Fats & Fatty Acids
Trans Fat
Trans fatty acids (TFAs) are unsaturated fats with at least one double bond in the trans configuration — a geometric arrangement that makes them behave more like saturated fats in the body. There are two types: industrial trans fats, created by partial hydrogenation of vegetable oils (used in margarines, shortening, and processed foods), and naturally occurring ruminant trans fats (primarily vaccenic acid and conjugated linoleic acid, CLA) found in small amounts in dairy and beef. Industrial trans fats have no safe level of consumption — the FDA banned partially hydrogenated oils (PHOs) as Generally Recognised as Safe (GRAS) in 2015, with full compliance required by 2018. The WHO set a global target to eliminate industrial trans fats from the food supply by 2023. Despite regulatory progress, trans fats persist in some processed foods, imported products, and restaurant fried foods. See the foods that still contain trans fats from USDA data.
Top Source
Shortening, industrial, soy (partially hydrogenated ) for baking and confections
42.9 g
What Does Trans Fat Do?
- Ruminant trans fats (CLA, vaccenic acid) have distinct properties — conjugated linoleic acid (CLA) — found naturally in dairy and grass-fed beef — shows anti-obesity, anti-carcinogenic, and immune-modulating effects in animal studies. Vaccenic acid, the most abundant naturally occurring trans fat in dairy, is converted to CLA in the body. These naturally occurring TFAs are metabolically different from industrial PHO-derived trans fats and are not subject to the same health concerns.
- No known nutritional benefit for industrial trans fats — industrial trans fats provide no health benefit that could not be obtained from saturated or unsaturated fats. They were adopted by the food industry because they extend shelf life, improve texture, and are cheaper than alternatives — not for nutritional reasons.
Signs of Trans Fat Deficiency
Trans fat is not a nutrient — there is no deficiency syndrome, no RDA, and no AI. The only evidence-based dietary recommendation is to minimise industrial trans fat intake to as close to zero as practically possible. The FDA requires trans fat content to be listed on Nutrition Facts labels (as "Trans Fat"), and foods may claim "0g trans fat" if they contain less than 0.5g per serving — meaning products labelled 0g may still contain small amounts if portions are small.
- Trans fat is not an essential nutrient — there is no deficiency syndrome
- The relevant concern is excess intake, not deficiency
- Even small amounts of industrial trans fats (2% of daily energy) significantly increase cardiovascular risk
How to Get the Most from Trans Fat
Industrial trans fats are absorbed with the same efficiency as cis unsaturated fats (~95%), but they are metabolised differently. Their trans configuration makes them poor substrates for the desaturase and elongase enzymes that normally process unsaturated fats — instead they interfere with these pathways, displacing essential fatty acids and disrupting membrane function.
Check ingredient lists for "partially hydrogenated oils" — not just the Nutrition Facts label
In the US, foods can be labelled "0g trans fat" if a serving contains less than 0.5g. If a product lists "partially hydrogenated" oil in its ingredients, it contains industrial trans fat even if the label says 0g. The FDA ban on PHOs effectively applies to products manufactured after 2018, but products manufactured before the deadline could remain on shelves. Imported foods may not comply with US regulations.
High-temperature frying with vegetable oils generates some trans fats
When polyunsaturated vegetable oils are heated repeatedly to very high temperatures (especially above 200°C / 392°F in deep fryers), small amounts of trans fats can form through thermally induced geometric isomerisation. Using more heat-stable oils (olive oil, avocado oil, refined coconut oil) for high-heat cooking and avoiding repeatedly reheated oils minimises this minor but real source of trans fat.
Naturally occurring ruminant trans fats do not require avoidance
Dairy and beef contain small amounts (3–6% of fat) of naturally occurring trans fats — mainly vaccenic acid and CLA. Unlike industrial trans fats, these do not raise cardiovascular risk and may have modest health benefits (CLA shows anti-inflammatory properties in some studies). They do not require reduction based on current evidence.
Common Trans Fat Questions
Why are trans fats bad for you?
Industrial trans fats raise LDL ("bad") cholesterol and lower HDL ("good") cholesterol simultaneously — making them more cardiovascular-harmful per gram than any other dietary fat, including saturated fat. They also promote inflammation and endothelial dysfunction. Meta-analyses estimate that every 2% of calories from industrial trans fats increases coronary heart disease risk by approximately 23%. The WHO estimates trans fat causes approximately 500,000 cardiovascular deaths per year globally.
Are trans fats still in food?
In the US, the FDA formally banned partially hydrogenated oils (PHOs) — the primary source of industrial trans fats — from the food supply (full compliance by 2018). In other countries, regulations vary: some have banned or set limits; others have no regulations. Industrial trans fats persist in some imported foods, products made before the deadline that remain in circulation, and restaurant fried foods using repeatedly heated oils. Reading ingredient lists for "partially hydrogenated" oil is the most reliable check.
How much trans fat per day is safe?
There is no safe minimum intake for industrial trans fats — the WHO, AHA, and US dietary guidelines all recommend minimising intake to as low as possible. The European Food Safety Authority (EFSA) set a maximum guidance level of 1% of total energy (about 2g/day on a 2,000 kcal diet). Naturally occurring ruminant trans fats (in dairy and beef) are not covered by these recommendations and do not require reduction based on current evidence.
What foods are highest in trans fats?
Foods historically highest in industrial trans fats (pre-ban): stick margarine, commercial shortening, commercially fried fast food, packaged baked goods (crackers, cookies, pastries), and microwave popcorn made with PHOs. Post-ban US foods are substantially lower, but globally: some imported cookies/crackers, some fast food chains operating in countries without bans, and some fried street food cooked in repeatedly heated oils still contain significant amounts.
Is margarine high in trans fat?
Historically, yes — stick margarine was one of the highest trans fat foods. Modern margarines in the US and most high-income countries have been reformulated to use non-hydrogenated oils or interesterified fats and now contain negligible trans fat. Soft or liquid margarines labelled "no partially hydrogenated oils" are effectively trans-fat free. Check the ingredient list for "partially hydrogenated" to verify.