There’s evidence that points to the mechanism behind the effects of fish oil on body composition, showing that fat burning at rest is increased with 6 grams/day of fish oil supplementation, and additional research suggests that higher omega-3 levels may be helpful for enhancing satiety during weight loss efforts. Other evidence suggests that fat loss may be a side-effect of the reduction in inflammation that fish oil can help with. Any way you look at it, supporting your dietary habits with 4 or more grams of fish oil per day is probably a good idea!

To avoid fish oil supplements containing mercury or other harmful contaminants, purchase supplements from a reputable source that clearly tests for these health-hazardous contaminants in its products. These tests should be ideally conducted by a third-party, and a certificate of analysis should indicate the levels of purity from environmental toxins.


There are three types of omega-3 fatty acids, which include EPA, DHA and ALA, which is alpha-linoleic acid. Although EPA and DHA are found to have high amounts from animal sources, ALA is found in rich concentrations in plant sources, including certain vegetable oils and flaxseeds, although fatty fish and shellfish are the best sources of EPA and DHA, according to the National Center for Complementary and Alternative Medicine. Examples of these fatty fish and shellfish include salmon, tuna, trout, crab, oysters and mussels.
AD is a devastating disease for which there are limited treatment options and no cure. Memory loss is an early indicator of the disease, which is progressive, and leads to the inability of the patient to care for him- or herself and eventually to death (47). Currently, the number of individuals with AD is estimated to be 26.6 million and is expected to increase to 106.2 million by 2050 (48). There have been many studies conducted regarding the use of omega-3 fatty acid supplementation and AD (Table 2). DHA is present in large amounts in neuron membrane phospholipids, where it is involved in proper function of the nervous system, which is why it is thought to play a role in AD (49). A case-control study consisting of 148 patients with cognitive impairment [Mini-Mental State Examination (MMSE) score <24] and 45 control patients (MMSE score ≥24) showed that serum cholesteryl ester-EPA and -DHA levels were significantly lower (P < 0.05 and P < 0.001, respectively) in all MMSE score quartiles of patients with AD compared with control values (49). Another study found that a diet characterized by higher intakes of foods high in omega-3 fatty acids (salad dressing, nuts, fish, tomatoes, poultry, cruciferous vegetables, fruits, dark and green leafy vegetables), and a lower intake of foods low in omega-3 fatty acids (high-fat dairy products, red meat, organ meat, butter) was strongly associated with a lower AD risk (50). Image analysis of brain sections of an aged AD mouse model showed that overall plaque burden was significantly reduced by 40.3% in mice with a diet enriched with DHA (P < 0.05) compared with placebo. The largest reductions (40–50%) were seen in brain regions that are thought to be involved with AD, the hippocampus and parietal cortex (51). A central event in AD is thought to be the activation of multiple inflammatory cells in the brain. Release of IL-1B, IL-6, and TNF α from microglia cells may lead to dysfunction of the neurons in the brain (52). In 1 study, AD patients treated with EPA+DHA supplementation increased their plasma concentrations of EPA and DHA, which were associated with reduced release of inflammatory factors IL-1B, IL-6, and granulocyte colony–stimulating factor from peripheral blood mononuclear cells (53).

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Weak bones (osteoporosis). Research suggests that taking fish oil alone or together with calcium and evening primrose oil slows the rate of bone loss and increases bone density at the thigh bone (femur) and spine in elderly people with osteoporosis. But taking fish oil does not slow bone loss in older people with osteoarthritis in the knee but without weak bones.
Hamazaki, K., Itomura, M., Huan, M., Nishizawa, H., Sawazaki, S., Tanouchi, M., Watanabe, S., Hamazaki, T., Terasawa, K., and Yazawa, K. Effect of omega-3 fatty acid-containing phospholipids on blood catecholamine concentrations in healthy volunteers: a randomized, placebo-controlled, double-blind trial. Nutrition 2005;21(6):705-710. View abstract.
The way that fish oil does that is to interfere with carbohydrate metabolism, and in insulin-resistant people or in people with specific genetic differences that might predispose them to having very high triglycerides, you do benefit from interfering that pathway with the fish oil, but I would actually try a low-carbohydrate diet in a lot of those situations to see if that helps with lowering triglycerides, or in the case of insulin resistance, I would try to address the insulin resistance at its root cause.
In addition, there was no significant difference in the association of treatment with reduced anxiety symptoms between participants receiving omega-3 PUFAs and those not receiving omega-3 PUFAs in the adolescent subgroup (aged <18 years) (k, 3; Hedges g, 0.020; 95% CI, –0.209 to 0.250; P = .86),48,53,57 in the adult subgroup (aged ≥18 years but <60 years) (k, 11; Hedges g, 0.388; 95% CI, –0.012 to 0.788; P = .06),33,35,36,47,49-51,54-56,59 or in the elderly subgroup (aged ≥60 years) (k, 3; Hedges g, –0.112; 95% CI, –0.406 to 0.181; P = .45).52,58,60 These insignificant results might be due to the smaller sample sizes in each subgroup.
A lot of the benefit of fish oil seems to come from the omega-3 fatty acids that it contains. Interestingly, the body does not produce its own omega-3 fatty acids. Nor can the body make omega-3 fatty acids from omega-6 fatty acids, which are common in the Western diet. A lot of research has been done on EPA and DHA, two types of omega-3 acids that are often included in fish oil supplements.
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