The 0.5-Gram Loophole Still Exists
In 2015, the FDA ruled that partially hydrogenated oils (PHOs) — the primary source of artificial trans fats — were no longer Generally Recognized as Safe (GRAS). A compliance deadline of June 2018 effectively banned most uses of PHOs in US food manufacturing. Yet here is the critical loophole: products containing less than 0.5 grams of trans fat per serving can be labeled "0g Trans Fat." A product with 0.4g trans fat per serving eaten three times a day contributes 1.2g of trans fat daily — a meaningful amount given that the WHO recommends keeping trans fat intake below 1% of total calories (~2.2g for a 2,000-calorie diet).
What Are Trans Fats?
Trans fats come in two forms:
- Artificial trans fats (industrial): Created when hydrogen is added to liquid vegetable oils under pressure and with a catalyst (partial hydrogenation), making the oil solid at room temperature. This is the form that was effectively banned by the FDA.
- Natural trans fats (conjugated linoleic acid / CLA): Found naturally in small amounts in the fat from ruminant animals (beef, lamb, dairy). CLA and vaccenic acid (ruminant trans fats) appear to have neutral or modestly beneficial health effects — very different from industrial trans fats.
Why Industrial Trans Fats Are Uniquely Dangerous
Industrial trans fats have a uniquely damaging lipid profile effect: they simultaneously raise LDL cholesterol (the "bad" cholesterol) and lower HDL cholesterol (the "good" cholesterol). No other dietary fat does both. A 2% increase in trans fat intake is associated with a 23% increase in cardiovascular disease risk — the strongest diet-disease relationship for a single nutrient identified in nutrition epidemiology.
Trans fats also promote systemic inflammation, impair endothelial function (the lining of blood vessels), and may contribute to insulin resistance. The American Heart Association estimates that eliminating trans fats from the US food supply could prevent 10,000–20,000 heart attacks and 5,000–7,000 deaths annually.
How to Find Hidden Trans Fats
Even with near-elimination from the US food supply, trans fats can still appear in:
- Some shortenings and margarines: Check for "partially hydrogenated" in the ingredient list
- Older shelf-stable baked goods: Crackers, cookies, pie crusts, and pastries with long shelf lives sometimes still use PHOs
- Some microwave popcorn: Though most brands have reformulated
- Restaurant fryer oils: Restaurants are not subject to the same labeling requirements as packaged foods; some fast food chains and independent restaurants still use partially hydrogenated oils
- International and imported foods: PHO bans vary by country; imported snack foods may still contain artificial trans fats
The detection rule: Look for "partially hydrogenated" anywhere in the ingredient list. If it appears, the product contains trans fat regardless of what the Nutrition Facts panel says.
The Reformulation Landscape
When food manufacturers removed PHOs, they replaced them with several alternatives, each with different health profiles:
| PHO Replacement | Health Profile | Common Use |
|---|---|---|
| Palm oil / palm kernel oil | High in saturated fat; raises LDL but less harmful than trans fat | Crackers, cookies, margarine |
| Fully hydrogenated oils (FHO) | Contain stearic acid, which appears neutral for LDL; no trans isomers | Shortening, baked goods |
| Interesterified fats | Emerging; some animal research suggests metabolic concerns, human evidence limited | Margarine, spreads |
| High-oleic sunflower/canola oil | High in monounsaturated fat; favorable cardiovascular profile | Snacks, frying |
Interesterified Oils: The New Concern
Interesterified oils — created by rearranging the fatty acid structure of fully hydrogenated oils — are increasingly replacing PHOs. They have no trans fats, but early research raises questions. A 2007 study in Nutrition & Metabolism found that interesterified fat consumption raised fasting blood glucose and lowered HDL cholesterol in a small human trial. The evidence remains limited but warrants attention as these fats become more prevalent.
The Bottom Line
Scan the ingredient list for "partially hydrogenated" on every packaged food purchase. If it's present, the product contains artificial trans fat. For fats more broadly, check our trans fat ingredient guide and compare fat profiles between products using the ingredient comparison tool. The reformulated landscape is generally safer than the PHO era — but the shift to palm oil and interesterified fats introduces its own set of considerations worth understanding.