Edible oils come in three forms based on processing: Crude Oil, Refined Oil, and Vanaspati. The uninitiated, based on the literal meanings of these terms, might perceive:

• Crude oil as natural but not yet fit for consumption
• Refined oil as improved and made perfect for consumption
• Vanaspati, meaning ‘lord of the forest’ in Sanskrit, as something very healthy

This is where consumers are misled by the terminology. The reality, however, is quite different:

• Crude Oil: This is oil that is merely filtered after extraction from the oilseed. It is the healthiest form, as it retains healthy bioactive components such as Vitamin E, natural flavour, and aroma.
• Refined Oil: Highly processed using chemicals and heat to retain only the oil. Even oil extracted from lower quality seeds can be refined. Though refined oil is pure, it is not as healthy as its crude/unrefined counterpart.
• Vanaspati: Formed by partial hydrogenation of refined vegetable oil, Vanaspati contains trans fats, which are extremely harmful and are a by-product of hydrogenation.

In India, of the total 13 million tons of edible oil consumed annually, approximately 10% is Vanaspati, and 45% each is refined and unrefined oil. While doctors and health authorities warn against saturated fats, the real culprits for heart disease and obesity are trans fats. The chemistry of trans fats explains why they are so harmful.

Chemistry of Fats

Fatty acids are classified as saturated or unsaturated based on the presence of double bonds in their molecular structure. Saturated fats contain no double bonds and are fully "saturated" with hydrogen atoms. Unsaturated fats, containing one or more double bonds, are more vulnerable to rancidity due to free radical attacks on those bonds.

In naturally occurring unsaturated fats (and all saturated fats), hydrogen atoms are on the same side of the double bonds (cis configuration). Partial hydrogenation alters the remaining double bonds, twisting them so that hydrogen atoms are on opposite sides of the carbon chain — the trans configuration. This trans form is more stable and has a lower energy state, which is favored during hydrogenation.

The trans configuration results in a straighter molecular shape compared to the kinked cis configuration. Trans fats have a significantly higher melting point (about 45°C) because their molecules pack tightly, forming a solid at body temperature (37°C).

In essence, hydrogenated/trans fats are chemically stable, increase shelf life, and stay solid in the human body — making them harder to digest.

Why Hydrogenate?

Hydrogenated oils are more stable than their natural unsaturated counterparts. Saturated fats are mostly found in animal products like butter and ghee, which are costlier and less abundant. Vegetable oils are more plentiful and affordable but are typically unsaturated. Hence, partially hydrogenating inexpensive vegetable oils creates a cost-effective, shelf-stable fat with desirable cooking properties and taste. This is why hydrogenated fats are widely used in breads, cookies, cream biscuits, sweets, fried snacks, chocolates, and ice creams.

Health Risks

The primary health risk of trans fat consumption is an increased risk of coronary heart disease. Trans fats raise LDL (bad cholesterol) levels and lower HDL (good cholesterol). Other associated health risks include Alzheimer’s disease, cancer, diabetes, obesity, liver dysfunction, and infertility in women.

The Prevention of Food Adulteration Act mandates that Vanaspati must have a melting point below 41°C. Manufacturers must halt hydrogenation before reaching this point. Additionally, food labels must display trans fat content. Brands like ITC and Britannia clearly label their products, warning that trans fats are harmful — much like cigarette packs warning about smoking.

Consumers are strongly advised to avoid commercially prepared foods from bakeries, hotels, and packaged goods as much as possible. Always read labels for ingredients and nutritional values. Avoid products containing “Edible Vegetable Fat” or more than 2% trans fats.

Source: http://en.wikipedia.org/wiki/Trans_fat