22 January 2007
Trans Fats And Fertility
by Serena Mackesy
The media has been abuzz with a new health scare to bludgeon women with - "Food Fats Threaten Women's Fertility." But can dietary fats really turn your womb into a barren wasteland?
The source of the brouhaha turned out to be a recent academic study about trans fats and fertility rates, but here's the thing: fat isn't bad for you. It never was. For proper brain function, bone formation, mood regulation, yada yada, you still need to be making up 30 percent of your daily diet from fats and your kids need slightly more. It's not fat per se that puts weight on you, either: it's high calorific content.
Which is one of the problems with fast and convenience foods: if you haven't made it yourself, you will find it very difficult to judge how calorific a piece of food is, or know what proportion is actually fat. People who bake from scratch, for instance, tend to shove fewer cakes in their mouths than people who buy them from shops, for the simple reason that they can't kid themselves that, just because their sponge is light and fluffy, it must have the same calorific content as clouds, or kittens. Food labeling doesn't help, as it often refers to the calorific and fat content of "portions" rather than the whole thing, thereby making it seem less fattening, to someone scanning the label in a hurry, than it actually is. A single muffin, for instance, can contain anything up to four portions. As if anyone has ever bought a muffin for breakfast that lasted the next four days.
Anyway, the point with fats it that, like animals, some are more equal than others. Generally speaking, fats that are liquid at room temperature - the poly- and monounsaturated fats, which have a lower hydrogen content than the saturated ones - are good for you and lower your blood cholesterol. Saturated fats are solid at room temperature, like butter and the fats in red meat, and should be eaten with a bit of restraint, as they tend to raise blood cholesterol. But they're not actually evil, just generally better in moderation, like tequila.
And then there are trans fats. Contrary to popular belief, trans fats aren't entirely unnatural. they do, in fact, occasionally occur without the help of machinery; as a product of some fermentation process in grazing animals and also as a result of repeated reheating of cooking oil, as in deep-fat frying. But most trans fats are the result of forcing extra hydrogen atoms to adhere to the unsaturated fatty acids in vegetable and fish oils to produce a solid fat which a) can be used in place of butter in commercial cookery as a money-saver; and b) extend the shelf life of said products. Now, a lot, lot, lot of research has shown that these artificial fats are nasty, nasty, nasty; that they really are cholesterol time-bombs. If KFC are banning them from their foods, you have to know they're nasty.
But here's the thing: the American Journal of Clinical Nutrition recently published a study by the Harvard School of Public Health that's resulted in the sort of hysterical headlines the media thrive on. The claim is this: in a study of 18,555 women who were attempting to get pregnant, some correlation was found between consumption of trans fats and raised levels of infertility. In a follow-up, 438 incidences of ovulatory infertility were reported - interesting in itself, as the way the media goes on you'd have thought infertility was afflicting the majority of the population rather than roughly 3 percent of it - and of those, each 2 percent increase in the intake of energy from trans unsaturated fats, as opposed to that from carbohydrates, was associated with a 73 percent greater risk (that's 73 percent of 3 percent, of course), of ovulatory infertility. The same could also be seen among those who increased their intake of trans fats over monounsaturated fats.
Now, lone voices are already starting to cry in the wilderness about this study. Marion Nestle, a professor in the department of nutrition, food studies and public health at New York University, has pointed out that this increased risk was only able to be shown when the study adjusted for many other possible infertility risk factors. "If you look at their raw data, it just didn't show an increase in risk," she says. "And even when the adjustments were made, the numbers were still very small." She goes on to add that the only real link between food consumption and fertility so far properly established is this: that if someone is obese, or seriously underweight, their chances of failing to conceive skyrocket.
Should you be adding another reason to panic to your list? Well, if you've already worked out that trans fats are seriously yuk and cut down on ways in which you're going to be allowing them into your body, then probably not. If you haven't, then I would seriously advise you start looking out for the word "hydrogenated" on your food labels. And try to keep your general intake of fats down to between five and eight teaspoonsful a day: which, if you cook at all, you will know is entirely possible without any sense of deprivation. After all, it's all very well being able to conceive, but if you keel over with a heart attack while your bub's still in its infancy, it's not what we'd call a good result all round, is it?