Yesterday, the NY Board of Health voted to ban trans fats -- after a phase-out period -- in restaurants in the city:
New York City's board of health on Tuesday voted to phase out most artificial transfats from restaurants, forcing doughnut shops and fast-food stands to remove artery-clogging oils from their cooking.
The law will require McDonald's and other fast-food chains that have not already eliminated transfats to do so by July 2007. They will be given a six-month grace period before facing fines.
Makers of doughnuts and other baked goods will be given until July 2008 to phase out transfats.
There is a lot of stuff I want to talk about related to this. First, I want to summarize what trans fats are. Second, I want to summarize the evidence that they are bad for you -- and that evidence is pretty strong. Finally, I will just tip my hand as to what I think about this whole business.
What are trans fats?
Fats are long chains of hydrocarbons attached to an organic acid -- hence they are sometime referred to as fatty acids. Saturated fats are chains of hydrocarbons that have all the possible hydrogens occupying all the possibly spots on the carbon chain. Thus, they have no double bonds in their carbon chain.
Here is an example of a saturated fat called myristic acid.
Unsaturated fats, on the other hand, do not have all the carbon positions occupied. As a consequence, they do possess one or more double bonds. Here is an example of an unsaturated fat called oleic acid.
You can see that the two parts of the double bond (indicated by the double line) are on the same side. This places a kink in the chain that prevents it from lining up straight. This is not always the case, however. Sometime the bond is aligned differently so that there is no kink. Take, for example, elaidic acid.
Elaidic acid has a double bond, but the two sides of the chain are oriented on opposite sides of the double bond. the nomenclature that we use for this is called cis and trans. When the chains are located on the same side of the double bond -- like oleic acid -- the fat is called a cis monounsaturated fat. When the chains are located on the opposite side of the double bond -- like elaidic acid -- the fat is called a trans monounsaturated fat.
What is the significance of all of this? Well, fat chemistry is all about stacking. Saturated fats and trans unsaturated fats form nice stackable chains. This means that when they are in your arteries, they can more easily congeal and form a plaque -- something with the consistency like butter. Cis unsaturated fats don't stack well. When they are in your arteries, they refuse to congeal -- leaving something more with the consistency of olive oil.
So you can understand chemically why scientists and physicians would be concerned with trans and saturated fats. The issue is not so much the absolute intake of fat, but rather what that fat does to your arteries when it is in your body.
Molecule of the Day had this post a while back on fat chemistry that is also really informative.
What is the evidence that trans fats increase the risk of heart disease?
- Willett et al used data from about 85,000 nurses from the Nurses Health Study followed prospectively, 431 of whom went on to have heart attacks. They found that after age and energy intake were corrected the relative risk between the highest and lowest quintiles for coronary heart disease (CHD) was 1.5. Regular intake of margarine -- a major source of trans fat -- increased the relative risk to 1.67. The high relative risk did not vanish even after controlling for other CHD risk factors, vitamin intake, or fiber intake.
- Ascherio et al employed a case-control design comparing 239 hospitalized patients with first admission heart attack with 282 controls. They found that after controlling for age, sex, and energy intake, the relative risk between the highest and the lowest quintiles was 2.44.
- Hu et al employed a huge prospective study following over 80,000 healthy women starting in 1980. Over that period, 939 of these women had heart attacks. The researchers found that for every 5% caloric intake from saturated fat there was a 17% increase in CHD risk (relative risk 1.17 as compared to the same number of calories from carbs). For each 2% increase in calories from trans fats there was a 93% increase in CHD risk (relative risk 1.93 as compared to the same number of calories from carbs). That means that for each 2% increase in calories from trans fats your heart attack risk nearly doubles. Monounsaturated and polyunsaturated fats were found to decrease risk.
Here is a chart to summarize the data from the Hu et al. paper. It shows what happens to the risk if you substitute a certain percentage (in most cases 5%) of calories from one food for another. This table is somewhat backwards as it always substitutes the good food for the bad food. Therefore, negative percentages suggest that the bad food substituted for increases your risk of CHD.
As you can see, substituting carbs for saturated fat lowers your risk -- suggesting that saturated fats raise your risk. The more interesting parts are below. If you substituted monounsaturated or polyunsaturated fats for trans fats, you rather substantially decrease your risk of CHD.
What do I think?
The evidence that trans fats promote CHD is solid. If I were a physician (and hopefully I will be someday), I would strongly recommend to my patients to avoid trans fats. I try and avoid trans fats myself.
What bugs me about this situation is that I don't feel comfortable with the government banning a food item that can be used responsibly. This issue is not like a food additive that causes cancer. Trans fats when used in reasonable quantities can be used without health consequences. And while I recognize that taste tests for most people reveal that they can't tell the difference, I don't think that the government should be involved in determining what tastes good enough and what should be put in my food. Where's it going to end? Fois gras is bad for you -- incredibly bad actually. Should I not be allowed to buy that either?
Also, this policy is almost certainly going to result in higher costs for New York restaurants over at least the short-term. It already costs a lot to eat here, and frankly I have no interest in paying added regulatory taxes.
If I were forced to confront this problem, I would deal with it this way. When people realized that MSG was bad for you in Chinese food, some restaurants started advertising that they had no MSG added to their food. People who were concerned about their health chose to start eating at those restaurants. People who preferred the taste stayed at the same restaurants. Slowly, the no MSG restaurants began to supplant the MSG-using restaurants because more people preferred them and they vote with their feet. I don't understand why this is not an acceptable remedy in this case. You can say to restaurants "Use whatever you want, but if it is trans fats you have to tell people." Then people can decide whether they want to eat there. I for one would decide to avoid restaurants that use them, but I can understand why people wouldn't care.
To summarize, I do not dispute the science. The science informs my decision. However, I don't see why the Board of Health needs to make my decision everyone else's decision.
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Damn, there goes all the great food in NY!
My real reaction, what a crock. I'll eat what I please, thank you very much.
What bugs me about a lot of the statements about the impact of trans fats is that they chose cis unsaturated fats as the substitute, which isn't likely to be the case. Saturated fats are more likely to be substituted for trans fats than cis unsaturated fats are because they have similar melting points and textures, especially considering that they've been used extensively as a replacement for applications that have historically used saturated fats (vegetable shortening for lard, margarine for butter, etc). Based on the Hu et al table entries above for trans and saturated vs unhydrogenated, unsaturated fats, a replacement of 2% of trans fats with saturated fats would reduce risk by around 40% (I'm eyeballing off the chart). Also, while a 2% reduction of trans fats as a calorie source may seem small, the FDA estimates that the average % of calories from trans fat for the US population is 2.6%. So for your modal American, every 10% replacement of trans fats without a substantial dietary change would be expected to reduce risk by 5%.
As it happens, fois gras is already banned in some places, although for reasons of animal cruelty rather than public health. Chicago, for instance, forbids the sale of fois gras.
I never know what to think of these medical studies. One half of one-percent of the sample in Willett et al had a heart attack. Trans fats raised the relative risk by 1.67. So that means for a baseline rate of a heart attack of 5 per 1000, trans fats raised that to 8 per 1000. Is that right? Cuz that doesn't sound like all that much to me.
If the numbers are valid, it's not. That's why quoting relative risks can be so deceptive. We see this in medicin all the time. Doubling the rate of a complication that only happens five times in a thousand means that the complication would then only happen ten times in a thousand, for example. The relative risk doubles, but in absolute terms it's still very small.
Personally, I think the NYC decision was pointless and probably won't make enough of a difference to be worth the bother. And, as was pointed out, what's next? Caffeine? Too much salt? People who eat food with a lot of trans fats aren't doing so with the expectation that it's good for them in general, particularly when it's eating fast food.