Edible Oils are in 3 forms on the basis of processing viz. Crude Oil, Refined Oil and Vanaspati. The uninitiated, based on the terms used, will perceive

• Crude oil is natural and not yet fit for consumption
• Refined oil is improved and made perfect for consumption
• Vanaspati, in Sanskrit means ‘lord of forest’, should be very healthy

This is where consumers are misguided by the names and their literal meanings. The fact though is

• Crude Oil that is just filtered after extracting oil from the oil seed is the healthiest. Unrefined oils still have healthy bioactive components, Vitamin E, flavour and aroma.
• Refined Oil is highly processed with the use of chemicals and heat to just retain the oil. Even oils extracted from lower quality oil seed can be refined. So, refined oil though pure is not as healthy as corresponding crude/unrefined oil.
• Vanaspati is formed by partial hydrogenation of refined vegetable oil is extremely harmful. They have Trans fats which are formed as a by product of hydrogenation.

In India, of the total 13 million tons of edible oil consumed, 10% is in the form of Vanaspati and 45% each in refined and unrefined form. Doctors and Health Departments warn consumers against intake of saturated fats, but the real culprit for all the heart problems and obesity are trans fats. Chemical analysis of trans fats gives a logical reason why trans-fats are harmful.

Chemistry of Fats
Fatty acids are characterized as either saturated or unsaturated based on the presence of double bonds in its structure. If the molecule contains no double bonds, it is said to be saturated; otherwise, it is unsaturated to some degree. A saturated fat has no double bonds, has the maximum number of hydrogens bonded to the carbons, and therefore is “saturated” with hydrogen atoms. The more double bonds in the fatty acid the more vulnerable it is to rancidity, as free radicals attack double bonds.

In most naturally occurring unsaturated fatty acids (and all saturated fatty acids), the hydrogen atoms are on the same side of the double bonds of the carbon chain (cis configuration — from the Latin, meaning “on the same side”). However, partial hydrogenation reconfigures most of the double bonds that do not become chemically saturated, twisting them so that the hydrogen atoms end up on different sides of the chain. This type of configuration is called trans, from the Latin, meaning “across.” The trans conformation is the lower energy form, and is favored when catalytically equilibriated as a side reaction in hydrogenation.

The trans configuration is straighter, while the cis configuration is noticeably kinked. Trans fats have a much higher melting point (45 °C), due to the ability of the trans molecules to pack more tightly, forming a solid that is more difficult to break apart. This notably means that it is a solid at human body temperatures (37 °C).

In essence, hydrogenated oil/trans fats are stable making the food products last longer and are solids at body temperature making it harder to digest.

Why Hydrogenate?
Hydrogenated oils are more stable than corresponding natural oils with unsaturated fats. Saturated fats are mostly found in animal sources (Butter, Ghee etc) which are scarce and hence expensive. Oils from vegetable sources are mostly unsaturated, abundant and less expensive. So, partial hydrogenation of less expensive unsaturated fats from vegetable sources is an attractive commercial proposition. They are not only stable and make the fried food product last longer but also adds to the taste. That is why we find widespread use in commercial cooking in Breads, Cookies, Cream Biscuits, Sweets, fried snacks, chocolates and ice creams.

Health Risks
The primary health risk identified for trans fat consumption is an elevated risk of coronary heart disease. The reason is trans fat increases the level of LDL or bad cholesterol and decreases HDL or good cholesterol. Other ill-effects are Alzheimer’s disease, Cancer, Diabetes, Obesity, Liver dysfunction and infertility in women.

Prevention of Food Adulteration Act specifies that the melting point of Vanaspati be strictly less than 41 °C. That means manufactures must ensure that hydrogenation is stopped before melting point reaches that point. Also, the labels in packed food products must show the amount of trans fats in the food sample. ITC, Britannia and the likes who are branded manufacturers of such food products clearly mention that Trans fats are bad for health just like Cigarette packs mention ‘Smoking is injurious to health’.

It is highly advised that consumers avoid all commercially prepared foods (Bakeries, Hotels and Packed foods) to the extent possible. One should also carefully read the labels for its ingredients and nutrition values. Food items containing Edible Vegetable Fat or having Trans fats value more than 2% should be avoided.

Sources – http://en.wikipedia.org/wiki/Trans_fat