Introduction
The consumption of fat, one of the main macronutrients, has long been popularly associated with obesity and cardiovascular disease. However, this generally accepted premise fails to discriminate among the several types of fat: saturated fats, trans- fats, monounsaturated fats and polyunsaturated fats. Thus, this statement comprises all fats regardless of the essential differences in structure among them, but is it accurate that all categories of fat in the diet carry the same health risk? This paper aims to answer this question.
Summary
The first type of fat to be analyzed in this paper is trans-fat, also known as trans-fatty acids (TFA), commonly found in margarine, snacks, fast food, among others. This paper will base its judgment of trans-fats on a review paper developed by Mozaffarian, Aro and Willet titled “Health effects of trans-fatty acids: experimental and observational evidence”. The researchers aimed to study the evidence that suggests a relation between this type of fat and Coronary Heart Disease (CHD). Their methodology consisted on reviewing clinical publications that concerned consumption of TFA and the connection to risk factors and outcomes of CHD, focusing on evidence from controlled trials and observational studies. They recognize the flaws of both types of study individually, but agreed that the review of the data collected from both methods as a whole would allow to make reliable inferences on the issue at hand.
The review found that clinically controlled trial results suggest that TFA consumption has a negative influence over lipoproteins and blood lipids, including increased LDL-C (low-density lipoprotein cholesterol), reduced HDL-C (high-density lipoprotein cholesterol) and a total increase on their ratio and raises triglyceride levels, and very similar results were achieved through observational evidence. Moreover, the study reviewed additional health risk factors, and concluded that TFA consumption worsens insulin resistance. It is difficult to establish a fixed amount of TFA consumption in which CHD may be developed, given that for ethical reasons the conduction of further clinical trials is limited, but it is concluded through this review that consumption of this type of fat contributes to higher risk of CHD.
As for saturated fats (SFA), contained mainly in red meat, dairy and poultry, a review by Micha and Mozaffarian titled “Saturated Fat and Cardiometabolic Risk Factors, Coronary Heart Disease, Stroke, and Diabetes: a Fresh Look at the Evidence”, followed a similar methodology as the previous study, and arrived at the conclusion that compared to TFA, SFA consumption has minimal effects on the TC:LDL-C and TC:HDL-C ratios. However, it does raise LDL-C levels, for which it is generally classified as a contributor to CHD risk factors, though there does not seem to exist strong evidence to support this relation. Additionally, there is little evidence to relate SFA consumption to systemic inflammation, and while evidence is mixed on the effects over blood pressure, studies seem point that there are no direct effects over these by SFA.
As for polyunsaturated fats, mostly found in plant-based oils and foods, Mozaffarian, Micha and Wallace published a paper titles “Effects of coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials”, for which they investigated the effect of increasing PUFA consumption as a replacement for SFA, and concluded that opposite to the effect of the previously analyzed types of fat, a greater consumption of PUFA significantly reduces the risk of suffering from CHD. These findings are based on eight clinical trials in which over 13000 participants increased their PUFA intake for a year, and ultimately showed a lower risk of CHD than that of the control group.
According to the Academy of Nutrition and Dietetics, intake of monounsaturated fats (contained in a various foods and oils), known as MUFAs, has been linked to the reduction of LDL-C and triglycerides. Moreover, diets with >12% of MUFA result in lower fat mass, systolic and diastolic blood pressure. It is concluded that MUFAs as a replacement for carbohydrates and SFAs is beneficial for overall health.
Conclusions
Literature review on the effects of different types of fats over health, more specifically cardiovascular conditions but also evaluating insulin resistance and fat mass, it is evident that these effects vary greatly depending on the type of fat consumed. Evidence suggests that consumption of trans-fats, or TFAs increases risk of CHD, and the same is suspected of saturated fats, though not strongly proven. Conversely, monounsaturated and polyunsaturated fats seem to actually be beneficial for human health, as their consumption lowers cholesterol levels effectively reducing the risk of CHD.
The study of the effects of this macronutrient discriminated by its different types is related to a nutrition course given that this science studies the interaction of nutrients on the organism, and ultimately seeks to encourage healthy dieting as a method for disease prevention and overall well-being.
Works cited:
Academy of Nutrition and Dietetics. «Position of the Academy of Nutrition and Dietetics: Dietary Fatty Acids for Healthy Adults.» Journal of the Academy of Nutrition and Dietetics (2014): 2212-2672.
Micha, Renata y Dariush Mozaffarian. «Saturated Fat and Cardiometabolic Risk Factors, Coronary Heart Disease, Stroke and Diabetes: a Fresh Look at the Evidence.» Lipids (2010): 893-905.
Mozaffarian, D: Aro, A: Willet, W. «Health effects of trans-fatty acids: experimental and observational evidence.» European Journal of Clinical Nutrition (2009): 63, S5-S21.
Mozaffarian, Dariush, Renata Micha y Sarah Wallace. «Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.» Plos Medicine (2010).
