Omega-3 fatty acid

However, they can use ALA, when available, to form EPA and DHA, by creating additional double bonds along its carbon chain (desaturation) and extending it (elongation).

[8][9][10] Fish oil supplement studies have failed to support claims of preventing heart attacks or strokes or any vascular disease outcomes.

[14] Since then, researchers have shown a growing interest in unsaturated essential fatty acids as they form the framework for the organism's cell membranes.

[2][20] One way in which an unsaturated fatty acid is named is determined by the location, in its carbon chain, of the double bond which is closest to the methyl end of the molecule.

[clarification needed] The 'essential' fatty acids were given their name when researchers found that they are essential to normal growth in young children and animals.

[25] The eicosanoids typically have a short period of activity in the body, starting with synthesis from fatty acids and ending with metabolism by enzymes.

[32] A balanced intake ratio of 1:1 was believed to be ideal in order for proteins to be able to synthesize both pathways sufficiently, but this has been controversial as of recent research.

[2][34] Women have higher ALA-to-DHA conversion efficiency than men, which is presumed[35] to be due to the lower rate of use of dietary ALA for beta-oxidation.

Omega−6 and omega−3 eighteen-carbon polyunsaturated fatty acids compete for the same metabolic enzymes, thus the omega−6:omega−3 ratio of ingested fatty acids has significant influence on the ratio and rate of production of eicosanoids, a group of hormones intimately involved in the body's inflammatory and homeostatic processes, which include the prostaglandins, leukotrienes, and thromboxanes, among others.

[54] The Institute of Medicine has not established a RDA or AI for EPA, DHA or the combination, so there is no Daily Value (DVs are derived from RDAs), no labeling of foods or supplements as providing a DV percentage of these fatty acids per serving, and no labeling a food or supplement as an excellent source, or "High in..."[citation needed] As for safety, there was insufficient evidence as of 2005 to set an upper tolerable limit for omega−3 fatty acids,[54] although the FDA has advised that adults can safely consume up to a total of 3 grams per day of combined DHA and EPA, with no more than 2 g from dietary supplements.

[1] The European Commission sponsored a working group to develop recommendations on dietary fat intake in pregnancy and lactation.

The World Health Organization recommends regular fish consumption (1-2 servings per week, equivalent to 200 to 500 mg/day EPA + DHA) as protective against coronary heart disease and ischaemic stroke.

[61] Throughout their history, the Council for Responsible Nutrition and the World Health Organization have published acceptability standards regarding contaminants in fish oil.

[62][non-primary source needed] Fish oils that are molecularly distilled under vacuum typically make this highest-grade; levels of contaminants are stated in parts per billion per trillion.

[4][5] The microalgae Crypthecodinium cohnii and Schizochytrium are rich sources of DHA, but not EPA, and can be produced commercially in bioreactors for use as food additives.

[91] Some transgenic initiatives have transferred the ability to make EPA and DHA into existing high-yielding crop species of land plants:[92] Eggs produced by hens fed a diet of greens and insects contain higher levels of omega−3 fatty acids than those produced by chickens fed corn or soybeans.

[97] In addition to feeding chickens insects and greens, fish oils may be added to their diets to increase the omega−3 fatty acid concentrations in eggs.

[98] The addition of flax and canola seeds, both good sources of alpha-linolenic acid, to the diets of laying chickens, increases the omega−3 content of the eggs, predominantly DHA.

[100] The addition of green algae or seaweed to the diets boosts the content of DHA and EPA, which are the forms of omega−3 approved by the FDA for medical claims.

[104] The omega−3 content of chicken meat may be enhanced by increasing the animals' dietary intake of grains high in omega−3, such as flax, chia, and canola.

[108] A Canadian company, FeelGood Natural Health, pleaded guilty in 2023 to illegally selling seal oil capsules to American consumers.

[113] Moderate and high quality evidence from a 2020 review showed that EPA and DHA, such as that found in omega−3 polyunsaturated fatty acid supplements, does not appear to improve mortality or cardiovascular health.

[127] In people with chronic kidney disease (CKD) who require hemodialysis, vascular blockage due to clotting may prevent dialysis therapy.

A 2013 systematic review found tentative evidence of benefit for lowering inflammation levels in healthy adults and in people with one or more biomarkers of metabolic syndrome.

[129] Consumption of omega−3 fatty acids from marine sources lowers blood markers of inflammation such as C-reactive protein, interleukin 6, and TNF alpha.

[138] Another review concluded that the evidence is inconclusive for the use of omega−3 fatty acids in behavior and non-neurodegenerative neuropsychiatric disorders such as ADHD and depression.

[141] A 2021 umbrella review with moderate to high quality of evidence suggested that "omega-3 supplementation during pregnancy can exert favorable effects against pre-eclampsia, low-birth weight, pre-term delivery, and post-partum depression, and can improve anthropometric measures, immune system, and visual activity in infants and cardiometabolic risk factors in pregnant mothers.

[152][153] A significant correlation between shorter treatment trials was associated with increased omega−3 efficacy for treating depressed symptoms further implicating bias in publication.

[155][156] A 2020 review suggested that omega−3 supplementation has no effect on global cognitive function but has a mild benefit in improving memory in non-demented adults.

[157] A 2022 review found promising evidence for prevention of cognitive decline in people who regularly eat long-chain omega−3 rich foods.