What Type of Fat is Hydrogenated?

January 12, 2026 •

2 min read

Over 30,000 cardiac deaths per year in the United States were once estimated to be attributable to the consumption of trans fats. Hydrogenation is a chemical process that transforms liquid unsaturated fats, typically vegetable oils, into solid or semi-solid fats, fundamentally altering their molecular structure. The resulting product, or hydrogenated fat, can be either a harmful trans fat or an artificially saturated fat, depending on the process.

Quick Summary

Hydrogenated fats are created from unsaturated oils via a chemical process. The process can be partial, which creates harmful trans fats, or full, which creates an artificially saturated fat. This transformation is used to extend shelf life and alter texture in many processed foods. Due to associated health risks, partial hydrogenation and artificial trans fats have been banned or restricted in many regions.

Key Points

Trans Fats are a type of hydrogenated fat: Specifically, partially hydrogenated oils contain artificial trans fats, which are created during an incomplete chemical process.
Full vs. Partial Hydrogenation: Full hydrogenation creates artificially saturated fat and does not produce trans fat, while partial hydrogenation is the source of artificial trans fat.
Unsaturated to Saturated Transformation: Hydrogenation turns liquid unsaturated oils into solid or semi-solid fats by adding hydrogen atoms and breaking double bonds.
Health Risks of Trans Fats: Artificial trans fats raise 'bad' LDL cholesterol and lower 'good' HDL cholesterol, significantly increasing the risk of heart disease.
Reading Labels is Crucial: Consumers can find hydrogenated fats in processed foods like margarine, shortening, and baked goods, and should look for "hydrogenated oil" on ingredient lists.

Understanding the Hydrogenation Process

Hydrogenation is an industrial process where hydrogen is added to liquid unsaturated oils, like vegetable oil, with a metal catalyst. This converts unsaturated double bonds to single bonds, making the oil solid or semi-solid at room temperature and more stable. This stability extends shelf life and improves performance in cooking applications like frying.

There are two main types of hydrogenation: partial and full.

Partially Hydrogenated Fats: The Trans Fat Danger

Partial hydrogenation incompletely saturates the oil, creating artificial trans fats. These trans fats have an unnatural shape that is difficult for the body to process.

Health risks of trans fat include:

Increased "bad" LDL cholesterol and decreased "good" HDL cholesterol, raising the risk of heart disease.
Increased inflammation linked to heart disease, stroke, and diabetes.

Due to these risks, the FDA banned partially hydrogenated oils (PHOs) from manufactured foods in the US in 2015.

Fully Hydrogenated Fats: Artificially Saturated

Full hydrogenation saturates almost all double bonds, resulting in a completely saturated fat with no artificial trans fat. This solid fat is similar to natural saturated fats. While free of trans fats, it is still a saturated fat, and health guidelines recommend limiting saturated fat intake to reduce heart disease risk.

Comparison Table: Partially vs. Fully Hydrogenated Fat


Feature	Partially Hydrogenated Fat	Fully Hydrogenated Fat
Chemical Result	Creates artificial trans fats.	Creates artificially saturated fats.
Physical State	Semi-solid.	Solid.
Health Impact	Significant negative risks; affects cholesterol.	Less harmful than trans fats, but still a saturated fat.
Regulatory Status	Largely banned in the US.	Permitted by FDA, but intake should be limited.
Shelf Life	Extended.	Extended.

Where Hydrogenated Fats are Found Today

Even after the PHO ban, hydrogenated fats, primarily fully hydrogenated oils, are still used in some products:

Margarine and shortening: Reformulated to use fully hydrogenated oils.
Baked goods: Processed items may use hydrogenated fats for texture.
Fried foods: Used for heat tolerance.
Snack foods: Can contain hydrogenated ingredients.
Coffee creamers: May use hydrogenated oils.

Check ingredient lists for "hydrogenated vegetable oil" or "fully hydrogenated oil".

Conclusion: Navigating Hydrogenated Fats

Hydrogenated fat is an oil modified through an industrial process. Partial hydrogenation creates harmful artificial trans fat, which is largely banned due to severe heart health risks. Full hydrogenation results in an artificially saturated fat, which, while free of trans fats, should be consumed in moderation as part of a healthy diet. Reading ingredient labels helps consumers manage their intake of these fats.

An excellent resource for further reading on dietary fat is the Harvard T.H. Chan School of Public Health's page on types of fat. [https://nutritionsource.hsph.harvard.edu/what-should-you-eat/fats-and-cholesterol/types-of-fat/]

Frequently Asked Questions

The primary difference lies in the level of processing and the resulting chemical structure. Partially hydrogenated oils contain artificial trans fats due to incomplete saturation, while fully hydrogenated oils are completely saturated and contain no artificial trans fat.

Manufacturers used partially hydrogenated oils to extend the shelf life of products, enhance texture, and because they were a cheaper alternative to naturally solid animal fats. They also function well for frying because of their high stability.

No. While most trans fats consumed are artificially created through partial hydrogenation, small amounts of naturally occurring trans fats can be found in the meat and dairy products of ruminant animals like cows and sheep.

Artificial trans fats negatively impact cholesterol levels by raising low-density lipoprotein (LDL) or 'bad' cholesterol and lowering high-density lipoprotein (HDL) or 'good' cholesterol.

Fully hydrogenated oil is an artificially saturated fat and should be consumed in moderation, just like any other saturated fat. It does not carry the same specific heart risks as trans fats, but excessive saturated fat intake is still discouraged by health experts.

To identify hydrogenated fats, read the ingredient list on packaged foods. Look for terms such as "hydrogenated oil" or "fully hydrogenated oil." While "partially hydrogenated oil" is largely banned, some products may still contain trace amounts, so checking the label is essential.

The FDA revoked the 'Generally Recognized as Safe' (GRAS) status of partially hydrogenated oils in 2015 because of strong scientific evidence linking artificial trans fats to an increased risk of cardiovascular disease.