Do you know what happens when your favorite cooking oil set to boil at higher temperature? The answer is simple; it converts in to trans fats (trans fatty acids).
Now, what are these Trans-fats?
How do they form?
Why all of us are so concerned about trans-fats?
When the oil is set to boil at higher temperatures, a kind of chemical reaction occurs resulting in change in the configuration
of the oil from its natural cis-form to trans-form.
Traditionally, cooking oils are either poly unsaturated (eg. Sunflower oil) or mono-unsaturated (eg. Olive) oils. When oils deep boiled and converted to trans-fats, they behave like saturated fats in the body; that is, they elevate "bad cholesterol" or LDL levels and decrease the "good cholesterol" or HDL levels in the blood.
Trans fats do not present in the plants and only occur 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. Hydrogenation (addition of hydrogen atoms to cis-unsaturated fats) makes them more saturated. So formed saturated fats have higher melting points and have longer shelf-life which makes them attractive for frying and baking. However, deep boiling also catalyses 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 oils.
In addition, deep frying of food items (carbohydrate-rich) results in the production of toxic chemical "acrylamide"; a deep brown color, soot like substance on the outer surface of fried items. Excess of acrylamide might cause liver cell and colon cancers.
How much Trans fat is acceptable in the diet?
Nil.... In fact, there is 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 that states that "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, pose greater health risk of coronary heart disease (CHD), stroke and increased mortality.
Cancers: Regular consumption of Trans fatty acids in the diet increases the risk of breast and prostate cancers.
Obesity and Diabetes: Trans-fat may increase weight gain by favoring abdominal fat deposition. Obesity in turn is one of the major risk factor for type-2 diabetes.
Alzheimer's disease: A study published in Archives of Neurology in February 2003 suggested that the intake of both Trans-fats and saturated fats promote the development of Alzheimer disease.
Steps to avoid or at least to reduce Trans fat consumption in the diet.
- Avoid hydrogenated fats like "dalda" in foods.
- 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 eg. To salad dressing.
- Sautéing, use of tomato and onions as a base can substantially reduce the oil requirements.
- Shallow or stir frying.
- While frying, start with small amount of oil at low heat and add small amounts of fresh oil to replace oil used up in frying.
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