Omega-3

Omega-3 fatty acids are essential fats the body can't make on its own. ALA comes mainly from plant sources like flaxseed and walnuts, while EPA and DHA — generally considered the most bioactive forms — come mainly from fatty fish.

What is it?

There are three main omega-3 fatty acids. ALA (alpha-linolenic acid) is found in plant oils and seeds; EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are found in fish, shellfish and algae, which are the original source of the fish's omega-3. The body can convert some ALA to EPA and DHA, but only in small amounts.

What it does

1. DHA is a major structural fat in the brain, retina and nerve cells
2. EPA and DHA lower blood triglycerides
3. Help regulate inflammation and blood clotting
4. Support fetal and infant brain and eye development

Food sources

EPA and DHA: salmon, mackerel, herring, sardines, anchovies (ikan bilis), trout, and to a lesser extent tuna, seabass and other fish and shellfish. ALA: flaxseed, chia seeds, walnuts, canola and soybean oil, and tofu. The table at the end of this page lists amounts per serving.

Singapore food examples

1. Salmon, mackerel, sardines, pomfret and seabass
2. Ikan bilis and other small whole fish
3. Canned sardines and mackerel
4. Walnuts, chia seeds and flaxseed
5. Canola oil and soya products such as tofu
6. Algae-based omega-3 supplements for vegetarians and vegans

How much do I need?

Singapore's RDA table does not list omega-3. The US National Academies' Adequate Intake for ALA is 1.6 g a day for men and 1.1 g for women (1.4 g in pregnancy and 1.3 g when breastfeeding). There is no official intake for EPA and DHA, but many health organisations suggest two servings of fish a week, including oily fish. See Singapore's age- and sex-specific Recommended Dietary Allowances (HealthHub) for the nutrients Singapore does list.

Low intake and deficiency

True deficiency is rare and causes dry, scaly skin, a rash and, in severe cases, nerve and vision problems. More commonly, people simply eat less omega-3 than is ideal, especially if they rarely eat fish. Low intake in pregnancy may affect a baby's brain and eye development.

Too much and safety

Omega-3 from food is safe. High-dose supplements (more than about 3 g of EPA and DHA a day) can increase bleeding risk, and trials at 1 g or more a day have linked fish-oil supplements to a higher risk of atrial fibrillation (an irregular heartbeat) in some people. They can also cause a fishy aftertaste, burping and loose stools. Talk to your doctor before taking supplements if you take blood thinners or have a heart condition.

Large predatory fish such as shark, swordfish, king mackerel and some tuna can contain high mercury. Pregnant and breastfeeding women and children should choose lower-mercury oily fish such as salmon, sardines and mackerel (Atlantic or Spanish in moderation) and follow local guidance.

Absorption and bioavailability

Omega-3 is absorbed best with a meal containing other fat. EPA and DHA in fish and in the triglyceride form of supplements are absorbed better than in ethyl ester forms. Conversion of ALA to EPA is low (under about 10 percent) and to DHA lower still (often under 1 percent), so plant omega-3 does not fully replace fish. Gentle cooking — steaming, baking, grilling — keeps more omega-3 than deep frying.

Connection to daily life

1. Heart health: lowers triglycerides and supports healthy heart rhythm
2. Brain, mood and eye health: DHA is a main structural fat in both
3. Pregnancy and infancy: important for a baby's brain and visual development
4. Healthy ageing: fish-rich eating patterns are linked with better heart and brain health
5. Exercise: regular fish intake supports recovery and joint health — see Exercise

Food sources table

Amounts per serving from NIH data, ranked from highest to lowest.

Sources: 1. NIH Office of Dietary Supplements — Omega-3 Fatty Acids Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/ 2. National Academies of Sciences, Engineering, and Medicine — Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005) 3. HealthHub Singapore — Recommended Dietary Allowances: https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/recommended_dietary_allowances 4. Health Promotion Board — Singapore Food Insights Database (SG FoodID): https://www.hpb.gov.sg/healthy-living/food-and-beverage/sgfoodid/ 5. FAO/INFOODS — Food composition tables and databases: https://www.fao.org/food-composition/tables-and-databases/en/ 6. NIH Office of Dietary Supplements — all fact sheets: https://ods.od.nih.gov/factsheets/list-all/ Food sources table: National Institutes of Health, Office of Dietary Supplements — Omega-3 Fatty Acids Fact Sheet for Health Professionals, Table 2.