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16 Sep 2008 09:18
As the global epidemic of obesity and related conditions such as heart disease and diabetes continues to grow, health professionals—and politicians—have started to target plant-based fats commonly used in the fast food industry and baked goods in an attempt to improve health.
Trans fatty acids (trans fats) are created by the partial hydrogenation of vegetable oils.
This involves adding hydrogen atoms to unsaturated fats, which contain double bonds between some of their carbon atoms.
Doing so makes a plant oil more solid, for example, making margarine easier to spread. The process makes vegetable oils more stable at high temperature and increases the “fry-life” of oil, so the oil can be re-used more often. It also gives baked products a longer shelf life.
Trans fats are found in vegetable shortenings, some margarines, foods fried or made with partially hydrogenated oils and many cookies and biscuits. A small amount of trans fat is found naturally in some animal-based foods.
Partially hydrogenated oils came into widespread use when the food industry shifted from “harmful” saturated fats to more beneficial unsaturated fats. To prevent the unsaturated fats from become rancid, the oils were “hydrogenated” to make them more stable.
While trans fat—like saturated fat and cholesterol—raises the levels of LDL (“bad”) cholesterol, which increases your risk of heart disease, trans fat goes one step further and actually decreases the levels of HDL (“good”) cholesterol in your body. New studies published this year have linked high blood levels of trans fats with an increased risk of breast cancer in women and prostate cancer in men.
Research published last week in the American Journal of Epidemiology also links high trans fat intake with an increased risk of colon cancer.
Because scientists don’t know what an appropriate level of trans fat is—other than that it should be low—there are no set daily values or uniform guidelines when it comes to trans fat consumption.
The American Heart Association recommends a daily intake of not more than 2g of trans fat; other health bodies argue there is no safe daily limit.
A typical fast food combo meal contains anything from 3g to 15g of trans fat, although major fast food chains are redeveloping their menus and cooking methods to become trans fat free.
In a bid to educate consumers a number of countries have recently passed legislation compelling food manufacturers to label the amount of trans fat found in each serving—although this can be misleading as in many instances foods with less than 0,5g of trans fat per 100g can be labelled as trans-fat free.
In July this year California became the first American state to pass a regional ban on the use of trans fats in restaurants (the ban comes into effect from 2010).
Several US cities, including New York, Seattle and Philadelphia, have imposed similar municipal restrictions.
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