NEW META-ANALYSIS SUPPORTS ALMONDS’ ROLE IN HEART HEALTH
(21st September 2016) A new systematic review and meta-analysis published in the Journal of Nutritional Science found that eating almonds results in significant reductions in total cholesterol, “bad” LDL-cholesterol and triglycerides, while having no significant impact on “good” HDL cholesterol levels , adding to the weight of evidence that supports the consumption of almonds as part of a healthy diet to help maintain healthy blood lipid levels and reduce the risk of heart disease.
Additional findings from sub-group analyses showed that blood lipid levels were most substantially improved in the studies in which the dose of almonds was at least 45 g/day and in which the studied populations had elevated blood lipid levels at baseline. The study, conducted by Dr. Kathy Musa-Veloso and colleagues, was funded by the Almond Board of California and independently evaluated in a peer-reviewed journal.
The analysis included 18 published randomized controlled trials and a total of 837 participants. When data from all of the studies were pooled, the reduction in total cholesterol was 0.153 mmol/L (5.92 mg/dL). When the meta-analysis was restricted to those studies where the amount of almonds consumed was at least 45 g/day (~1.5 oz/day), the reduction in total cholesterol was 0.212 mmol/L (8.20 mg/dL). These data suggest that the effects of almonds on total cholesterol are dose-dependent, with a larger almond intake resulting in a greater reduction in total cholesterol. When the meta-analysis was based on studies in which the subjects had elevated total cholesterol levels (at baseline), the reduction in total cholesterol was 0.271 mmol/L (10.48 mg/dL), suggesting that the effects of almonds on total cholesterol levels are most impactful in these individuals.
A similar pattern was observed for LDL-cholesterol. Specifically, when data from all of the studies were pooled, the reduction was 0.124 mmol/L (4.80 mg/dL). The LDL-cholesterol reductions were 0.132 mmol/L (5.10 mg/dL) and 0.158 mmol/L (6.11 mg/dL) when the meta-analysis was restricted to those studies in which at least 45 g of almonds were consumed per day and in which the subjects had elevated LDL-cholesterol levels at baseline, respectively.
The researchers noted that although the mechanism for cholesterol reduction is not fully understood, the composition of almonds - which includes a favorable fatty acid profile (high in mono- and polyunsaturated fats and low in saturated fats), nutrient composition (containing 6 grams of plant protein and 4 grams of dietary fiber per ounce (28 grams), plus other key constituents like flavonoids and sterols) - may all play a role in their favorable effects on blood lipids.
Moreover, the researchers noted in their review that there were significant reductions in body weight with the almond interventions relative to the control in three of the studies analyzed. The authors drew attention to the study by Berryman et al., in particular, which was a rigorously controlled diet study in which all of the foods were provided during both the almond and control intervention periods. Participants experienced significant improvements in body weight, waist circumference and body composition (including abdominal fat mass) with 6 weeks of an almond diet vs. a control diet. The authors of the meta-analysis noted that these observations of improvements in body weight and composition are consistent with the finding by Novotny et al. (2012) that not all of the energy in almonds is actually metabolizable4. It is important to recognize that maintaining a healthy weight, along with consuming a healthy diet, are lifestyle factors that can help promote heart health.
The health benefits of almonds have been well-established in heart-healthy eating plans including the Mediterranean Diet, and reflected in current science-based dietary guidance to consume nuts regularly as part of a healthy dietary pattern.
“These results strengthen decades of research about how the regular consumption of almonds can favorably impact blood lipid levels and have a positive effect on heart health,” commented Dr. Kathy Musa-Veloso, lead author of the systematic review and meta-analysis. “The consumption of almonds as part of a healthy diet should be encouraged in order to improve blood lipid levels and reduce the risk of heart disease.” Dr. Musa-Veloso is Director of Health Claims and Clinical Trials at Intertek Scientific & Regulatory Consultancy.
A one-ounce (28 grams) serving of almonds provides 160 calories with 6 grams of plant-based protein, 4 grams of filling dietary fibre, 13 grams of “good” unsaturated fats and essential vitamins and minerals including vitamin E (50% RDA ), magnesium (20% RDA) and potassium (6% RDA).
The systematic review was conducted in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Eighteen (18) randomized controlled human intervention trials were identified that met all of the inclusion criteria and none of the exclusion criteria described below. The Almond Board of California provided funding for this scientific, systematic review. The analysis and interpretation of the data were conducted by the study authors, independently of the Almond Board of California.
Participants in all studies were adults (at least 18 years of age) without serious disease (such as heart disease). In total, across all of the studies, there were 837 participants.
Studies meeting the following criteria were included in this review:
- Human intervention study that was randomized and controlled
- Full-length article that was published in a peer-reviewed journal
- Objective of the study (either primary or secondary) was to assess the effects of almond consumption on blood lipid levels
- Amount of almonds consumed was reported
- Study duration was at least 4 weeks
- Fasting blood lipids (total, LDL-, HDL-cholesterol and/or triglycerides) were assessed
- Fasting blood lipids were measured using validated methods
Studies meeting the following criteria were excluded from this review:
- Publication was of a secondary research study (e.g., systematic review or meta-analysis)
- Objective of the study (either primary or secondary) was not to assess the effects of almond consumption on blood lipid levels
- Participants had a serious disease (e.g., heart disease, cancer) and were not representative of the general population
- Participants were children or pregnant or lactating women
- Control-adjusted effects on blood lipids could not be calculated from the data provided
- Independent effects of almonds on blood lipid levels could not be isolated (e.g., almonds were co-consumed with other nuts or another nutritional or pharmaceutical intervention)
- Study results for the same population group were published in another journal
Data collected from the studies included:
- Study design
- Location (country) of study completion
- Sample size
- Descriptions of the study population
- Proportion of males/females
- Health status
- Mean age
- Mean body mass index (BMI)
- Mean baseline blood lipid levels
- Dietary interventions
- Background diets
- Macronutrient intakes
- Mean difference in the effect for each blood lipid measure (total, LDL-, HDL-cholesterol, triglycerides, total:HDL cholesterol ratio, LDL:HDL cholesterol ratio)
- Almond intake was associated with significant reductions in levels of total cholesterol, LDL-cholesterol and triglycerides, with no significant effects on HDL-cholesterol levels.
- Across studies, the average daily consumption of almonds ranged from 20-113 g/day. Daily almond consumption was prescribed for most studies. In the two exceptions, participants were required to consume 28 g five days per week or 43 g five to seven times per week. For all studies, the almond consumption period ranged from 4 weeks to 18 months.
- According to Health Canada’s Quality Appraisal Tool for intervention studies, all included studies met the criteria for “higher quality."
- When data from all strata were pooled, the reduction in total cholesterol was 0.153 mmol/L (5.92 mg/dL), P<0.001.
- When data from only those strata for which the almond dose was at least 45 g/day were pooled, the reduction in total cholesterol was 0.212 mmol/L (8.20 mg/dL); P<0.001.
- When data from all strata were pooled, the reduction in LDL-cholesterol was 0.124 mmol/L (4.80 mg/dL); P=0.001.
- When data from only those strata for which the almond dose was at least 45 g/day were pooled, the reduction in LDL-cholesterol was 0.132 mmol/L (5.10 mg/dL); P=0.001.
- When data from all strata were pooled, the reduction in fasting triglycerides was 0.067 mmol/L (5.93 mg/dL); P = 0.042.
- When data from only those strata for which the almond dose was at least 45 g/day were pooled, the reduction in fasting triglycerides was not significant: -0.071 mmol/L (6.29 mg/dL); P = 0.114.
- For all 18 publications, the most commonly identified limitations were failure to report on allocation concealment (whether participants and researchers were aware of study group assignment), failure to report an intent-to-treat analysis and failure to report on the method of randomization (making it difficult to determine the appropriateness of the method of randomization, a factor in evaluating study quality.)
- Musa-Veloso K, Paulionis L, Poon T, Lee HL. The effects of almond consumption on fasting blood lipid levels: a systematic review and meta-analysis of randomised controlled trials. Journal of Nutritional Science 2016; 5(e34):1-15.
- Berryman CE, West SG, Fleming JA, Bordi PL, Kris-Etherton PM. Effects of Daily Almond Consumption on Cardiometabolic Risk and Abdominal Adiposity in Healthy Adults with Elevated LDL-Cholesterol: A Randomized Controlled Trial. Journal of the American Heart Association 2015; 4(1):e000993.
- In a recent study, researchers used a method different than the traditional way to measure the calories in almonds and found they have about 20% fewer calories than originally thought and that metabolizable energy content is 129 kcal per ounce. Novotny JA et al. Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets. Am J Clin Nutr 2012; 96(2): 296-301.
Good news about almonds and heart health. Scientific evidence suggests, but does not prove, that eating 1.5 ounces per day of most nuts, such as almonds, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease. One serving of almonds (28g) has 13g of unsaturated fat and only 1g of saturated fat.
About the Almond Board of California
Almonds from California are a natural, wholesome and quality food. The Almond Board of California promotes almonds through its research-based approach to all aspects of marketing, farming and production on behalf of the more than 6,000 almond growers and processors in California, many of whom are multi-generational family operations. Established in 1950 and based in Modesto, California, the Almond Board of California is a non-profit organisation that administers a grower-enacted Federal Marketing Order under the supervision of the United States Department of Agriculture. For more information on the Almond Board of California or almonds, visit Almonds.co.uk or check out California Almonds on Facebook and the California Almonds blog.