Cardiovascular disease (CVD) is the major cause of death worldwide with an increasing trend in developing countries. The general risk factors associated with the diseases are known to be hypertension, smoking, and hyperlipidemia.
Worldwide, high cholesterol levels cause some 56% of ischemic heart disease and 18% of strokes, amounting to 4.4 million deaths annually. Ig has been shown that 88 mg/dL increase in fasting circulating triacylglycerol (TG) levels elevates the risk of developing CVD by 15 and 37% in males and females, respectively. A 1 mg/dL increase in the low-density lipoprotein (LDL) level is associated with a 2-3% increase in risk for CVDs, and elevations earlier in life may be associated with higher increases in risk.
High-density lipoprotein (HDL) cholesterol independently predicts CVDs as well. Every 1 mg/dL decrease in HDL-cholesterol causes a 3-4% increase in the risk. Furthermore, other indices such as cholesterol ratio or Castelli I index (ratio of total cholesterol to HDL-cholesterol) may predict CVD risk better than LDL alone. This is why modifying the lipid profile has become one of the most important goals in preventive cardiology. This can be achieved via medical therapy or adding beneficial dietary sources to daily regimen.
Many studies have suggested the beneficial effects of omega-3 poly-unsaturated fatty acids (PUFAs) on cardiovascular health. Dietary fish is a rich source of Omega-3 PUFAs. Omega-3 PUFAs come in several forms but eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been most widely investigated with regard to their cardiovascular benefits.
The American Heart Association has endorsed their nutritional value for the secondary prevention of cardiovascular events in patients with documented coronary heart disease (CHD). They recommend that patients with CHD should consume a total of 1 g per day of DHA and EPA, preferably from oily fish. However, the fish oil omega-3 supplements in the form of capsules or liquid have also been considered as an acceptable alternative. Also, supplementation of 4 g per day of omega-3 fatty acids has been considered as an approved treatment for patients with very high triglyceride levels by the FDA.
Zibaeenezhad, et al, performed a trial in which a total of 106 patients with hyperlipidemia were divided in 2 groups. One group received 2 g/day of omega-3 capsules for 8 weeks and the other group received a mean of 250 g trout fish twice weekly (for dinner and lunch) for the same period. They compared the lipid profiles of both groups after the intervention and found that their treatment with both omega-3 supplements and fresh fish caused a significant decrease in total cholesterol, non-HDL cholesterol, TG levels and total cholesterol/HDL ratio, but the reduction was more prominent in the fresh fish group.
The fish oil supplement not only had no beneficial effect on the LDL level but also worsened the situation by significantly increasing the LDL level. However, in the dietary-fish group the LDL level was significantly decreased. HDL level in both groups was increased, with the dietary fish group being more effective.
The researchers concluded that fresh fish is far better than omega-3 supplements in modifying the lipid profiles. This may be due to the fact that several important nutrients like selenium, vitamin D, and naturally occuring antioxidants are only found in oily fish and fish-oil supplements lack them. The dietary-fish can have another cardiovascular beneficial effect by consistently lowering the C-reactive protein levels, the effect which is absent from fish-oil supplements. On the other hand selenium has antithrombotic properties, reduces lipid peroxidation, myocardial infarct size and improves recovery from ischemia or reperfusion injury.
Finally, using fish in the regular diet means replacing a previous dietary component (such as red meat) with fish.
Zibaeenezhad, M.J., Ghavipisheh, M., Attar, A. et al. Comparison of the effect of omega-3 supplements and fresh fish on lipid profile: a randomized, open-labeled trial. Nutr & Diabetes 7, 1 (2017). https://doi.org/10.1038/s41387-017-0007-8