Almonds have been suggested to reduce heart disease risk by lowering total and LDL cholesterol, and exerting anti-inflammatory and antioxidant effects. Plant sterols as found in almonds may interfere with the absorption of cholesterol and bile acid, and the high amount of unsaturated fat in almonds favors an improved lipid profile, especially when this food replaces other foods high in saturated fat and refined carbohydrate. Almonds also contain phytonutrients that support the growth of beneficial gut microbes. Controlled trials have shown that general nut intake can decrease inflammation, promote healthy blood vessels, and reduce insulin resistance.
Interestingly, despite nuts being calorie-dense, research does not support a link with nut intake and weight gain. In fact, they have been associated with less weight gain and a lower risk of obesity, possibly because the fat and fiber content help to improve feelings of satisfaction and fullness.
There is limited evidence examining the intake of almonds in large populations. Smaller controlled trials have looked specifically at almonds, but larger observational studies tend to examine nuts in general, because consumption of individual nuts is relatively low in the population. Observational studies looking at intakes of nuts have found a significantly lower risk of heart disease in those eating nuts at least four times a week.  Small randomized controlled trials have found consistent benefits of diets supplemented with nuts—including almonds—on reducing total and LDL cholesterol in blood.
A large epidemiological study of health professionals that looked at general nut intake found that tree nuts including almonds eaten two or more times weekly was associated with a 13% lower risk of total cardiovascular disease and 15% lower risk of coronary heart disease.  Another large prospective study of Swedish adults found that those who ate nuts 1-2 times a week had a 12% reduced risk of a heart rhythm abnormality called atrial fibrillation, and 18% reduced risk if eaten 3 or more times a week, when compared with adults who ate no nuts.  There was also a 20% reduced risk of heart failure in those eating nuts 1-2 times a week compared with no-nut eaters.
Meta-analyses have found that a higher nut intake is associated with reduced risk of total cardiovascular disease, total cancer, and deaths from all causes. These studies had conflicting results in showing a protective effect of nut intake from diabetes, respiratory disease, stroke, and infections.
Because earlier scientific evidence suggested a heart disease benefit of eating nuts, in 2003 the U.S. Food and Drug Administration approved manufacturers to state on food labels that eating 1.5 ounces per day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.