There are very few things that have been hotly debated in the nutrition world as aggressively and for as long as dietary fat and the influence that this has on the cardiovascular system. The traditional view posited that all fats, particularly saturated fats, were detrimental to heart health. However, emerging research suggests the relationship between dietary fat and cardiovascular health is more nuanced, depending on the type of fat, the overall dietary context, and individual health conditions.You probably know many of my positions on this, but some of these newer findings may surprise you.
Let’s start with the most surprising and controversial of all.
Saturated Fat - it’s not all black and white.
If I were to ask you what is the most damaging thing to cardiovascular health, I would lay a bet that most of you would say ‘saturated fat’. It has been the dietary devil for decades. It was the focal point of every healthy eating campaign in the 80’s and 90’s.
Then in recent times with the rise of things like the Atkins diet and keto, it has suddenly been consumed in abandon and branded as completely harmless.
So what gives? Well, contrary to long-standing beliefs, recent studies indicate that saturated fat may not be as problematic for cardiovascular health when consumed as part of a low-carbohydrate diet. The PURE study, a large multinational cohort study, reported that higher intake of saturated fat was associated with a lower risk of stroke, suggesting that the effect of saturated fat on cardiovascular health might depend on the overall macronutrient composition of the diet (Dehghan et al., 2017).
Another meta-analysis found no clear evidence that dietary saturated fat is associated with an increased risk of coronary heart disease or cardiovascular disease (Chowdhury et al., 2014). These findings suggest that when saturated fats are consumed in the context of a low-carbohydrate diet, their potential adverse effects on cardiovascular health may be mitigated, possibly due to improved lipid profiles, including increased levels of HDL cholesterol (Volek et al., 2009).
Omega 6 & Trans Fats - are these the real villains?
Ok, surprise surprise, I am going to talk essential fatty acids here, and specifically Omega 6, and one of its evil twins - the trans fats. Omega-6 polyunsaturated fats and trans fats have been shown to trigger inflammation, a key factor in the development of cardiovascular disease. While omega-6 fats, found in vegetable oils like corn and soybean oil, are essential in small amounts, excessive consumption can promote inflammation (Simopoulos, 2008). This is because omega-6 fats can be converted into arachidonic acid, a precursor to pro-inflammatory eicosanoids. The balance between omega-6 and omega-3 fatty acids is crucial; a high ratio of omega-6 to omega-3 can exacerbate inflammation and increase the risk of cardiovascular disease (Simopoulos, 2002).
Trans fats, which are industrially produced through the hydrogenation of vegetable oils, are unequivocally harmful to cardiovascular health. They increase LDL cholesterol levels while decreasing HDL cholesterol, exacerbate inflammation, and are associated with a higher risk of heart disease (Mozaffarian et al., 2006). In response to this evidence, many countries have implemented policies to reduce or eliminate trans fats from the food supply.
The Omega 3 Fatty Acids - Anti-inflammatory heroes
There is a good reason that I am ever so slightly obsessed with omega 3 fatty acids in relation to almost every aspect of our health. They are powerful. They are extremely effective regulators of our physiology, especially in relation to inflammation.
The long chain omega-3 fatty acids, particularly those found in fatty fish like salmon, mackerel, and sardines, have well-documented anti-inflammatory effects that can benefit cardiovascular health. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two key omega-3 fatty acids, have been shown to reduce inflammation, lower triglycerides, and decrease the risk of arrhythmias and atherosclerosis (Kris-Etherton et al., 2002). A meta-analysis of randomised controlled trials found that omega-3 supplementation was associated with a reduced risk of cardiac death, underscoring their protective role in heart health (Aung et al., 2018).
Oleic acid - the Mediterranean molecule with a long standing track record
If you have read much on the benefits of the Mediterranean diet, you will know that it has a long standing reputation for being heart healthy, and olive oil has been identified as a key contributor to these cardiovascular benefits. What is the magic that lies in olive oil? Well, firstly a good extra virgin olive oil is packed with polyphenols that protect blood vessels from damage, but it also contains ‘Olieic Acid’ - an omega 9 fatty acid.
Oleic acid, a monounsaturated fat predominant in olive oil, avocados, and nuts, is another dietary fat with positive implications for cardiovascular health. Consumption of oleic acid has been linked to reduced inflammation, improved lipid profiles, and lowered blood pressure (Massaro et al., 2008). The PREDIMED study, a landmark clinical trial, demonstrated that a Mediterranean diet rich in oleic acid from olive oil and nuts significantly reduced the risk of major cardiovascular events among individuals at high cardiovascular risk, highlighting the heart-healthy benefits of oleic acid and related unsaturated fats (Estruch et al., 2013).
The relationship between dietary fat and cardiovascular health is complex and influenced by the type of fat, dietary composition, and individual health status. While saturated fats may not be inherently harmful in the context of a low-carbohydrate diet, the consumption of omega-6 and trans fats in excess is associated with increased inflammation and cardiovascular risk. Conversely, omega-3 fatty acids and oleic acid offer anti-inflammatory and heart-protective benefits. It's clear that the quality of dietary fats matters immensely for cardiovascular health, and understanding the nuances can guide more effective dietary choices.
References
Aung, T. et al. (2018). 'Associations of Omega-3 Fatty Acid Supplement Use With Cardiovascular Disease Risks'. JAMA Cardiology, 3(3), 225-234.
Chowdhury, R. et al. (2014). 'Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk'. Annals of Internal Medicine, 160(6), 398-406.
Dehghan, M. et al. (2017). 'Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study'. The Lancet, 390(10107), 2050-2062.
Estruch, R. et al. (2013). 'Primary Prevention of Cardiovascular Disease with a Mediterranean Diet'. The New England Journal of Medicine, 368, 1279-1290.
Kris-Etherton, P.M. et al. (2002). 'Fish Consumption, Fish Oil, Omega-3 Fatty Acids, and Cardiovascular Disease'. Circulation, 106(21), 2747-2757.
Massaro, M. et al. (2008). 'The Mediterranean diet: the reasons for a success'. Thrombosis Research, 121(3), 401-404.
Mozaffarian, D. et al. (2006). 'Trans Fatty Acids and Cardiovascular Disease'. The New England Journal of Medicine, 354, 1601-1613.
Simopoulos, A.P. (2002). 'The importance of the ratio of omega-6/omega-3 essential fatty acids'. Biomedicine & Pharmacotherapy, 56(8), 365-379.
Simopoulos, A.P. (2008). 'The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases'. Experimental Biology and Medicine, 233(6), 674-688.
Volek, J.S. et al. (2009). 'Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome'. Progress in Lipid Research, 48(5), 304-317.
