The Effect of Almonds on Coronary Heart Disease Risk Factors: Dose Response Study.

Previous studies have shown that nuts, specifically almonds, result in an improved coronary heart disease (CHD) lipid risk profile. Part of the reason has been ascribed to their high content of monounsaturated fat. However in a previous study we have done, the almond supplement, in comparison with an olive oil and dairy protein based supplement, still showed a significant reduction in total cholesterol (total-C) and low density lipoprotein cholesterol (LDL-C). We wish to use this paradigm to confirm the lipid lowering effect of almonds, to establish a similar relationship for the apolipoproteins and so add further support for the cardiovascular risk reduction associated with an almond diet. In addition, in view of the relatively high arginine content of almonds, we believe higher levels of nitric oxide (NO) will be produced, as indicated by increased NO in expired air from perfused olfactory mucosa. With this technique, we have found higher levels of NO in preliminary studies of subjects on soy diets. These data would further add to interest in nuts in relation to cardiovascular disease risk reduction. Furthermore, phenolics are present in high concentrations in oil seeds and nuts, and are known to have antioxidant activity. As yet, they do not appear to have been emphasized in relation to almonds. We will therefore determine the effect of feeding almonds on measures of oxidative stress, including oxidized LDL-C, considered to be of direct relevance to CHD; and oxidized DNA, of potential importance to neoplastic transformation and carcinogenesis.

These studies could lead to assessment of postprandial effects of almonds to determine a mechanism, and to studies of cardiovascular effects of almonds including exercise stress tests and measures of vascular reactivity (e.g. forearm blood flow) in conjunction with NO measurements.

Protocol: All subjects underwent three 4-week treatments in a randomized crossover trial.

Background Diet: Subjects were instructed to follow the National Cholesterol Education Program (NCEP) Step 2 dietary guidelines. Nuts, soy and dietary supplements (vitamins, minerals or herbal remedies) were excluded in the background diet during all phases of the study.

Treatments: The three phases were all weight maintaining, self-selected diets: control, full almond and half almond. Almond: Raw almonds were added as supplements to the subject's usual diet. Subjects with calorie needs of 2,400 kcal or greater, assessed by LRC tables, received the full almond supplement (100 g/d, approximately 600 kcal). Subjects requiring between 1,600-2,400 kcal daily received 75% of the full supplement (75 g/d, approximately 450 kcal). Subjects requiring less than 1,600 kcal daily received 50% of the full supplement (50 g/d, approximately 300 kcal). Control: The full control supplement was four 150 kcal muffins. Control supplements was matched with the energy content of the nut supplements; i.e. either 600 kcal/d (4 muffins); 450 kcal/d (3 muffins) or 300 kcal/d (2 muffins). The macronutrient composition of the muffins conformed to an NCEP Step 2 diet with 25% total fat, <7% saturated fat (by use of corn oil as the oil commonly used in healthy baked goods), with 18% protein (the average for our subject population using added skim milk powder), and zero cholesterol. Muffins were made with wheat flour. Half Portion: The Half Portion was matched with the energy content of the other two treatment periods. However on this treatment, half of the energy was derived from almonds and half from the control muffins.