Heart Disease is one of the most common causes of premature death, yet diet-related and preventable.
Advice to eat vegetable oils and margarines rich in polyunsaturated fatty acids instead of butter and limit other animal fats rich in saturated fats such as meat and dairy products has been the cornerstone of global dietary guidelines for decades. These recommendations were made to reduce the risk of heart disease, yet fifty years later, updated research shows no evidence of cardiovascular benefits.
Subsequent studies since the 1970s have reported that polyunsaturates from marine oils, namely omega-3s, are very heart protective. At the time of the original work, the difference between these omega3 polyunsaturates and the vegetable oil omega-6s was not well understood. Indeed, it was generally perceived that all fats were harmful, giving rise to the popularity of low-fat diets. The consequences of propagating this belief are currently rife, as diet-related diseases reach epidemic levels.
Recent media interest has put the spotlight on the fat controversy, changing public perception that not all fats are bad, and whilst some are harmful, there are indeed some very beneficial fats. Scientific consensus that omega3 fish-oils promote wellbeing, particularly for cardiovascular and brain health, as well as to combat inflammatory disorders, has driven the popularity of sales of fish-oil supplements.
Whilst the clear benefits of increasing intakes of omega-3 fish-oils are gaining understanding, the balance or ratio in the diet between omega-6s to omega-3s, still lurks within the research domain.
The bottom line is that the misplaced confidence in vegetable oils has resulted in too much omega-6 and not enough omega-3 in the diet.
Increasing polyunsaturated fats from vegetable oils in order to reduce risk of heart disease has driven omega-6 levels fifteen to twenty-five times higher than omega-3 levels, where our ancestors had an approximate equal balance. Eating too little omega-3 and to much omega-6 has had very harmful consequences to health, because the two groups fats are metabolically and functionally distinct, and often have opposing biological effects.
Omega-6 and omega-3 are the parent compounds for the production of eicosanoids, a vast group of biological compounds which act as hormone-like messengers that mediate a cascade of extensive biochemical and physiological reactions including inflammation, blood clotting, pain, immune functions, blood pressure and regular heart beat.
Omega-3 fats(EPA and DHA) from fish or fish oil are heart friendly because they
- decrease production of prostaglandin E2 (PGE2) metabolites where the drugs aspirin and ibuprofen work to keep pain, inflammation and blood clotting at bay
- decrease platelet aggregation which causes blood to become sticky and clump, thus reduce tendency of clot formation and obstructions in blood supply which increase risk of strokes, embolisms and infarction
- decrease production of leukotrienes which promote inflammation and white blood cells to trigger plaque formation
- promote vasodilation that keeps blood vessels open and lowers blood pressure
- safeguard against cardiac arrhythmia.
The metabolic children of omega-6s promote heart disease and are harmful to overall health and wellbeing. Omega-6s produce thromboxanes which promote blood clotting, platelet stickiness and vasoconstriction which narrows blood vessels and increases blood pressure. Other eicosanoids from omega-6 including interleukins stimulate the inflammatory response and promote white cells to form free radicals which cause oxidation of blood fats and damage leading to the formation of atheroma, thrombus, blocked and narrowed arteries. New research has found that when omega 6s are high in arterial plaques, the plaques are more likely to burst. Oxidised or ‘rusted’ vegetable oil particles found in LDL are very harmful, and a valid mechanism may be that these damaged omega-6s create very potent bioactive compounds that stimulate inflammation without having to go through the eicosanoid pathway. In simple terms, the excess vegetable oils in the lipoproteins are themselves causing the inflammation that triggers damage which initiates the formation of plaques. Smoking and drinking also creates a lot of free radicals that rust up these blood fats.
A diet rich in omega-6 fats shifts the physiological state to one that is proinflammatory and prothrombotic. No wonder populations rely on anti-inflammatory and blood thinning drugs like ibuprofen and aspirin.
Because of the increased amount of omega-6s in the Western diet, larger quantities of metabolic products from omega-6 are produced than those formed from omega-3s. Since both families of fats share the same biochemical pathway, they share the conversion enzymes and if you use the analogy of omega-6 and omega-3s as opposing football teams, the omega-6 players outnumber the omega-3 players and omega-6 hogs the ball and scores all the unhealthy goals.
The simple answer lies in correcting the imbalance, by increasing the intake of omega-3, especially the fish-oils EPA and DHA, whilst simultaneously decreasing the intake of commercial vegetable oils and margarines and all the processed and packaged foods containing them.
However, vegetarians and vegans take note that the excess intake of omega-6 compared to deficiency in omega-3 can inadvertently occur, even in natural wholesome diets, as most nut and seed oils are relatively rich in omega-6, with only few oils rich in omega-3 such as flax oil, or to a lesser extent hemp, rapeseed, chia, pumpkin or walnut oils. Notably, vegetable omega3 sources do not provide a direct source of the more heart-friendly omega-3 EPA and DHA which are only obtained by eating oils of marine origin. Conversion of simple vegetable source omega-3 to longer chain and greater degree of unsaturation is considered poor.
Olive oil is a good choice as it predominantly contains omega-9, which does not interfere with the balance by avoiding excessive omega-6 intake.
The current bottom line is that omega-3 fish oils have reached superstar status as scientific understanding has undisputedly deciphered the biochemical pathways and physiological mechanisms by which omega-3 DHA and EPA bestow their gifts of optimising cardiovascular health.
The theory that eating fish may safeguard and prevent against cardiovascular disease can safely be put into practice. Be sure to up your intakes of EPA and DHA.
BMJ 2013 Feb 4;346:e8707 Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis.
Written by: Babi Chana BSc (HONS) BSc Nut.Med BANT. CHNC – Nutritionist for Wiley’s Finest Wild Alaskan Fish Oil.