A new study published in the British Journal of Nutrition found that participants who ate almonds as part of a heart-healthy diet significantly improved certain factors associated with heart disease risk.[i] Researchers estimated that for every 30 grams increase (approximately 1 ounce) of almonds consumed daily during the study, study participants' estimated 10-year coronary heart disease (CHD) risk score was reduced by 3.5%.
The randomized, controlled clinical study, conducted by researchers at the University of Toronto, included 27 adult participants (mean age of 64 years) with elevated LDL cholesterol. Participants followed a diet low in saturated fat and cholesterol that also included each of three dietary interventions for four weeks each in a crossover design.
Each day for four weeks, researchers gave one group 50-100 grams (2-4 ounces) of almonds. A control group received 100-200 grams of muffins, and a third group received 25-50 grams (1-2 ounces) of almonds plus 50-100 grams of muffins. Each participant completed all three dietary treatments, so the total length of the study was 12 weeks.
The quantity of almonds and muffins provided to each participant varied according to estimations to maintain his or her baseline weight. The muffins were formulated to provide the same number of calories and the same amount of saturated fat (SFA), polyunsaturated fat (PUFA), protein and fiber as the almonds. The primary difference between the almond composition and the muffin composition was that the almonds had significantly more monounsaturated fat (50% vs 8% of calories), whereas the muffins had significantly more carbohydrates (53% vs 15% of calories).
In the triglyceride fraction, oleic acid and total MUFAs increased significantly in a dose-dependent manner with almond consumption compared to muffins. Increased oleic acid and MUFA content of the serum triglyceride was inversely associated with CHD lipid risk factors and overall estimated 10-year CHD risk.
Previously published data on this same group of people showed that total cholesterol and LDL, or "bad," cholesterol decreased, and HDL, or "good," cholesterol increased, in the almond group compared to the control group.[ii]
"The favorable effect of almonds, particularly the monounsaturated fat component, on heart disease risk in this study is consistent with previous research, including Mediterranean diet research," said Cyrill Kendall, PhD, research associate at University of Toronto and the Clinical Nutrition and Risk Modification Center at St. Michael's Hospital, and the study's principal investigator. "The improvement in serum fatty acid profiles observed with almond consumption provides further support for a diet rich in monounsaturated fats for overall cardiovascular health."
A hallmark of the Mediterranean diet is the consumption of MUFA-rich olive oil.[iii] Almonds also contain a high proportion of MUFAs, providing 9 grams per 1 ounce serving (or about 50% of their total calories).
And overall, the nutrient profile of almonds - low on the glycemic index and providing a powerful nutrient package including hunger-fighting protein (6 g/oz), filling dietary fiber (4 g/oz) and important vitamins and minerals such as vitamin E (7.3 mg/oz), magnesium (77 mg/oz) and potassium (200 mg/oz), makes them an ideal fit in a heart-healthy [iv] lifestyle.
This study comes on the heels of a large-scale review from researchers at Harvard University encompassing 27 studies (16 from North America, 8 from Europe and 3 from Asia) and more than 500,000 adult participants (mean age 53 years) which showed that eating four servings (1 ounce) of nuts weekly was associated with 24% lower risk of fatal heart attacks, 22% lower risk of non-fatal heart attacks and 13% lower risk of diabetes.[v] Although the study was observational in nature, relied on self-reported dietary intake which did not account for nuts consumed as an ingredient, and included relatively few studies per disease state, it adds to the strong body of evidence supporting the consumption of nuts like almonds as part of a heart-healthy dietary pattern.
Nearly two decades of research shows that almonds can help maintain a healthy heart and cholesterol levels. The Food & Drug Administration has noted, "Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts including almonds as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."
Design: The study was a randomized, controlled clinical trial that evaluated the effects of almond consumption on serum fatty acid composition and estimated 10-year risk of coronary heart disease (CHD). Study participants were 27 adult men and women (mean age: 64 years) with elevated LDL cholesterol (mean 167 mg/dL) but were otherwise healthy. For four weeks, subjects consumed a National Cholesterol Education Program (NCEP) Step 2 diet along with 50 - 100 g/day (approximately 2-4 oz.) of almonds (full-almond dose); 100 to 200 g/day of muffins (control); or 25 to 50 g (~1-2 oz.) of almonds plus 50-100 g/day of muffins (half-almond dose).
The muffins were formulated to have a similar nutritional composition as the almonds with the exception of carbohydrates and fat, as the muffins' carbohydrate content was increased to balance the calories from monounsaturated fatty acids in the almonds. Almond and muffin intake amounts were based on estimated energy requirements of each subject, and provided an average of 423 calories per day. The study was crossover in design, with each subject completing all three four-week dietary treatments in random order, with a washout period of at least two weeks in between. The primary objective of the study was to assess the effects of almonds on blood lipids, which have been previously published; these results are secondary analyses.
Results: Compared to eating muffins, eating almonds was associated with a significant increase in the oleic acid and MUFA content of serum triglycerides. In the free fatty acid fraction, eating almonds also increased oleic acid and MUFAs, although the results just missed significance in the full-dose almond group, which researchers attribute to higher variability. For every 30 g/day (approximately 1 oz.) increase in the intake of almonds, the estimated 10-year risk score of CHD was reduced by 3.5% for study participants. No significant associations were observed between PUFAs and 10 year CHD risk. There were no significant differences in body weight between groups.
Conclusion: Eating almonds as part of a heart-healthy diet had favorable effects on serum fatty acid profiles, which were associated with reduced risk of coronary heart disease. These data are consistent with the large body of evidence in support of the heart health benefits of almond consumption.
Limitations: 10-year risks of CHD were estimated indirectly based on the Framingham equation. Each dietary intervention period was relatively short at four weeks, and there was a relatively high drop-out rate. 37.2% of the subjects who were randomized did not complete the entire study, and therefore were not included in the final analysis. In addition, almond consumption was associated with an increase in fecal excretion of MUFAs (unpublished data reported by the authors); thus, the effects may be confounded by differences between the dietary intervention periods in the actual amounts of nutrients and energy that were absorbed.