Avocado Consumption and Cardiometabolic Health: A Systematic Review and Meta-Analysis

BACKGROUND

Avocados are a rich source of unsaturated fats and bioactives, however, their role in altering cardiometabolic risk factors is unclear.

OBJECTIVE

The aim was to review the effects of consuming diets containing avocado compared with control diets containing no or low amounts of avocado on cardiometabolic risk factors in adults who were healthy, had clinical cardiovascular disease, or were at increased risk of cardiovascular disease.

METHODS

Five electronic databases were searched (PubMed, Web of Science, Scopus, ProQuest, and a Clinical Trials Registry) along with Google Scholar to identify studies published between January 1990 and November 10, 2021. Randomized controlled trials ≥3 weeks and prospective cohort studies were included. Ten studies-9 randomized controlled trials (n = 503 participants) and 1 prospective observational study (n = 55,407)-met the inclusion criteria. Outcomes assessed by means of meta-analysis were low-density lipoprotein cholesterol (LDL-C) (primary), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglycerides. Outcomes assessed by narrative review were TC to HDL-C ratio, non-HDL-C, apolipoprotein B, blood pressure, body weight, body mass index (calculated as kg/m2), waist circumference, waist-to-hip ratio, body composition, and blood glucose and insulin concentrations. Risk of bias was assessed using the Cochrane Risk of Bias tool, version 2.0 and Newcastle-Ottawa Scale; quality of evidence was examined using the Grading of Recommendations, Assessment, Development and Evaluation method. Random-effects models meta-analyses were performed when there were ≥3 studies of the same design (ie, randomized controlled trial) and reporting the same outcome. Statistical heterogeneity was assessed by calculating χ2 and I2 statistics and publication bias was assessed by funnel plots.

RESULTS

Overall, there was a small, significant reduction in TC (-5.08 mg/dL [to convert to mmol/L, divide by 38.67]; 95% CI -9.29 to -0.87 mg/dL; P = .02) in avocado vs the control groups and no significant difference in LDL-C, HDL-C, or triglycerides. Subgroup analysis demonstrated significant reductions in LDL-C (-9.4 mg/dL [to convert to mmol/L, divide by 38.67]; 95% CI -10.84 to -7.95 mg/dL; P < .00001) and TC (-7.54 mg/dL; 95% CI -9.40 to -5.68 mg/dL; P < .00001) in avocado vs control groups in hypercholesterolemic populations, and no differences were seen in normocholesterolemic populations. However, the certainty in the findings was graded as low to very low. Body weight and composition were not negatively affected by avocado consumption.

CONCLUSIONS

Avocado consumption may reduce TC and LDL-C in people with hypercholesterolemia. Avocado consumption does not negatively impact body weight. Larger, well-conducted studies are needed to have greater confidence in the role of avocado consumption on cardiovascular disease risk factors.

Soy and Gastrointestinal Health: A Review

Soybean is the most economically important legume globally, providing a major source of plant protein for millions of people; it offers a high-quality, cost-competitive and versatile base-protein ingredient for plant-based meat alternatives. The health benefits of soybean and its constituents have largely been attributed to the actions of phytoestrogens, which are present at high levels. Additionally, consumption of soy-based foods may also modulate gastrointestinal (GI) health, in particular colorectal cancer risk, via effects on the composition and metabolic activity of the GI microbiome. The aim of this narrative review was to critically evaluate the emerging evidence from clinical trials, observational studies and animal trials relating to the effects of consuming soybeans, soy-based products and the key constituents of soybeans (isoflavones, soy proteins and oligosaccharides) on measures of GI health. Our review suggests that there are consistent favourable changes in measures of GI health for some soy foods, such as fermented rather than unfermented soy milk, and for those individuals with a microbiome that can metabolise equol. However, as consumption of foods containing soy protein isolates and textured soy proteins increases, further clinical evidence is needed to understand whether these foods elicit similar or additional functional effects on GI health.

Environmental sustainability in national food-based dietary guidelines: a global review

Food-based dietary guidelines (FBDGs) provide country-specific guidance on what constitutes a healthy diet. With increasing evidence for the synergy between human and planetary health, FBDGs have started to consider the environmental sustainability of food choices. However, the number of countries that discuss environmental sustainability in their guidelines is unknown. The purpose of this Review was to identify countries with government-endorsed FBDGs that made explicit mention of environmental sustainability and to examine the breadth and depth of the inclusion of sustainability in FBDGs. The Food and Agriculture Organization of the UN identified 95 countries with FBDGs. We assessed 83 countries against our inclusion criteria, of which 37 mentioned environmental sustainability. Relevant content was assessed against a set of criteria based on the Food and Agriculture Organization's guiding principles for sustainable healthy diets. The depth to which environmental sustainability was discussed varied and it was often restricted to general explanations of what a sustainable diet is. Few FBDGs addressed why sustainability is important, how dietary changes can be made, or provided quantified advice for implementing sustainable diets.

Towards healthier and more sustainable diets in the Australian context: comparison of current diets with the Australian Dietary Guidelines and the EAT-Lancet Planetary Health Diet

BACKGROUND

There is increasing focus on moving populations towards healthier and more environmentally sustainable dietary patterns. The Australian Dietary Guidelines provide dietary patterns that promote health and wellbeing. It is unclear how these guidelines align with the more recently published global recommendations of the EAT-Lancet Planetary Health Reference Diet, and how Australian diets compare to both sets of recommendations.

METHODS

Data from one 24-h recall collected for the 2011-13 National Nutrition and Physical Activity Survey were analysed for 5,920 adults aged 19-50 years. Subgroups of this population were identified by diet quality and lower or higher consumption of foods often considered to be environmentally intensive (higher animal meat and dairy foods) or associated with healthiness (higher vegetables and lower discretionary choices). Food group and nutrient composition of Australian diets were compared to diets modelled on the Australian Dietary Guidelines and Planetary Health Reference Diet. The environmental impacts of diets were estimated using an index of combined metrics.

RESULTS

Compared with the Planetary Health Reference Diet, the Australian Dietary Guidelines contained more servings of the vegetable, dairy and alternatives, fruit, and discretionary choices. The amount of meat and alternatives was higher in the Planetary Health Reference Diet than Australian Dietary Guidelines due to the inclusion of more plant-based meat alternatives. The average Australian diet contained two to almost four times the Australian Dietary Guidelines and Planetary Health Reference Diet maximum recommended intake of discretionary choices, and provided inadequate amounts of the vegetables, cereals, unsaturated fats and meats and alternatives food groups, primarily due to lower intakes of plant-based alternatives. The average Australian diet also contained less dairy and alternatives than the Australian Dietary Guidelines. In the average Australian diet, red meat and poultry contributed 73% to the total servings of meat and alternatives compared to 33% and 10% for the Australian Dietary Guidelines and Planetary Health Reference Diet respectively. The modelled Australian Dietary Guidelines diet met the relevant nutrient reference value for all 22 nutrients examined, whereas the Planetary Health Reference Diet contained an inadequate amount of calcium. The environmental impact scores of the Planetary Health Reference Diet and Australian Dietary Guidelines were 31% and 46% lower than the average Australian diet.

CONCLUSIONS

Significant changes are required for Australians' dietary intake to align more closely with national and global dietary recommendations for health and environmental sustainability.

Eucaloric diets enriched in palm olein, cocoa butter, and soybean oil did not differentially affect liver fat concentration in healthy participants: a 16-week randomized controlled trial

BACKGROUND

Effects of dietary fat quality on liver fat remain to be elucidated. Inconsistent evidence may be influenced by fatty acid saturation, chain-length, and regio-specificity within triacylglycerol (TAG) molecules.

OBJECTIVES

We aimed to compare eucaloric diets enriched in palm olein (POo), cocoa butter (COB), and soybean oil (SBO) on liver fat concentration in healthy participants. Secondary outcomes included visceral (VAT) and abdominal subcutaneous (aSCAT) adipose tissue, plus other obesity and cardiometabolic health outcomes.

METHODS

Eighty-three healthy participants (20-45 y, BMI 18.5-27.5 kg/m2) commenced and 64 completed a 16-wk randomized parallel intervention, preceded by a 2-wk run-in. Participants consumed identical eucaloric background diets differing in test fats [contributing 20% total energy intake (%E)], providing 33%E total fat with the following ratios for PUFAs/SFAs/MUFAs: POo, 4.2/13.5/15%E; SBO, 14.4/8.8/9.4%E; COB, 2.3/19.5/11%E. Liver fat and abdominal adiposity were measured at weeks 0 and 16 using 1H-magnetic resonance spectroscopy/imaging; all other outcomes were measured at 0, 4, 8, 12, and 16 wk.

RESULTS

Fat quality did not affect liver fat concentration, VAT, aSCAT, obesity indexes, blood pressure, liver enzymes, leptin, or fasting glucose. Body fat mass decreased with SBO and COB compared with POo. SBO decreased serum total cholesterol (TC), LDL cholesterol, and TC:HDL cholesterol relative to POo [estimated marginal mean (95% CI) differences: -0.57 (-0.94, -0.20) mmol/L; -0.37 (-0.68, -0.07) mmol/L; and -0.42 (-0.73, -0.11) mmol/L, respectively]. No diet differences were observed on HDL cholesterol, TAG, apoA1, apoB, apoB:apoA1, or fecal free fatty acids (FFAs), except for lower FFA pentadecanoic acid (15:0) with COB than with SBO and POo.

CONCLUSIONS

In healthy adults, when consumed as part of eucaloric typical Australian diets, 3 different dietary fat sources did not differentially affect liver fat concentration and amounts of adipose tissue. Effects on serum lipids were inconsistent across lipid profiles. The findings must be confirmed in metabolically impaired individuals before recommendations can be made.

Strategies to Reduce Consumption of Unhealthy Foods and Beverages: Scenario Modeling to Estimate the Impact on the Australian Population's Energy and Nutrient Intakes

BACKGROUND

Overconsumption of energy-dense, nutrient-poor "discretionary" foods and beverages can indicate poor diet quality, which is a risk factor for obesity and chronic disease. With 60% of Australians exceeding the recommended intake of discretionary foods, there is a need for interventions to reduce their consumption.

OBJECTIVE

The objective was to model the impact of 26 specific scenarios to limit discretionary food intake on energy and nutrient intake.

DESIGN

The scenario modeling analysis was based on reduction strategies targeting portion size, frequency, or variety of discretionary food and beverage items consumed.

PARTICIPANTS/SETTING

Data from 12,153 respondents aged 2 to 85 years from the 2011-12 Australian National Nutrition and Physical Activity Survey were used.

OUTCOME MEASURES

The outcome measures were change in servings of discretionary foods and key nutrients (energy, total fat, saturated fat, sugar, alcohol, sodium, trans fat) for the population, and by sex, age group, weight status, and socioeconomic status.

STATISTICAL ANALYSES PERFORMED

Descriptive and inferential statistical analysis were conducted.

RESULTS

Scenarios reduced total energy intake by up to 26% across the population as a whole. The removal of discretionary foods (not beverages) resulted in the greatest reduction in servings and energy (74.8% and 25.6%, respectively), followed by the removal of discretionary items in portions greater than 143 kcal (59.1% and 24.3%) and not consuming discretionary items at main meals (51.2% and 17.8%). Targeting single categories of discretionary foods reduced energy intake by an average of 5.6% for the removal of cakes and biscuits, 4.4% for alcohol, and 3.9% for sugar-sweetened beverages. Strategies reduced total fat, saturated fat, and sugar by up to 35%, 38%, and 40% respectively.

CONCLUSIONS

Strategies that are specific to discretionary food and beverage intake targeting reductions in portion size, frequency, or variety have the potential to reduce energy intake and improve diet quality. These findings have implications for designing interventions with potential to tailor messages to current dietary habits. Exploration of how these strategies could be effectively implemented will be the focus of further research.

Modified Fasting Compared to True Fasting Improves Blood Glucose Levels and Subjective Experiences of Hunger, Food Cravings and Mental Fatigue, But Not Cognitive Function: Results of an Acute Randomised Cross-Over Trial

Recent dietary trends have prompted growing support for a variety of fasting paradigms involving extreme restriction or nil-caloric intake on fasting days. Some studies indicate that fasting may negatively influence factors including cognitive function through inducing fatigue, which may prove problematic in the context of completing a range of cognitively demanding activities required by daily obligations such as work. This randomised within-subjects cross-over trial explored the effects of true fasting (i.e., nil-caloric intake) versus modified fasting, the latter of which involved two sub-conditions: (1) extended distribution (three small meals distributed across the day; 522 kcal total); and (2) bulking (two meals eaten early in the day; 512 kcal total) over a period of 7.5 h on a single day with a 7-day washout period between conditions. Participants were n = 17 females (Body Mass Index (BMI) Mean (M) = 25.80, Standard Deviation (SD) = 2.30) aged 21-49 years. Outcomes included cognitive function, subjective mental fatigue, satiety, food cravings and blood glucose. Results showed that there were no differences in cognitive test performance between conditions;however, both modified fasting sub-conditions had improved blood glucose levels, cravings, hunger and fullness compared to true fasting. Moreover, subjective mental fatigue was significantly reduced in the modified fasting conditions relative to true fasting. Overall, results indicated that the subjective experience of true fasting and modified fasting is different, but that cognition does not appear to be impaired.

Impact of a Mobile Phone App to Increase Vegetable Consumption and Variety in Adults: Large-Scale Community Cohort Study

Background

Large-scale initiatives to improve diet quality through increased vegetable consumption have had small to moderate success. Digital technologies have features that are appealing for health-related behavior change interventions.

Objective

This study aimed to describe the implementation and evaluation of a mobile phone app called VegEze, which aims to increase vegetable intake among Australian adults.

Methods

To capture the impact of this app in a real-world setting, the Reach, Effectiveness, Adoption, Implementation, and Maintenance framework was utilized. An uncontrolled, quantitative cohort study was conducted, with evaluations after 21 and 90 days. The app was available in the Apple App Store and was accompanied by television, radio, and social media promotion. Evaluation surveys were embedded into the app using ResearchKit. The primary outcomes were vegetable intake (servings per day) and vegetable variety (types per day). Psychological variables (attitudes, intentions, self-efficacy, and action planning) and app usage were also assessed. Descriptive statistics and multiple linear regression were used to describe the impact of the app on vegetable intake and to determine the characteristics associated with the increased intake.

Results

Data were available from 5062 participants who completed the baseline survey; 1224 participants completed the 21-day survey, and 273 completed the 90-day survey. The participants resided across Australia and were mostly women (4265/5062, 84.3%) with a mean age of 48.2 years (SD 14.1). The mean increase in intake was 0.48 servings, from 3.06 servings at baseline to 3.54 servings at the end of the 21-day challenge (t₁₂₂₃=8.71; P<.001). The variety of vegetables consumed also increased by 0.35 types per day (t₁₁₂₃=9.59; P<.001). No changes in intake and variety were found from day 21 to the 90-day follow-up. Participants with the highest app usage increased their vegetable intake by 0.63 (SD 2.02) servings per day compared with 0.32 (SD 1.69) servings per day for those with the lowest app usage. On the basis of multiple linear regression, gender; age; BMI; psychological variables of self-efficacy, attitudes, intentions, and action planning specific to vegetable intake; baseline vegetable intake; and active days of app usage accounted for 23.3% of the variance associated with the change in intake (F_9,1208=42.09; P<.001). Baseline vegetable intake was the strongest predictor of change in intake (beta=−.495; P<.001), with lower baseline intake associated with a greater change in intake. Self-efficacy (beta=.116; P<.001), action planning (beta=.066; P=.02), BMI (beta=.070; P=.01), and app usage (beta=.081; P=.002) were all significant predictors of the change in intake.

Conclusions

The VegEze app was able to increase intake by half a serving in a large sample of Australian adults. Testing the app in a real-world setting and embedding the consent process allowed for greater reach and an efficient, robust evaluation. Further work to improve engagement is warranted.

Fatty acid regio-specificity of triacylglycerol molecules may affect plasma lipid responses to dietary fats-a randomised controlled cross-over trial

BACKGROUND/OBJECTIVES

Hypercholesterolaemic effects of saturated fatty acids (SFA) may be influenced not only by the chain length, but also by their specific location within the triacylglycerol (TAG) molecule. We examined the hypothesis that dietary fats rich in SFA, but containing mostly unsaturated fatty acids in the sn-2 position with most SFA in sn-1 and -3 (palm olein [PO] and cocoa butter [CB]) will have similar serum lipid outcomes to unsaturated olive oil (OO).

SUBJECTS/METHODS

Thirty-eight participants (20-40 yr, 18.5- ≤ 27.5 kg/m2) completed a 4-week randomised 3 × 3 crossover feeding intervention, preceded by 2-week run-in and separated by 2-week washout periods. Background diet contained 35 percentage of total energy (%E) fat, 18%E protein, 48%E carbohydrates, differing in test fats only (palm olein (PO), CB, OO; 20%E). Total cholesterol (TC)/high density lipoprotein cholesterol (HDL-C) ratio and related variables; TC, HDL-C, low density lipoprotein cholesterol (LDL-C), TAG, apoA1, ApoB, ApoA1 (apolipoprotein A1)/ApoB (apolipoprotein B), lipoprotein (a) (Lp(a)), NEFA, LDL sub-fractions, were assessed pre- and post-intervention. Data were analysed using mixed effects longitudinal models with a P-value < 0.05 considered significant.

RESULTS

Changes in plasma fatty acids (P < 0.05) confirmed compliance; C18:1 increased with OO compared to PO and CB; C16:0 decreased with OO and C18:0 increased following CB. No differences were seen for TC/HDL-C (mean [95%CI] change for PO, 0.08[0.00, 0.15] mmol/L; CB, 0.06 [-0.05, 0.16] mmol/L; and OO, -0.01 [-0.15, 0.13] mmol/L; P = 0.53] or any other parameter including LDL sub-fractions. OO decreased IDL-A compared to PO (-2.2 [-4.31, -0.21] mg/dL, P = 0.03).

CONCLUSION

In healthy young participants, plasma lipid responses to PO and CB, enriched in SFA but having primarily unsaturated fatty acid in the sn-2 position of TAG, did not differ from OO.

The Development of VegEze: Smartphone App to Increase Vegetable Consumption in Australian Adults

Background

Poor-quality dietary patterns are often characterized by inadequate consumption of fruits and vegetables. Changing dietary behavior is difficult, and although it is often clear what needs to change, how to enact change is more difficult. Smartphones have characteristics that may support the complexity of changing dietary behavior.

Objective

This paper describes the iterative process of developing a theory-based smartphone app called VegEze that aimed to increase vegetable consumption.

Methods

To upscale, reach target users, and create a user-friendly end product, a collaborative research-industry partnership was formed to build the app over a 20-week period. The Integrate, Design, Assess, and Share framework was used as a scientific basis to guide the development. The behavior change wheel was also used as a theoretical grounding in combination with other theory-based strategies, such as self-monitoring, social comparison, and gamification—which have all been shown to be successful in dietary change or digital health interventions. We conducted 1 consumer survey (N=1068), 1 usability testing session (N=11), and a pilot effectiveness and usability trial (N=283) to inform the design of the app.

Results

The target behavior for the app was defined as having 3 different types of vegetables at dinner. The perceived achievability of this target behavior was high; 93% of respondents (993/1068 users) felt they were likely or very likely to be able to regularly achieve the behavior. App features that users wanted included the following: recipes and meal ideas (876/1068, 82% of users), functionality to track their intake (662/1068, 62%), and information on how to prepare vegetables (545/1068, 51%). On the basis of importance of self-monitoring as a behavior change technique (BCT) and its rating by users, the vegetable tracker was a core feature of the app and was designed to be quick and simple to use. Daily feedback messages for logging intake and communicating progress were designed to be engaging and fun, using friendly, positive language and emoji icons. Daily and weekly feedback on vegetable consumption was designed to be simple, informative, and reinforce monitoring. A creative team was engaged to assist in the branding of the app to ensure it had an identity that reflected the fun and simple nature of the underlying behavior. The app included 16 BCTs, most of which were from the goals and planning subsection of the BCT taxonomy.

Conclusions

Combining a theoretical framework with an industry perspective and input resulted in an app that was developed in a timely manner while retaining its evidence-base. VegEze is an iOS app currently available in the App Store, and the overall impact of the VegEze app will be evaluated in an uncontrolled, quantitative study.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12618000481279; http://www.anzctr.org.au/TrialSearch.aspx?searchTxt=ACTRN12618000481279 (Archived by WebCite: at http://www.webcitation.org/769oG9EaA)

Randomized Trial of a High Protein, Partial Meal Replacement Program with or without Alternate Day Fasting: Similar Effects on Weight Loss, Retention Status, Nutritional, Metabolic, and Behavioral Outcomes

Higher-protein diets, meal replacements, and greater early weight loss have separately been associated with greater weight loss. We compared a high-protein, meal replacement program with daily energy restriction (DER) to one which provided greater energy restriction adding alternate day fasting (ADF + DER; alternating days of modified-fasting and DER plus 1 ad libitum day/week) on retention, weight loss, physiological, nutritional, and behavioral markers. Participants were randomized to ADF + DER or DER for 16 weeks (n = 162, age 40 ± 8 years BMI 36 ± 6 kg/m² (Mean ± SD)) plus 8 weeks weight maintenance. At week 16 weight change was -10.7 ± 0.5 kg and -11.2 ± 0.6 kg in ADF + DER and DER groups (treatment NS). Fat mass, visceral adipose tissue, and lean mass (p < 0.05) were similarly reduced between treatments. Weight loss was sustained to 24 weeks (treatment NS). Fasting LDL-cholesterol, triglycerides, insulin, hsCRP, glucose, and blood pressure all improved (p < 0.05; treatment NS). Transferrin saturation, ferritin, serum zinc, folate, and B12 improved (p < 0.05; treatment NS). Plasma thiamine and vitamin D levels decreased, reflecting lower carbohydrate intakes and seasonal changes, respectively. Food cravings, quality of life, and mood improved (treatment NS). Energy, fatigue, and pain improved slightly more in DER (p < 0.05). This study supports the use of higher protein, meal replacement programs with or without ADF in weight management.

Information needs of cancer patients and survivors regarding diet, exercise and weight management: a qualitative study

While advanced cancer is often associated with weight loss, curative cancer treatment is often associated with weight gain. Weight gain during treatment may be associated with greater risk of cancer recurrence and development of lifestyle diseases. Currently, limited resources are available to cancer patients focussed on weight control. This study assessed the information needs of patients undergoing curative chemotherapy regarding diet, exercise and weight management for the purpose of developing weight management resources. Focus groups were held with oncology practitioners, patients and survivors to determine current information provision and needs. Focus groups highlighted a perception that information provision regarding diet, exercise and weight management is insufficient and no routine assessment of weight occurs during chemotherapy. Barriers to information provision described included lack of resources and time, and practitioners' uncertainty regarding appropriate messages to provide. Patients wanted more information regarding diet, exercise and weight during treatment time. The findings of this study suggest an increase in provision of diet, exercise and weight management information is needed. This information should be evidence-based and delivered at an appropriate time by the preferred health care professional. It would also be beneficial to implement protocols regarding assessment of weight during treatment.