with hypercholesterolemic subjects. Besides, TC was significantly lower in avocado consumers relative to controls, primarily in studies with hypercholesterolemic subjects or those with intervention < eight weeks.
No significant differences in triglycerides or HDL-C were observed between groups. A significant reduction in TC-to-HDL-C ratio was observed in avocado groups compared to controls.
In addition, avocado dose showed a significant inverse relationship with LDL-C and TC and a positive relationship with triglycerides and HDL-C. Furthermore, the degree of certainty in the results for lipid outcomes was rated as very low.
Conclusions
Taken together, the consumption of avocado did not impact LDL-C, triglycerides, or HDL-C levels compared to low or no consumption; nevertheless, there was a small decline in TC, and this effect was mainly driven by studies in people with hypercholesterolemia.
Although avocado consumption in hypercholesterolemic subjects also reduced LDL-C, the degree of certainty was rated as low.
This implied limited confidence in the effect estimate, and the true effect may differ when additional better-quality studies become available.