Higher Circulating Levels of Long-Chain Omega-3 Associated with Lower Incidence of Heart Failure
Mozaffarian , D. et al., Annals of Internal Medicine, 155: 160-170 , 2011
Harvard School of Public Health, Boston, MA, USA
The primary focus of the present study was to determine if higher blood levels of the long-chain omega-3 fatty acids as EPA/DPA/DHA in a large number of adults who were free of heart disease at entry may show a relationship to their risk of developing congestive heart failure (CHF) with time. For this purpose, 2735 US adults aged 65 years and over (average age of 75 years, both genders) were randomly selected who were free of heart disease when recruited. Blood samples were taken and the fatty acid compositions (including omega-3 fatty acids) were determined in the blood serum phospholipid – a recognized biomarker for omega-3 status . This biomarker reflects the dietary intake of long-chain omega-3 fatty acids (eg, from fish/seafood) and the intake and the somewhat limited conversion of dietary alpha-linolenic acid omega-3 to the long-chain omega-3 fatty acids as EPA (eicosapentaenoic acid) plus DPA (docosapentaenoic acid) plus DHA (docosahexaenoic acid).The subjects were followed for 10 years by annual clinical examinations and interim phone calls. Appropriate clinical criteria for confirming a diagnosis of CHF were employed.
After adjusting for various factors (age, gender, diabetes, physical activity, body mass, others), higher long-chain omega-3 levels in the circulation (measured in serum phospholipid) were found to be associated with a much lower likelihood of developing CHF over the next several years. At seven years for example, those subjects having EPA levels in the highest quartile (top 25 %) exhibited a 52 % lower risk for developing CHF when compared to those in the lowest quartile (lowest 25 % with respect to EPA levels). Those in the highest quartile with respect to circulating levels of DPA , DHA, and total long-chain omega-3 (sum of EPA plus DPA plus DHA) exhibited corresponding lower risks for developing CHF of 39 %, 36 %, and 49 %, respectively. The authors concluded that higher circulating levels of each of the three individual long-chain omega-3 fatty acids and their sum are associated with a lower incidence of CHF in older adults.
This extensive population-based study supports recent population and intervention trials which have supported the benefits of increasing long-chain omega-3 intakes in reducing the onset of CHF and/or slowing its progression. Numerous mechanisms have been proposed by which omega-3 may exhibit their benefits in relation to heart failure as very recently reviewed by Jarreau and colleagues (Curr. Heart Failure Rep., in press (2011)). The present study from the Harvard team also indicates a considerable benefit offered by higher levels of DPA (22:5 n-3) in addition to EPA and DHA. There are other population studies which have supported a protective effect of higher levels of circulating DPA against heart disease and stroke risk. In general, dietary intakes of DPA are very low (as compared to DHA/EPA in most populations) although it can be formed in the human body to some limited extent via metabolism (desaturation and elongation reactions) from alpha-linolenic acid omega-3 as found in certain plant-based food sources. Populations such as the Inuit who consume considerable amounts of mammalian seafood (eg, seal meat) have rather high intakes of DPA as well as EPA/DHA.