Time and time again, studies of various demographic groups have found correlations between the consumption of nuts and lower incidence of heart disease, according to "The American Journal of Clinical Nutrition." Regardless of their reputation as a high-fat food, nuts, when consumed judiciously, can contribute to a heart-healthy lifestyle.
Biomarkers
Researchers have developed a roster of measurable biological factors, called biomarkers, that they use to determine increased risk of heart disease. Biomarkers that are specifically related to cardiovascular disorders include inflammation, oxidation and endothelial dysfunction.
Inflammation
A study of over 6,000 subjects, referenced in the "American Journal of Clinical Nutrition," found levels of C-reactive protein, a biomarker for inflammation, were decreased in participants who ate more nuts and seeds. Inflammation is a natural response that your immune system deploys when it senses an injury or infection. When inflammation is chronic, however, it becomes less useful as a disease fighter and turns into a complication that exacerbates cardiovascular disease.
Oxidation
A feature commonly observed in heart disease is the oxidation of lipoprotein, a type of carrier protein that conveys cholesterol through the bloodstream. Nuts contain both monounsaturated and polyunsaturated fats. According to AJCN, nuts that contain monounsaturated fats may improve oxidative status, while the effects of nuts with polyunsaturated fats on oxidation is negligible. Almonds are an example of nuts high in monounsaturated fat, while walnuts contain more polyunsaturated fat.
Endothelium
Walnuts have been studied for their effects on the tissue that lines the inside of the heart and blood vessels, which is referred to as endothelium. ACJN states that walnuts have demonstrated beneficial effects on blood vessel reactivity, as well as the potential for improving endothelial function.
Lower Cholesterol Levels
In addition to biomarker-based evidence that nuts decrease heart disease risk, their ability to lower cholesterol levels also indicates cardiovascular benefits. Nuts contain several types of fat that help to lower your cholesterol levels. MayoClinic.com explains that the mechanisms by which the monounsaturated and polyunsaturated fats found in nuts decrease your level of "bad" LDL cholesterol are not fully understood. The presence of omega-3 and omega-6 fatty acids is thought to be related to these decreases in LDL, but Rogelio U. Almario of the Department of Internal Medicine at the University of California at Davis notes that these fatty acids seem to have varying metabolic effects depending on whether they're derived from walnuts or from cooking oil.
Amounts
If you're interested in consuming nuts to decrease your risk of heart disease, MayoClinic.com recommends that you limit your intake to about a handful, or 1.5 oz., daily. Walnuts, almonds, hazelnuts and pistachios are among the recommended varieties.
References
- MayoClinic.com; Nuts and Your Health; Eating Nuts for Heart Health; February 2011
- "The American Journal of Clinical Nutrition"; Effects of Walnut Consumption on Plasma Fatty Acids and Lipoproteins in Combined Hyperlipidemia"; Rogelio U. Almario, et al.; July 2001
- "The American Journal of Clinical Nutrition"; Nuts and Novel Biomarkers of Cardiovascular Disease; Emilio Ros; 2009
