Are anthropometric biomarkers, nutrient intake and blood fatty acid composition associated with the electrical activity of the heart in a sample population of healthy women?

Cardiovascular disease (CVD) is a significant global burden. Obesity is considered a major causative factor in its development, and a poor diet with a positive energy balance is the main cause of obesity. Fatty acids (FAs) are a vital aspect of the human diet, and polyunsaturated fatty acids (PUFAs), particularly those from the n-3 family, are considered to bestow the most beneficial effects in the human body. This study was designed to investigate whether anthropometric biomarkers, nutrient intake and blood FA composition were associated with the electrical activity of the heart in a sample population of women, to support a link between FAs and cardiac function. Laboratory testing on 23 participants involved gathering anthropometric data, electrocardiograms (ECGs), and capillary blood samples, plus 4-day food diaries. Dietary analysis was used to quantify intakes of FAs and other macronutrients, ECG parameters were measured, and FA methylation and gas chromatography were used to determine blood FA levels. Associations between all variables were tested for statistical significance. There were some positive associations found between markers of obesity and disruption of the cardiac conduction system. Different measures of total saturated fatty acid (SFA) were associated with negative effects on the electrical activity of the heart, although some individual SFAs were seen to correlate with blood pressure in ways that suggested positive effects. The ratio of n-6:n-3 PUFAs was positively associated with the area under the curve (AUC) of the QRS complex and the R wave amplitude of the ECG - both measures of ventricular depolarisation - suggesting that a high n-6:n 3 PUFA ratio is detrimental to ventricular function. A negative relationship was found between docosahexaenoic acid (DHA), an important individual n-3 PUFA, and the AUC of the QRS, suggesting a beneficial effect of DHA on ventricular depolarisation. Although causation cannot be confirmed, these results are likely due to the pivotal role that PUFAs play in cell membranes, and particularly in the efficient function of cardiac ion channels, but also in the reduction of chronic inflammation. PUFAs of both the n-6 and n-3 families are essential nutrients and as such must be taken in in sufficient quantities in the diet. Intakes of n-3 are low in many countries and public health messages aimed at reducing CVD prevalence must focus on reducing SFA consumption and increasing n-3 PUFA intake so that the ratio of n-6:n-3 is, at most, 5:1.