Omega-3 fatty acids from fish and other sources are fats with a uniquely diverse range of health applications. Boosting intake of these healthy fats—particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—through diet and supplementation can support the body in multiple ways.
For instance: aging results in lower neural concentrations of omega-3 fatty acids, leading to neuronal loss and a decline in cognitive function; however, recent studies show that omega-3 fats can enhance neuron signaling and synaptic plasticity, while preserving gray and white matter in the brain.1 Another example: inflammation is increasingly linked to chronic disease, but research shows that omega-3 fats play important roles in reducing inflammation by lowering the concentration of pro-inflammatory eicosanoids such as thromboxane B2 and leukotriene B4.2 And yet another example: studies show that omega-3 fatty acids may benefit arterial structure by reducing arterial stiffness and improving endothelial function, while simultaneously reducing oxidative stress and inflammation and favorably modifying the expression of enzymes involved in the process of atherosclerosis.3
The ability of omega-3 fatty acids to influence so many processes in the human body is what makes omega-3 research so exciting. Ahead, we highlight some of the most recently published human studies showing beneficial effects of supplementation with omega-3 fatty acids on several health conditions.
Reducing Heart Risk: Omega-3s Plus Vitamin B12
Given the role omega-3 fats play in heart health and vascular health, Tao Huang and colleagues from Zheijang University in China recently studied the effects of fish oil EPA and DHA on several risk factors of heart disease in healthy young adults.4 The researchers also had another objective: to evaluate possible synergistic effects of the omega-3 fatty acids and vitamin B12, a vitamin known to lower homocysteine levels (a risk factor for heart health).
In the eight-week randomized controlled trial, 30 subjects with a mean age of 23 were divided into three groups. One group supplemented with vitamin B12 (1,000 mcg/day). The second group supplemented with 2 g of fish oil daily (containing 490 mg DHA and 98 mg of EPA per gram). The third group was given a combination of both the fish oil and vitamin B12 supplements.
The researchers conducted blood tests to monitor the impact of supplementation on levels of plasma homocysteine, ferritin (a measure of iron status), triglycerides, uric acid, and C-reactive protein (a measure of inflammation). Measurements taken during the study at four and eight weeks showed that all groups experienced significant decreases in all measures. Plasma homocysteine concentration declined from baseline by 22% in the vitamin B12 group, by 19% in the fish oil group, and by 39% in the combination-supplement group. While each nutrient individually was able to significantly lower markers of heart risk, the fish oil and vitamin B12 combination had a substantial synergistic impact, indicating a powerful benefit for heart and vascular health.
Eye Health: Protecting Retinal Function
X-linked retinitis pigmentosa is a genetic condition affecting the retina of the eye that leads to progressive vision loss in boys and young men. In those with the condition, night blindness occurs initially with progressive constriction of the visual field, leading to blindness at an average age of 45. Where do omega-3 fatty acids come in? Science indicates that individuals with this condition have a reduced ability to synthesize the omega-3 fatty acid DHA from other fatty acids.5 For this reason, researchers believe that oral supplementation with DHA may help bypass this defect and potentially slow the progression of the disease.
In an earlier, 2014-published trial—the DHAX (DHA in X-linked Retinitis Pigmentosa) trial—researchers found no effect from DHA supplementation on slowing the loss of cone or rod function in males with retinitis pigmentosa6. Recently, however, those same researchers published a paper analyzing ancillary outcomes of the original trial. Specifically, they looked at the effects of DHA supplementation in those participants who completely adhered to the treatment protocol.7
This ancillary analysis included 49 males who were 7 to 31 years old. Of those subjects, 29 had received DHA (30 mg/kg body weight daily in the triglyceride form), while 22 received a placebo, for four years. Visual parameters were measured yearly, while DHA concentrations were assessed every six months.
The researchers found that red blood cell levels of DHA increased fourfold over placebo in those supplementing with DHA. While visual parameters like visual acuity, ability to discriminate shapes, or the appearance of the fundus of the eye were not significantly different between groups, the researchers did detect statistically significant benefits in favor of DHA supplementation for reducing the progression of dark adapted thresholds, a measure of night vision. Furthermore, DHA supplementation also helped to attenuate the decline in visual field sensitivity over the four-year period. This sensitivity was determined to be linked to red blood cell levels of DHA—that is, higher concentrations of DHA led to less of a decline.
These findings indicate that DHA supplementation can benefit certain parameters of retinal health and visual function in individuals with retinitis pigmentosa.
The researchers further advocated for additional studies using higher doses of DHA in order to try to induce greater benefits. Based on the DHA dose of 30 mg/kg body weight administered in the study, red blood cell DHA concentrations averaged 10.9%. By extrapolating the results comparing the mean red blood cell levels of DHA and loss of visual field sensitivity, the authors postulated that a red blood cell DHA concentration of 17% could fully attenuate the loss of visual field sensitivity. An estimated DHA dose to attain this level of red blood cell saturation would be 45 mg/kg body weight per day.7
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- Cutuli D, “Functional and structural benefits induced by omega-3 polyunsaturated fatty acids during aging,” Current Neuropharmacology. Published online June 13, 2016.
- Jiang J et al., “Effect of marine-derived n-3 polyunsaturated fatty acids on major eicosanoids: a systematic review and meta-analysis from 18 randomized controlled trials,” PloS One. Published online January 25, 2016.
- Zanetti M et al., “Omega-3 polyunsaturated fatty acids: structural and functional effects on the vascular wall,” BioMed Research International. Published online August 2, 2015.
- Huang T et al., “Effect of vitamin B-12 and n-3 polyunsaturated fatty acids on plasma homocysteine, ferritin, C-reaction protein, and other cardiovascular risk factors: a randomized controlled trial,” Asia Pacific Journal of Clinical Nutrition, vol. 24, no. 3 (2015): 403–411
- Hoffman DR et al., “Impaired synthesis of DHA in patients with X-linked retinitis pigmentosa,” Journal of Lipid Research, vol. 42, no. 9 (September 2001): 1395–1401
- Hoffman DR et al., “Four-year placebo-controlled trial of docosahexaenoic acid in X-linked retinitis pigmentosa (DHAX trial): a randomized clinical trial,” JAMA Ophthalmology, vol. 132, no. 7 (July 2014): 866–873
- Hoffman DR et al., “ Docosahexaenoic acid slows visual field progression in X-linked retinitis pigmentosa: ancillary outcomes of the DHAX trial,” Investigative Ophthalmology and Visual Science, vol. 56, no. 11 (October 2015): 6646–6653
- Haghiac M et al., “Dietary omega-3 fatty acid supplementation reduces inflammation in obese pregnant women: a randomized double-blind controlled clinical trial,” PloS One. Published online September 4, 2015.
- Carlson SE et al., “DHA supplementation and pregnancy outcomes,” American Journal of Clinical Nutrition, vol. 97, no. 4 (April 2013): 808–815
- Grosso G et al., “Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials,” PloS One. Published online May 7, 2014.
- Duffy SL et al., “The effect of 12-wk Ω-3 fatty acid supplementation on in vivo thalamus glutathione concentration in patients ‘at risk’ for major depression,” Nutrition, vol. 31, no. 10 (October 2015): 1247–1254
- Anderson EL et al., “The prevalence of non-alcoholic fatty liver disease in children and adolescents: a systematic review and meta-analysis.” PloS One. Published online October 29, 2015.
- Boyraz M et al., “Long-term treatment with n-3 polyunsaturated fatty acids as a monotherapy in children with nonalcoholic fatty liver disease,” Journal of Clinical Research in Pediatric Endocrinology, vol. 7, no. 2 (June 2015): 121–127