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Corresponding author. David Grant Medical Center, University of the Pacific, Thomas J Long School of Pharmacy and Health Sciences, 3601 Pacific Ave, Stockton, CA 95204, USA.
Department of Pharmacy, David Grant Medical Center, Travis Air Force Base, Fairfield, CA, USADepartment of Pharmacy Practice, Thomas J Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA, USA
Optimizing plasma lipoproteins is the primary goal of pharmacotherapy and diet interventions in people at risk for cardiovascular diseases. Avocados offer a rich source of monounsaturated fat and may pose beneficial effects on the lipid profile.
Objective
We aimed to perform a meta-analysis of randomized clinical trials assessing the impact of avocados on TC, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and/or triglycerides (TG).
Methods
We searched PUBMED, Cumulative Index to Nursing and Allied Health Literature, Index to Nursing and Allied Health Literature, and the Cochrane Database of Systemic Reviews from their inception to February 2015. The weighted mean difference from baseline was calculated for all endpoints. Subgroup analyses were performed to assess heterogeneity, and funnel plots inspected to assess publication bias.
Results
Ten unique studies (n = 229) were included. Avocado consumption significantly reduced TC, LDL-C, and TG by −18.80 mg/dL (95% confidence interval [CI], −24.56 to −13.05; I2, 46.9%), −16.50 mg/dL (95% CI, −22.91 to −10.10; I2, 72.5%), −27.20 mg/dL (95% CI, −44.41 to −9.99; I2, 91.1%) respectively. High-density lipoprotein cholesterol decreased nonsignificantly by −0.18 mg/dL (95% CI, −3.23 to 2.88; I2, 84.8%).
Conclusion
Avocado-substituted diets significantly decrease TC, LDL-C, and TG levels. Substituting dietary fats with avocados versus adding to the free diet should be the primary recommendation strategy. Larger trials looking at the impact of avocados on major adverse cardiovascular events are warranted.
Over 15 million Americans are currently diagnosed with coronary heart disease (CHD), the most common preventable cause of death. In 2010 alone, 545,059 deaths were attributed to CHD, with approximately one American dying every minute and 23 seconds.
2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
The preponderance of evidence suggests that having high levels of low-density lipoprotein cholesterol (LDL-C) is a positive indicator of CHD development. Reductions of LDL-C have been shown to reduce mortality and efforts to reduce LDL-C have been the main target of most lipid-lowering medications. In contrast, having elevated levels of high-density lipoprotein cholesterol (HDL-C) is considered protective against CHD development.
Cholesterol Treatment Trialists Collaboration (CTT) Efficacy of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 patients in 14 randomized trials of statins.
Fatty acids in foods typically fall within one of the four categories: saturated fats (SFAs), common in animal sources, trans fats (TFAs), common in processed foods, polyunsaturated fats (PUFAs), and monounsaturated fats (MUFAs), both common in plant-derived sources.
Although low-fat diets are generally recommended, studies have indicated that altering the types of fats you consume may further modify the risk of dyslipidemia. Favorable lipid profiles were seen when consumption of SFAs and TFAs were decreased and replaced by PUFAs and/or MUFAs.
2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials.
Moreno et al. found that a diet rich in MUFAs may have favorable effects on cardiovascular risk by preventing the oxidative modifications of LDL-C, an early event in atherosclerosis.
Currently, the Dietary Guidelines for Americans recommend a total fat intake of 20% to 35% of calories for people over the age of 18 years. The guideline promotes consuming less than 7% of calories from SFAs and replacing them with PUFAs and/or MUFAs to reduce blood cholesterol levels and lower the risk of cardiovascular disease.
The American Heart Association/American College of Cardiology Guideline on Lifestyle Management to Reduce Cardiovascular Risk recommends a reduction of SFA intake of 5% to 6% of calories.
2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
The most common type of avocado cultivated in the United States is the Hass avocado. The average Hass avocado provides 136 g of edible fruit whose oil consists of 71% MUFAs, 13% PUFAs, and 16% SFAs.
There are additional constituents of the fruit including fiber, B-vitamins and vitamins K1 and E, magnesium and potassium, and phytochemicals such as carotenoids, phenolics, and phytosterols, which may also contribute to other positive health effects.
Although the amount of calories from fat in this diet exceeds the standard recommendations, presumably because of the “healthier” nature of the MUFAs found in olive oil and nuts, mitigating the progression of dyslipidemia. Primary prevention of cardiovascular disease with a Mediterranean diet, a multicenter trial conducted in Spain that randomized patients to a Mediterranean diet consisting of either extra-virgin olive oil (1 liter weekly), mixed nuts (15 g of walnuts, 7.5 g of hazelnuts, and 7.5 g of almonds) or a control diet, showed that among subjects at high risk of cardiovascular events, extra-virgin olive oil or nuts reduced the risk of cardiovascular events by approximately 30%.
Avocados may provide a similar benefit. The purpose of this meta-analysis is to examine the use of avocados as an additive or substitute for other sources of dietary fats and the subsequent effect on TC, LDL-C, HDL-C, and TG levels.
Methods
Search strategy and selection criteria
A literature search was performed using the term “avocado” and “Persea Americana” limited to clinical trials conducted in human subjects. Three independent reviewers (S.P., B.M., S.S.) performed a literature search using PubMed (1966 to February 21, 2015), Cumulative Index to Nursing and Allied Health Literature (1982 to February 21, 2015), and Cochrane Database of Systemic Reviews (2005 to February 21, 2015). References of relevant primary articles and review articles were hand searched.
An initial screen of all abstracts was conducted followed by a thorough review of full-text publications of trials meeting the following inclusion criteria: randomized, clinical trials, human subjects, and trials evaluating avocado in the diet with reported measures of TC, LDL-C, HDL-C, and/or TG.
Studies were excluded if the intervention was less than 5 days duration or if a pill form of avocado extracts was used. In instances where data were only extractable by estimation of figures, the study was excluded.
The primary outcomes of interest were the mean change in TC, LDL-C, HDL-C, and TG from baseline.
Validity assessment
The following methodologic features to control bias were assessed: randomization, blinding, and withdrawals and/or dropouts. Jadad scores were calculated to aid in the identification of reports with overall weaker study methodologies. The maximum quality score was a total of 5 points with zero being the lowest possible score.
All data were extracted by three independent investigators (S.P., B.M., S.S.) through the use of a standardized data abstraction tool. Any discrepancy was resolved upon discussion. The following information was retrieved from each article: author identification, year of publication, study size, health status of the patient population (healthy, overweight, patients with dyslipidemia and/or diabetes), type of avocado, avocado dose, source of supplementary MUFA, avocado substituted for dietary fat vs avocado added onto baseline diet, duration of avocado diet, geographical location of the study, and study design (parallel or crossover). Pretreatment values for TC, LDL-C, HDL-C, and TG were taken from the baseline entry values in all studies.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Sample size was extracted based on actual number of subjects used in the final analysis. In trials reporting standard error (SE) and mean change in a parameter of interest, 95% confidence intervals (CIs) were calculated using the equations 95% CI = mean ± (SE × 1.96).
Conversions of TC, LDL-C, HDL-C units from mmol/L to mg/dL (United States standard) were performed by multiplying mmol/L by 38.7 and TG units from mmol/L to mg/dL by multiplying by 88.
The variables analyzed included serum lipid levels of TC, LDL-C, HDL-C, and TG. Each variable was reported as a weighted mean difference with a 95% CI using a DerSimonian and Laird random-effects model. Statistical heterogeneity was assessed using the I2 statistic. All statistical analyses were done using StatsDirect, version 2.8.0 software (StatsDirect Ltd, Cheshire, UK).
Subgroup analyses were performed to assess sources of clinical heterogeneity. Subgroups included, all studies (fixed-effects), studies with a Jadad score ≥3, health status (subjects that were healthy, overweight, having dyslipidemia and/or diabetes), avocado as the only MUFA source, avocado in addition to other dietary MUFA sources (olive oil and/or almonds), Hass type avocados, duration of intervention (< or ≥4 weeks), and avocado as an addition to a free diet. Publication bias was assessed using the Egger-weighted regression statistic and visual inspection of funnel plots.
Results
Trials included
Study identification, inclusion, and exclusion are shown in Figure 1. The initial search strategy yielded a total of 1004 citations from PubMed, 1210 citations from Cumulative Index to Nursing and Allied Health Literature, and 8 from the Cochrane Database of Systemic Reviews. Of these citations, 2176 were excluded electronically and manually by limiting our search to human subjects and clinical trials. The remaining 46 abstracts were reviewed, of which 30 were excluded for evaluating avocado for nondietary use. Sixteen full-text articles were reviewed. Of these, 6 did not include TC, LDL-C, HDL-C, or TG data. Ultimately, 10 unique studies were included in this meta-analysis, encompassing 229 study participants.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Table 2 depicts the results of subgroup analyses performed. LDL-C reduction remained significant when limited to a fixed-effects model. This was also true when analyses were limited to only studies that had Jadad scores ≥3, healthy subjects, subjects with dyslipidemia, avocados as the only MUFA source, avocado in addition to other MUFA sources, Hass avocados only, interventions <4 weeks, and interventions ≥4 weeks. However, LDL-C reduction was nonsignificant in overweight subjects, subjects who had diabetes with or without dyslipidemia and lastly avocados added to a free diet.
Table 2Results of subgroup analysis
Subgroups
N (n)
TC (95% CI)
N (n)
LDL-C (95% CI)
N (n)
HDL (95% CI)
N (n)
TG (95% CI)
All studies (random effects)
10 (229)
−18.80 (−24.56 to −13.05)
10 (229)
−16.50 (−22.91 to −10.10)
10 (229)
−0.18 (−3.23 to 2.88)
10 (229)
−27.20 (−44.41 to −9.99)
All studies (fixed effects)
10 (229)
−19.47(−21.17 to −17.78)
10 (229)
−14.27 (−15.58 to −12.96)
10 (229)
−0.40 (−1.20 to 0.40)
10 (229)
−4.53 (−7.15 to −1.90)
Jadad score ≥ 3
1 (43)
−17.70 (−30.49 to −4.91)
1 (43)
−14.40 (−24.67 to −4.13)
1 (43)
−1.80 (−6.58 to 2.98)
1 (43)
−5.40 (−23.81 to 13.01)
Healthy subjects
5 (87)
−19.11 (−20.88 to −17.34)
5 (87)
−13.49 (−14.85 to −12.13)
5 (87)
−1.79 (−2.72 to −0.85)
5 (87)
−30.82 (−55.24 to −6.39)
Overweight subjects
2 (71)
−7.67 (−29.10 to 13.76)
2 (71)
−7.87 (−23.24 to 7.49)
2 (71)
−1.04 (−4.30 to 2.21)
2 (71)
−6.54 (−24.35 to 11.27)
Dyslipidemia subjects
3 (44)
−29.37 (−41.24 to −17.50)
3 (44)
−28.50 (−42.54 to −14.47)
3 (44)
0.55 (−13.91 to 15.00)
3 (44)
−18.85 (−61.65 to 23.95)
Diabetes ± dyslipidemia subjects
2 (27)
−31.08 (−66.11 to 3.95)
2 (27)
−18.07 (−46.76 to 10.62)
2 (27)
1.29 (−3.10 to 5.68)
2 (27)
−40.45 (−75.86 to −5.04)
Avocado as MUFA source
7 (176)
−20.35 (−27.87 to −12.83)
7 (176)
−18.31 (−26.92 to −9.71)
7 (176)
−0.29 (−4.31 to 3.72)
7 (176)
−14.63 (−34.79 to 5.52)
Avocado + others as MUFA sources
3 (53)
−13.09 (−23.85 to −2.32)
3 (53)
−11.84 (−19.94 to −3.75)
3 (53)
0.02 (−3.42 to 3.26)
3 (53)
−48.97 (−60.54 to −37.40)
Hass avocados only
5 (129)
−21.37 (−31.69 to −11.05)
5 (129)
−17.19 (−26.63 to −7.75)
5 (129)
−1.56 (−5.96 to 2.83)
5 (129)
−18.05 (−39.70 to 3.60)
Studies under 4 wk
3 (76)
−23.83 (−35.50 to −12.15)
3 (76)
−19.93 (−31.26 to −8.60)
3 (76)
−1.16 (−3.04 to 0.71)
3 (76)
−19.81 (−48.21 to 8.59)
Studies 4 wk and over
7 (153)
−15.58 (−24.24 to −6.93)
7 (153)
−14.06 (−23.67 to −4.45)
7 (153)
−0.63 (−5.29 to 4.03)
7 (153)
−32.68 (−50.88 to −14.47)
Avocado added to free diet
2 (29)
7.34 (−7.31 to 22.00)
2 (29)
15.34 (−1.91 to 32.59)
2 (29)
−8.75 (−17.47 to −0.04)
2 (29)
19.02 (−32.89 to 70.92)
HDL, high-density lipoprotein; LDL-C, low-density lipoprotein; N, number of individual studies; n, total number of individual subjects; TC, total cholesterol; TG, Triglycerides.
TC was significantly reduced when limited to a fixed-effects model. Significant reductions were also seen in analyses that were limited to only studies that had Jadad scores ≥3, healthy subjects, subjects with dyslipidemia, avocados as the only MUFA source, avocado in addition to other MUFA sources, Hass avocados only, interventions <4 weeks, and interventions ≥4 weeks. However, TC reduction was nonsignificant in overweight subjects, subjects who had diabetes with or without dyslipidemia, and finally, avocados added to a free diet.
HDL-C levels decreased significantly when analysis was limited to healthy subjects and to studies that had avocados added to a free diet. It was decreased nonsignificantly in analyses that were limited to fixed effects, Jadad scores ≥3, overweight subjects, avocado as sole MUFA source, studies that involved Hass avocados only, interventions <4 weeks and interventions ≥4 weeks. Increases in HDL-C levels were nonsignificantly seen in subjects with dyslipidemia, subjects with diabetes with or without dyslipidemia and avocados in addition to other MUFA sources.
TG reduction was significantly seen in the fixed-effects analysis and in subgroup analyses that involved studies only including healthy subjects, subjects with diabetes with or without dyslipidemia, avocados with other MUFA sources and in studies with interventions ≥4 weeks. It was nonsignificantly reduced in studies with overweight subjects, subjects with dyslipidemia, avocados as the sole MUFA source, Hass avocados only, interventions less than 4 weeks and avocados added to a free diet.
Discussion
In our meta-analysis, incorporating 10 unique studies and 229 participants, using an avocado (MUFA rich) substituted diet significantly lowered TC, LDL-C, and TG levels with no impact on HDL-C. The magnitude of benefit with substituting avocados for mostly saturated dietary fats is noteworthy as red yeast rice, a commonly used supplement, which typically lowers TC by 13% and LDL-C by 19%.
Pharmaceutical agents such as Ezetimibe reduce TC, LDL-C, and TG by 13%, 18%, and 8% respectively and maximum dose Niacin lowers TC by 10%, LDL-C by 14%, and TG by 28%.
Expanded clinical evaluation of lovastatin (EXCEL) study results: III. Efficacy in modifying lipoproteins and implications for managing patients with moderate hypercholesterolemia.
In comparison, the degree of lipid profile changes with avocado substitution in the diet appears to be clinically meaningful.
There are several mechanisms with which pharmacologic agents and dietary supplements exert their lipid-profile effects. Red yeast rice and statins inhibit hydroxymethylglutaryl-coenzyme A reductase, the rate-limiting step in the synthesis of cholesterol.
Ezetimibe acts at the brush border of the small intestines and inhibits the uptake of both dietary and biliary cholesterol via the sterol transporter, Niemann-Pick C1-Like1 (NPC1L1), keeping cholesterol in the intestinal lumen for excretion.
Niacin directly inhibits TG synthesis, leading to degradation of hepatic apo-B particles and decreased secretion of very low-density lipoprotein cholesterol (VLDL-C) and LDL particles.
It is proposed that avocados reduce lipid levels by enhancing the breakdown of TG-rich lipoproteins and inhibiting VLDL-C secretion from the liver, resulting in a decrease of circulating LDL-C.
Interestingly, our results indicate that even healthy subjects with a relatively normal baseline TC (100 to 240 mg/dL), LDL-C (75 to 150 mg/dL), and TG (50 to 175 mg/dL) had significant reductions. In this group, HDL-C reduced significantly but the reduction is most likely not clinically significant. The subgroups of patients with dyslipidemia had the greatest reduction in TC and LDL-C. Conversely, overweight subjects and those with diabetes did not have significant reductions in their lipid profiles. The small sample sizes in these subgroups may not entirely explain the lack of benefit. Obese patients seem to have high VLDL concentrations leading to increased conversion of VLDL to LDL-C. Hence, reducing saturated fat intake may not be enough to compensate for the overproduction of LDL-C.
Another possibility is that insulin resistance or increased insulin concentrations lead to metabolic changes in the liver that may result in decreased LDL-C receptor responsiveness to dietary changes.
Individual variability in cardiovascular disease risk factor responses to low-fat and low-saturated-fat diets in men: body mass index, adiposity, and insulin resistance predict changes in LDL cholesterol.
Although our analysis showed beneficial effects even in healthy subjects, it is important to note that substituting avocados for saturated dietary fats as opposed to adding avocado to an already established baseline diet poses the greatest benefit. Although only two studies were available for inclusion, adding avocado to an already established baseline diet conferred no benefits to the lipid profile. As such, health policy and public health recommendations with generic statements of eating more avocados should emphasize avocado substitution over addition to free diet.
2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
Specific types of nuts are also a good source of MUFA. In a pooled analysis of 25 studies that looked at a variety of nuts (almonds, walnuts, pistachios, peanuts, and macadamias), a mean LDL-C reduction of 7.4% was evident. These results were not found for patients with obesity and/or metabolic syndrome.
These nuts were either incorporated into an existing diet or substituted one. However, most of the studies had small sample sizes and extrapolation to the general population needs further exploration.
Based on our meta-analysis, avocados have a greater LDL-C reduction in subjects with dyslipidemia but this needs further evaluation in a head-to-head trial.
There are over 60 avocado varieties available in the United States, 56 of the varieties are grown in Florida and 7 types grown in California.
Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001-2008.
Most studies included in our analyses used the Haas avocado allowing for easy extrapolation of our results to American dietary patterns. However, the authors have no reason to suspect that the benefits may not extend to the other varieties of avocados.
There are several limitations to this meta-analysis worthy of mention. The possibility of the beneficial effects on the lipid profile with avocado consumption to be driven partly by weight loss cannot be ruled out. In one of the included studies, an energy-restricted diet and avocado-substituted high MUFA diet had similar weight loss and lipid parameter changes.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Although the overall analysis effectively evaluated the use of avocados in improving lipid profiles, the subgroup analyses by health status or baseline diet are difficult to assess due to the small sample size in each subgroup. Although the primary strategy should be of dietary fat substitution from a MUFA rich source, it is possible that adding free avocados may also have health benefits independent of their lipid profile. The amount of avocado-consumed varied between studies and ranged from 0.5 to 1.5 avocados or 136 g to 300 g of avocado per day. Three of the studies actually calculated the avocado amount based on individual caloric needs. In these three studies, subjects were given the recommended 30% total fat diet, where the avocado accounted for 75% of the calories (22.5% of total caloric intake came from avocado). It is unknown as to what specific “dose” of avocado consumption is needed per day to sustain lipid-lowering effects. Most studies scored poorly using the Jadad scale; the complexity of an avocado makes it difficult to appropriately blind an intervention as such. Three of the studies evaluated the lipid profile within less than 4 weeks. Seeing the study duration related differences in our results, future lipid studies should ideally have a minimum duration of 4 weeks.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Finally, we did not evaluate other endpoints such as weight, body mass index, LDL-C particle size, or LDL-C subclass, which would have further bolstered our findings if adequate data were available.
Conclusion
Avocado-substituted diets significantly decrease TC, LDL-C, and TG levels in healthy adults with a normal body mass index. Substituting dietary fats; specifically saturated fats, with avocados versus adding to the free diet should be the public health recommendation strategy. The optimal amount of avocado and frequency of use needs further evaluation along with the nutritional similarities and differences between other different MUFA sources. Larger trials looking at the impact of avocados on major adverse cardiovascular events are warranted.
Financial disclosures
The views expressed in this material are those of the authors and do not reflect the official policy or position of the U.S. Government, the Department of Defense, the Department of the Air Force or University of the Pacific.
2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials.
Substitution of high monounsaturated fatty acid avocado for mixed dietary fats during an energy-restricted diet: effects on weight loss, serum lipids, fibrinogen, and vascular function.
Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high carbohydrate diet.
Effects of diets rich in monosaturated fatty acids on plasma lipoprotein- the Jerusalem Nutrition Study. II monounsaturated fatty acids vs carbohydrates.
Effect of a moderate fat diet with an without avocados on lipoprotein particle number, size and subclasses in overweight and obese adults: a randomized, controlled trial.
Expanded clinical evaluation of lovastatin (EXCEL) study results: III. Efficacy in modifying lipoproteins and implications for managing patients with moderate hypercholesterolemia.
Individual variability in cardiovascular disease risk factor responses to low-fat and low-saturated-fat diets in men: body mass index, adiposity, and insulin resistance predict changes in LDL cholesterol.
Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001-2008.
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