Dietary hempseed may improve cardiac tissue function
The authors of this featured study sought to determine the potential effects of dietary hempseeds on cardiac ischemia-reperfusion injury. Investigators noted a body of research that has already established positive cardiovascular effects following consumption of one major type of polyunsaturated fatty acid (PUFAs): omega-3 oils. Research is less conclusive as to whether the second common form of PUFAs, omega-6, are also cardioprotective. Al-Khalifa et al note recent studies suggesting the importance of the ratio of omega-6 to omega-3 fatty acids, the two most predominant forms being linoleic acid (LA) and a-linolenic acid (ALA), respectively. While the standard American diet has an increased ratio of LA to ALA, in contrast, hempseeds are high in both and possess a ratio closer to the postulated ideal of ~3:1. Researchers in this study hypothesized that this ideal ratio of omega-6 and omega-3 oils in hempseeds would positively alter the response of heart tissue to ischemia reperfusion injury.
In accordance with the Canadian Council on Animal Care, male Sprague-Dawley rats were fed a standard rat meal supplemented with either 5%(5H) or 10%(10H) hempseed, palm oil (SF) – high in saturated fatty acids – or a control of 10% (DLH) dilapidated hempseed. At the conclusion of 12 weeks, rats were anesthetized to allow hearts to be removed for in vitro perfusion. Ischemia was induced, followed by a period of reperfusion in order to assess the contractile performance of the heart tissue. Using gas chromatography, the fatty acid content of plasma was assessed for the presence and concentration of LA, ALA and g-linolenic acid (GLA) - hempseeds are also known as a source of GLA. For the above and other data measured, statistical significance was determined at P < 0.05.
Among several notable findings, researchers observed a "selective absorption" of ALA and GLA omega-3 oils over the omega-6 fatty acid, LA. Hempseed is enriched in all three fatty acids, but most especially in LA. Despite the relatively higher levels of LA over ALA or GLA in hempseeds, in the hempseed supplemented groups researchers noted a significant increase in plasma ALA and GLA, and not LA. Al-Khalifa observed that increases in these fatty acids accounted for an elevated concentration of only ALA in cardiac tissue. They acknowledge their research “is the first report that these omega-3 fatty acids are effectively absorbed and then selectively deposited within the heart with hempseed supplementation of the diet.” Cardiac performance during ischemia-reperfusion was assessed using a number of parameters, including "developed tension, resting tension, the rates of tension development and relaxation, and the number of extrasystoles." The 5H and 10H groups showed significant improvement in a number of measures, while the SF group showed a decline in heart tissue function. Not only did Al-Khalifa et al’s study establish that dietary hempseed significantly elevates levels of ALA in heart tissue, they were the first to demonstrate that hempseeds confer cardioprotective effects in heart tissue under "ischemia-reperfusion challenge." Their study clearly identifies ALA from hempseeds as responsible for the beneficial effects observed.
Study: Al-Khalifa, A., et al, Am J Physiol Regul Integr Comp Physiol 292: R1198-R1203, (2007)