Trans fats are formed when hydrogen atoms are incorporated into poly-unsaturated vegetable oils. To improve the physical characteristics of liquid oils, manufacturers add hydrogen into these potential unsaturated spaces and convert them into solid fats.
Why should you bother about trans fats?
During the hydrogenation process these light vegetable oils get converted into solid saturated fats. Additionally, a kind of chemical reaction occurs resulting in a configuration change (ie) from its natural cis-form to trans-form.
Traditionally, cooking oils are either poly-unsaturated (Sunflower oil) or mono-unsaturated (Olive oil) oils. When oils get converted to trans fats, they behave much like saturated fats inside the body, that is, they elevate "bad cholesterol" or LDL levels and decrease the "good cholesterol" or HDL levels in the blood.
Trans fats are not present naturally in plants and occur only in small amounts in meat and dairy products as vaccenic acid. Actually, most trans fats consumed today are created industrially through partial hydrogenation of vegetable oils. The so formed saturated fats have higher melting points and longer shelf-life which makes them attractive for frying and baking. However, high temperature boiling also catalyzes a side- reaction that isomerizes some of the cis-unsaturated fats into trans-unsaturated fats instead of hydrogenating them completely. Trans fats formed from partially hydrogenated oils are, in fact, more dangerous to health than naturally occurring saturated fats like coconut oil, palm oil etc.
Furthermore, deep frying of food items (especially those rich in starch like corn-flour) results in the production of toxic chemical "acrylamide," deep brown color soot like compound that develops on the surface of fried items. Eating excess of acrylamide for prolonged periods might cause liver cell and colon cancers.
So what is the permissible level of Trans fats ?
Nil.In fact, there are no safe levels for trans-fats in the diet and unlike other dietary fats, trans fats are not at all essential for our body. New England Journal of Medicine (NEJM-2006 edition) scientific review states "from a nutritional standpoint, the consumption of trans fatty acids results in considerable potential harm but no apparent benefit.
Health risks of Trans fats
Coronary heart disease
Since trans-fats behave like saturated fats, they pose greater health risk of coronary heart disease (CHD), stroke and increased mortality.
Regular consumption of Trans fatty acids in the diet increases the risk of breast and prostate cancers.
Obesity and Diabetes
Trans fats may increase the weight gain(obesity) by favoring abdominal fat deposition. Obesity in turn is one of the major risk factor for type-2 diabetes.
A study published in Archives of Neurology in February 2003 suggested that the intake of both Trans fats and saturated fats leads to the development of Alzheimer disease.
Steps to avoid or to reduce Trans fat consumption in the diet
- Avoid hydrogenated fats like 'dalda' in foods.
- Avoid or minimize food preparations that use margarine, and shortenings such as cookies, pastry, etc.
- Use only small quantity of oil. See that the oil is not too high in temperature before food is put in.
- Do not re-use cooked oil.
- Use more stable oils at room temperature such as olive oil as add-on to foods, for instance, in salad dressing.
- Sauteing - using tomato and onions as a base, can substantially reduce the oil requirements
- Shallow or stir-frying - While frying, start with a small amount of oil at low heat and add small amounts of fresh oil to replace oil used up in frying.