Trans fats

Trans fats are unsaturated fats with a particular chemical shape that raises LDL ("bad") cholesterol and lowers HDL ("good") cholesterol. Artificial trans fats, made by partially hydrogenating vegetable oil, have no health benefit, and Singapore banned them from the food supply in 2021.

What is it?

There are two kinds. Artificial (industrial) trans fats are made when liquid oil is partially hydrogenated to make it firmer; they were once common in margarine, shortening, pastries, biscuits and fried foods. Natural trans fats occur in small amounts in the meat and milk of cows, sheep and goats.

What it does

1. Trans fats have no known nutritional benefit and no need in the diet
2. They were used by food manufacturers for texture, shelf life and frying

Food sources

Foods made with partially hydrogenated oil — some imported margarine, shortening, microwave popcorn, pastries, biscuits, crackers, fried fast food and baked goods — and small natural amounts in beef, lamb, butter and full-fat dairy. Check labels on imported products.

Singapore food examples

1. Singapore has banned partially hydrogenated oils from all food since 1 June 2021
2. Small amounts remain naturally in beef, mutton, butter and full-fat dairy
3. Imported or home-brought products may still contain trans fat — check the label for "partially hydrogenated oil"
4. Reheated or repeatedly used frying oil may also form small amounts of trans fats

How much do I need?

No safe level of artificial trans fat has been set. The World Health Organization recommends that trans fat provide less than 1 percent of daily energy. Singapore's dietary guidelines advise limiting trans fat as part of its fat advice — see Singapore's dietary guidelines for adults (HealthHub).

Low intake and deficiency

There is no deficiency — the body does not need trans fat.

Too much and safety

Trans fat raises LDL cholesterol, lowers HDL cholesterol and increases inflammation, raising the risk of heart disease, stroke and type 2 diabetes. For each 2 percent of energy from trans fat, the heart disease risk rises noticeably — one reason it was banned.

A product can say "trans fat 0 g" if a serving has less than 0.5 g in some countries; check the ingredient list for "partially hydrogenated" oils.

Absorption and bioavailability

Trans fats are absorbed like other fats, and incorporated into cell membranes and lipoproteins, where they interfere with normal function. They stay in the body for a long time.

Connection to daily life

1. Heart health: avoiding artificial trans fat is a simple way to protect the heart
2. Eating out and travelling: check labels on imported goods
3. Cooking: avoid repeatedly reusing frying oil

Sources: 1. National Academies of Sciences, Engineering, and Medicine — Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005) 2. HealthHub Singapore — Recommended Dietary Allowances: https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/recommended_dietary_allowances 3. HealthHub Singapore — Dietary guidelines for adults: https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/dietary_guidelines_adults 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/