Is There Something Fishy About Fish Oil?

Improvement in serum lipids and liver morphology after supplementation of the diet with fish oil is more evident under regular feeding conditions than under high-fat or mixed diets in rats

BACKGROUND

Dietary n- 3 polyunsaturated fatty acids (PUFAs) have a role in preventing cardiovascular and hepatic diseases. However, their effects might differ significantly depending on individual dietary patterns. The aim of the present study was to evaluate the effects of dietary supplementation with ω-3 fatty acids (FA), administered in different schedules, on hepatic and aortic histological structure, lipid profile, and body weight (BW) in male Wistar rats under standard (SD), high-fat diet (HFD) and mixed feeding conditions.

METHODS

PUFA treatment consisted of the administration of 50 mg/kg fish oil (FO) daily by oral gavage. HFD was obtained by adding a suspension of 4% cholesterol, thiouracil and cholic acid to the animals' drinking water. The rats were maintained on the diets for 6 weeks, and different schedules of PUFA administration were used. At 14, 28, and 42 days, the morphology of liver and aortic samples and the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG) were assessed.

RESULTS

The HFD groups exhibited significant hyperlipidemia and aortic inflammation, with progression to atherogenesis after 6 weeks. Administration of PUFAs slightly attenuated the aortic changes in these groups and reduced the liver's tendency to steatosis. FO-induced metabolic improvement was more evident in SD than in HFD rats. For instance, after the first 2 weeks, SD animals that received PUFAs had significantly increased HDL levels vs. controls (62.375 ± 4.10 vs. 52.625 ± 8.38 mg/dL, P < 0.05), but HFD rats did not, and decreased TG levels were observed exclusively in the SD rats (57.6 ± 4.09 vs. 66 ± 4.69 mg/dL, P < 0.05). After 6 weeks of n- 3 PUFA administration, LDL was significantly lower in the SD rats than in controls (13.67 ± 4.13 vs. 30.83 ± 2.86 mg/dL, P < 0.001), but the decrease in the HFD rats, although significant (49.17 ± 5.85 mg/dL vs. 57.17 ± 4.96 g/dL, P < 0.05), was not as marked. In the mixed-diet groups, administration of 50 mg/kg/day FO for 14 days under SD conditions following 4 weeks of HFD slightly decreased TG (86.625 ± 11.67 vs. 73 ± 4.52 mg/dL, P < 0.05) and increased HDL (45.875 ± 5.28 vs. 56 ± 3.16 mg/dL). However, in these animals, n-3 PUFA administration had no effect on LDL or TC. Administration of half of the above dose failed to improve any biochemical parameters. FO protected against excessive weight gain mainly under SD conditions.

CONCLUSIONS

The results show that FO confers more protection against cardiovascular risk factors (increased LDL and TG, decreased HDL) and liver lipid accumulation when given to rats consuming regular diets than when given to rats consuming a high-fat diet. This argues that priority should be given to consumption of a healthy diet rather than to the use of supplements. The effectiveness of n-3 PUFAs might be reduced in the case of hyperlipidic intake or after consumption of a high-fat diet.

Critical Differences Between Dietary Supplement and Prescription Omega-3 Fatty Acids: A Narrative Review

INTRODUCTION

Currently available omega-3 (OM-3) fatty acid products in the US are either nonprescription dietary supplements (e.g., fish oils) or prescription (Rx) medications. As such, we aimed to describe critical therapeutic differences among the OM-3 fatty acids, focusing on differences between fish oil supplements and Rx OM-3s.

METHODS

A narrative review of known papers salient to this topic was conducted.

RESULTS

Despite the multiple purported clinical benefits, the published evidence for OM-3 dietary supplements is generally insufficient, inconsistent, or negative. Rx OM-3 products are indicated as an adjunct to diet to reduce triglycerides (TG) in adults with severe hypertriglyceridemia (TG ≥ 500 mg/dl). Recently, the Rx eicosapentaenoic acid (EPA)-only OM-3, icosapent ethyl, demonstrated cardiovascular (CV) risk reduction among statin-treated patients at high risk of CV disease in a large CV outcomes trial (CVOT), and is now also indicated as an adjunct to maximally tolerated statin therapy to reduce the risk of myocardial infarction, stroke, coronary revascularization, and unstable angina requiring hospitalization in adult patients with elevated TG (≥ 150 mg/dL) and established CVD or diabetes mellitus and ≥ 2 additional risk factors for CVD. In contrast to the rigorous regulatory standards for safety, efficacy, and manufacturing of medications (whether Rx or over the counter), the Food and Drug Administration manages dietary supplements as food. Issues specific to OM-3 dietary supplements include variable content, labeling inconsistencies, and poor product quality/impurity. Given these issues, OM-3 dietary supplements should not be substituted for Rx OM-3 products. The efficacy of the EPA-only Rx OM-3 product in a large CVOT cannot be extrapolated to other OM-3 products.

CONCLUSION

Consumers and health care providers need to recognize critical differences between Rx and OM-3 dietary supplements to ensure appropriate use of each OM-3 product.