Almond (Prunus dulcis, Rosaceae) intake has been associated with epidemiological studies and meta-analyses of clinical trials with possible health benefits including possible reduction in the risk of cardiovascular diseases. Studies suggest oleic acid, phenolic acids, phytosterols, and phytochemicals in almonds contribute to their cardioprotective qualities. These authors reported on the extension of a randomized, controlled trial, from 16 to 20 weeks, to investigate the effects of daily almond intake on body composition and blood lipid profiles in healthy young adults. They gathered data at four-time points to evaluate the time and interaction effects of almond intake on cardiovascular parameters. Data from baseline and week 20 are reported.
The study participants described here were engaged in the original 16-week study. The 169 participants were nonsmokers, aged 20-39 years, had no clinical symptoms, and had no significant body weight change during the preceding six months. Their body mass index (BMI) range at baseline was 17-30 kg/m2. The current study adds to the original study, with 85 of the 169 study members continuing for an additional four weeks. Participants were evaluated at baseline and after weeks eight, 16, and 20. The 57 individuals in the almond group consumed 56 grams of almonds daily; the 28 individuals in the control group consumed high-carbohydrate control foods with a similar number of calories as the almonds. The study participants were instructed to continue their usual physical activity and to avoid any additional nuts or nut products. Three-day diet records were assessed at baseline and during the last week of the study.
Individuals with a compliance rate of less than 80% were dropped from the study.
Anthropometric measures included waist and hip circumference, weight, blood pressure, and analyses of body composition (total body water, protein, and body fat mass), muscle and fat (body weight, skeletal muscle mass, and body fat mass), and obesity (body fat percentage and BMI). Fasting blood samples were collected at baseline and after weeks eight, 16, and 20 to measure levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and very LDL-C (VLDL-C). No between-group baseline differences were observed for anthropometric and body composition measurements. Significantly lower baseline levels of TG (P=0.001), TC (P=0.041), LDL-C (P=0.024), non-HDL-C (P=0.020), and VLDL-C (P=0.001) were found in the control group compared with the almond group.
After 20 weeks, the individuals in the almond group were eating significantly greater amounts of vegetable protein (P=0.000), fiber (P=0.000), vitamin E (P=0.000), riboflavin (P=0.000), phosphorus (P=0.004), magnesium (P=0.000), monounsaturated fatty acids (MUFAs, P=0.000), and polyunsaturated fatty acids (PUFAs, P=0.000) compared with baseline. The change in energy intake from baseline to week 20 was not statistically significant in that group (P=0.136). After 20 weeks, the control group members had significantly higher energy intake (P=0.015) and consumed more carbohydrates (P=0.021) and total fat (P=0.000) compared with baseline.
Total protein intake was similar between the two groups at baseline; however, after week 20, the intakes of carbohydrates (P=0.006), animal protein (P=0.028), and cholesterol (P=0.022) in the almond group were lower compared with the control group. Intakes of vegetable fat (P=0.000), vegetable protein (P=0.005), fiber (P=0.000), vitamin E (P=0.000), riboflavin (P=0.000), phosphorus (P=0.016), magnesium (P=0.000), MUFAs (P=0.000), and PUFAs (P=0.000) were higher in the almond group compared with the control group. Energy intake was similar between the two groups (P=0.159).
In the almond group, waist circumference decreased (P<0.0001) and body weight increased (P=0.002) during the 20 weeks compared with baseline. Levels of TC (P<0.0001), HDL-C (P<0.0001), TC:HDL-C (P=0.048), LDL-C (P<0.0001), non-HDL-C (P<0.0001), TG (P<0.0001), and VLDL-C (P<0.0001) were significantly lower after 20 weeks compared with baseline. HDL: LDL-C significantly increased after 20 weeks (P=0.004). Total body protein, fat-free mass, soft lean mass, skeletal muscle mass, and basal metabolic rate significantly increased after 20 weeks compared with baseline (P<0.0001 for all). Diastolic blood pressure decreased significantly after 20 weeks (P=0.12). In the control group, compared with baseline, body weight (P<0.0001) and BMI (P<0.0001) significantly increased, and levels of TC (P<0.0001), TC: HDL-C (P=0.001), LDL-C (P=0.000), non-HDL-C (P<0.0001), TG (P=0.002), and VLDL-C (P=0.002) were significantly reduced.
No significant between-group changes were seen in weight after 20 weeks. Compared with the control group, subjects in the almond group experienced significantly greater reductions in TC (P<0.0001), HDL-C (P=0.033), LDL-C (P=0.000), non-HDL-C (P=0.001), TG (P=0.000), VLDL-C (P=0.000), and body fat percentages (P=0.015) after 20 weeks. Body fat mass (P=0.027) and waist-hip ratio (P=0.035) increased significantly more in the control group than in the almond group after 20 weeks. Using a mixed model, the authors analyzed the time, intervention, and interaction effects throughout the study. Significant interaction effects were observed for the changes in TC (P=0.009) and non-HDL-C (P=0.030). Significant group effects were seen for changes in HDL-C (P=0.008), TC: HDL-C (P=0.016), HDL: LDL-C (P=0.006), TG (P=0.036), and VLDL-C (P=0.036).
In this study, the effects of the dietary intervention varied by times repeated measures and changes in lipid profiles at different time points. For example, TG levels gradually decreased in the almond group throughout the trial; HDL-C levels slightly increased by week eight and then decreased by weeks 16 and 20. The control group also experienced fluctuations in lipid profile parameters, “which may indicate the duration of the intervention and measuring time point would be crucial to capture the effects of the certain intervention,” the authors write.
The study did have limitations. The isocaloric control foods contained higher percentages of carbohydrates compared with almonds, so the macronutrient composition of the control foods and that of the almonds did not match. The almonds and control foods could not be blinded. Also, because individuals with compliance rates of less than 80% were dropped from the study, the authors could not conduct an intent-to-treat analysis.
The authors concluded “the effects of almond appeared differently when using times repeated measures and the changes of lipid profiles achieved at different time points. Continuous consumption of almond for 20 weeks may improve serum lipid profiles and body composition in healthy young adults.”
The authors declare no conflicts of interest.
Liu Y, Hwang HJ, Kim HS, Park H. Time and intervention effects of daily almond intake on the changes of lipid profile and body composition among free-living healthy adults. J Med Feed. 2018;21(4):340-347. doi: 10.1089/jmf.2017.3976.