   |  | | A quick history of trans fats | By Mike Magee, MD
A balanced diet is about taking in the recommended portions of protein, carbohydrates and fats. The American Heart Association recommends that fats should make up 30% or less of our daily diet.1,2 The right combination of fats is critical to life. Fats are an important source of energy, they’re essential for growth and development, and they help regulate blood pressure, heart rate, blood clotting, nerve transmissions and temperature control.
So why have fats, or more accurately, some fats, gotten a bad rap? The answer involves cholesterol, the waxy substance that’s critical to the production of some hormones and vitamin D. It’s important to limit the amount of cholesterol we eat, but cholesterol in the bloodstream is what’s really important. High blood cholesterol levels increase the risk for heart disease. The biggest influence on blood cholesterol? The mix of fats in the diet.3
The liver makes cholesterol. Once it’s on its way out of the liver and into the bloodstream, cholesterol is transported by a small molecule that is part fat and part protein – the low-density lipoprotein called LDL. When there is too much LDL cholesterol in the blood, it can be deposited on the walls of the coronary arteries. This is why LDL cholesterol is often referred to as the “bad” cholesterol.3
On its way back from the blood channels to the liver to be dismantled, cholesterol is transported by a larger sibling, the high density lipoprotein called HDL. HDL cholesterol makes it less likely that excess cholesterol in the blood will be deposited in the coronary arteries, which is why HDL cholesterol is often referred to as the “good” cholesterol.3
And this brings us back to fats. As I mentioned, the types of fats you eat determine your blood cholesterol level. So what is a fat? It’s mostly a chain of carbon and hydrogen atoms with a couple of oxygen atoms attached to the tail end. Carbon is the main player here, and because of the atomic structure of carbon, it is able to form four bonds to other structures. When you create a carbon straight chain you immediately fill two of the four spots for each carbon.4 That leaves two spots open. If you fill all the open spots with hydrogen, or saturate the structure with hydrogen, you’ve created a “saturated fat.”4
Dropping a couple of hydrogen atoms and using the extra spots to doubly connect two carbon atoms together creates what is called a “double bond.” Because several hydrogen spaces have been evacuated, an “unsaturated fat” has been created. If the chain has only one double bond, it is a “monounsaturated fat.” If the chain has two or more double bonds, it’s a “polyunsaturated fat.”4
Now, if you take an unsaturated fat with a double bond, heat it and add hydrogen, you can change the position of the hydrogen atoms at the double bond. Usually they are both on one side of the chain, but the chemical reaction causes one hydrogen to cross over to the other side of the chain so that the hydrogen atoms now sit across from each other. We call this a “trans fat,” because “trans” means across.4 We first started making trans fats when concerns surfaced about the health effects of saturated fats in butter. By hydrogenating vegetable oil – that is, adding hydrogen atoms to create trans fats – we discovered that liquid vegetable oil turned solid and could be sold as sticks of margarine.1 From the 1950s to the 1980s, we thought what we were doing was healthy. Tufts University nutrition professor Alice Lichtenstein says that back then “anything was good if it decreased saturated fat consumption. But then studies began to question ‘trans fats’ too.”5
Unsaturated fats, those with one or more double bonds, are good. They lower bad LDL cholesterol and raise good HDL cholesterol. Trans-fats, those liquid-to-solid hydrogen creations, are the evil twin. They raise LDL cholesterol and lower HDL cholesterol. Unsaturated fats lower rates of heart attack and stroke. Trans fats raise them.3
And finally, what about those saturated fats? Still bad, but not as bad as trans fats. Saturated fats raise LDL and HDL, but the net overall effect is more harmful than it is good.5,6
When it comes to managing your fat intake, it is all in the chemistry.
References
1. MSNBC.com. New York City passes trans fat ban. 5 Dec. 2006.
2. American Heart Association. Fat. 2008.
3. Harvard School of Public Health. Fats and Cholesterol. 2008.
4. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition. Questions and Answers about Trans Fat Nutrition Labeling. 8 Feb. 2008.
5. Mann D. Trans Fats: The Science and the Risks. WebMD. 6 July 2006.
6. Center for Science in the Public Interest. News Release. NAS Panel: Only Intake of Trans Fat is Zero. 10 July 2002.
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