Journal of Nutraceuticals and Health

Omega-3 fatty acids

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Omega-3 fatty acids are essential fats that our bodies can't produce, so we need to obtain them through our diet. They are well-known for their anti-inflammatory properties and benefits for heart and brain health. Foods rich in omega-3s include fish like salmon and mackerel, as well as flaxseeds and walnuts. Consuming omega-3s daily can help lower the risk of heart disease, reduce inflammation, and improve cognitive function, contributing to overall well-being. These fats are also referred to as omega-3 oils, ω-3 fatty acids, or n-3 fatty acids. They play a vital role in human physiology and nutrition, are widely found in nature, and are key components of lipid metabolism in animals. The three main types of omega-3 fatty acids important for our health are α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found in plants, while DHA and EPA are primarily sourced from fish and algae. Omega-3 fatty acids are predominantly present in marine algae and phytoplankton.

In fish that eat this algae, DHA and EPA accumulate. Common plant sources of ALA include walnuts, edible seeds, flaxseeds, and hempseed oil, while fish, fish oils, and algal oil are typical sources of EPA and DHA.

Many animals cannot produce the necessary omega-3 fatty acid ALA on their own and must get it from their diet. But when ALA is available, they can use it to make EPA and DHA by lengthening its carbon chain (elongation) and adding more double bonds (desaturation). Specifically, EPA (20 carbons and 5 double bonds) is made from ALA (18 carbons and 3 double bonds), which is subsequently used to create DHA (22 carbons and 6 double bonds).

An omega-3 fatty acid is a type of fatty acid that contains multiple double bonds, with the first double bond located between the third and fourth carbon atoms from the end of the carbon chain. Omega-3 fatty acids are categorized as "long-chain" if they have 20 or more carbon atoms, while "short-chain" fatty acids have 18 or fewer carbon atoms.

Human physiology relies on three key omega-3 fatty acids: docosahexaenoic acid (22:6, n−3; DHA), eicosapentaenoic acid (20:5, n−3; EPA), and α-linolenic acid (18:3, n−3; ALA). The carbon chains of these three polyunsaturated fatty acids contain 18, 20, or 22 carbon atoms, respectively, with 3, 5, or 6 double bonds. All of these double bonds are in the cis-configuration, which means that the two hydrogen atoms are positioned on the same side of the double bond, similar to most naturally occurring fatty acids. Methylene bridges (-CH2-) separate the double bonds, creating two single bonds between each pair of adjacent double bonds.

The efficiency with which humans can convert short-chain omega-3 fatty acids into long-chain versions (EPA, DHA) is less than 5%. Although less research has been done, women have a higher omega-3 conversion efficiency than men. Women's plasma phospholipids may have higher levels of ALA and DHA because desaturases, particularly delta-6-desaturase, are more active in these tissues.