The risk of CVD is becoming greater with the growing frequency of metabolic syndrome, the name for a cluster of risk factors that include obesity and a sedentary lifestyle, which not only raises the probability of heart disease but other health problems as well — particularly type 2 diabetes — which is beginning to reach epidemic proportions in Asian and African countries as well as Western nations.
The conditions associated with metabolic syndrome, which may soon overtake smoking as the leading contributor to CVD, present as imbalances in serum lipids (fats), including elevated levels of LDL-cholesterol (so-called bad cholesterol), reductions in HDL-cholesterol (good cholesterol) and increases in triglycerides. If these fats begin to accumulate on the walls of blood vessels, they can lead to the formation of plaque, a waxy substance that can stiffen arteries and restrict blood flow. If the plaque bursts, this can result in a blood clot leading to stroke. Other factors contributing to the development of atherosclerosis include inflammation, high blood pressure and smoking.
With time, a large number of epidemiological and interventional trials has contributed to our understanding of the nutritional, environmental and lifestyle factors that both increase and reduce the likelihood of contracting CVD. One of the more important dietary elements identified early on was the reduced prevalence of CVD in those who regularly consume fish; but, it took a detailed study of the Inuit culture and their Arctic diet to highlight the potential role of the polyunsaturated omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) in heart health.
Evidence of efficacy
The Inuit story has been cited for more than 40 years, showing that a population taking its fats mainly from seafood does not suffer from heart attack and stroke as frequently as those with a primary fat source from terrestrial animals. Subsequent interventional trials showed that the increased consumption of fish oil by various populations was associated with reductions in the incidence of major cardiac events, leading to extensive research on the physiological and biochemical mechanisms by which the omega-3 fatty acids contribute to the stabilisation or reduction of various risk factors.
Plaque formation
One controlled study that included patients with advanced atherosclerosis determined that the plaque that had developed in their arteries had been stabilized using a EPA/DHA supplement (2–3g). To understand why, it is important to appreciate how atherosclerosis can develop. Inflammation contributes significantly to atherosclerosis, from initiation throughout the progression of the disease. Inflammatory lesions on the walls of vessels can serve as anchor sites for the accumulation of cholesterol-containing low-density lipoproteins, initiating plaque build-up.
A relatively small increase in omega-3s levels significantly reduces the synthesis of inflammatory eicosanoids from arachidonic acid by the cyclo-oxygenase (COX) enzymes, which are inhibited by both DHA and EPA. In patients with carotid plaques, following the administration of an omega-3 supplement, EPA and DHA was found to actually become incorporated into the plaques, which then showed reduced signs of inflammation and structural changes consistent with greater stability.
Elevated triglycerides
Although especially threatening when combined with high levels of cholesterol, elevated triglycerides can be a warning sign on their own. Abnormally high levels of triglycerides are a signal that there is an imbalance between food intake and nutrient handling. In other words, too many calories are ingested and not enough are being used for energy. A sedentary lifestyle can contribute to elevated triglyceride levels.
A large number of controlled clinical studies have consistently demonstrated that marine omega-3 fatty acids are effective in significantly lowering the levels of serum triglycerides. A recognised treatment for extremely high levels of triglycerides (hypertriglyceridemia) is prescription forms of highly concentrated omega-3s.
Further research
Patients with diabetes typically display elevated triglyceride levels and low levels of high-density lipoprotein (HDL) cholesterol. As previous studies have shown, omega-3s reduce triglyceride levels; but, controlled studies using EPA/DHA supplements have also demonstrated an increase in HDL-cholesterol, especially in patients whose levels are low, thus addressing both risk factors for those with diabetes.
Adiponectin is a hormone produced by fat cells that regulates the metabolism of lipids and glucose and affects the response to insulin. Low levels of adiponectin are associated with obesity, type 2 diabetes and heart attack. In a clinical trial with insulin-resistant, overweight women, an omega-3 supplement (high in DHA) increased plasma levels of adiponectin when combined with a low fat diet.
Elevated blood pressure, or hypertension, imposes chronic strain on the arteries and has always been regarded as a significant risk factor for stroke, with new scientific results underscoring that it is also presents a risk for heart attacks. Recently, a meta-analysis comprising 70 controlled trials confirmed the effectiveness of omega-3 fatty acids in reducing hypertension. Owing to these and other research studies, many international regulatory bodies have allowed certain claims to be made about the benefits of regularly including EPA and DHA in diets.
Health claims
Following the accumulation of years of anecdotal evidence and successful clinical trials, the European Food Safety Authority (EFSA) has approved and supported a number of positive scientific opinions on health claims for recommended daily intake that address EPA and DHA fatty acids as a vital nutrient. The EFSA has allowed the following claims related to cardiovascular health:
- EPA and DHA contribute to the normal function of the heart; a beneficial effect is obtained with a daily intake of 3g of EPA/DHA
- EPA and DHA contribute to the maintenance of normal blood pressure; a beneficial effect is obtained with a daily intake of 3g of EPA/DHA
- EPA and DHA contribute to the maintenance of normal blood triglycerides level; a beneficial effect is obtained with a daily intake of 2g of EPA/DHA
- DHA contributes to the maintenance of normal blood triglycerides level; a beneficial effect is obtained with a daily intake of g of EPA/DHA.
And, recently, the United States Department of Agriculture (USDA) and Health and Human Services (HHS) announced the release of the 2015–2020 Dietary Guidelines for Americans (DGA). It was recommended that, for the general population, the consumption of about eight ounces per week of a variety of seafood is associated with reduced cardiac deaths among individuals with and without pre-existing CVD. These claims further validate what years of research in animal and human trials have shown — marine omega-3 fatty acids play an integral role in the reduction of CVD.
Conclusion
Cardiovascular disease continues to make a significant impact around the world. It can develop through a number of risk factors including elevated levels of LDL-cholesterol and triglycerides, diabetes and hypertension. Years of epidemiological studies and numerous clinical trials have consistently pointed to a role for omega-3 fatty acids to address the risk factors related to CVD. Because of the overwhelming body of research, EFSA has allowed various claims to be made regarding the health benefits of EPA and DHA in preventing cardiovascular diseases.
In addition, the USDA has emphasised the importance of seafood consumption for its efficacy in reducing cardiac deaths. While the research has been validated, getting enough seafood might not be an option for all consumers and, as such, manufacturers have developed a selection of supplements to choose from, many of which are specially formulated to address a number of health concerns.
In regards to cardiovascular health, certain concentrations of omega-3 supplements have been proven to be effective in controlled clinical studies to reduce the risk factors that contribute to CVD. Many of these studies utilised a 2–3g EPA/DHA supplement. At FMC, we have developed a variety of condition-specific omega-3 concentrations, including the EPAX 6000 TG/TGN, a highly concentrated product in an EPA/DHA ratio that meets this qualification and has been proven in a number of research studies to be effective in the support of cardiovascular health. In addition to providing support for various health concerns, it’s important that all omega-3 products meet global standards for transparency, purity and sustainability. By emphasising responsible corporate practices, suppliers and manufacturers of omega-3 products can support the health and well-being of both consumers and the environment.