I was having a conversation just yesterday with a patient of mine about alcohol consumption and wandered off into the interesting land of statistics and relative risks of dying. Evidence is accumulating that suggests the same kind of survival curve holds for dietary fat intake.
For the last several years, doctors have been aware that having a little alcohol in a daily diet has been helpful in controlling cholesterol. It promotes and increase in the good cholesterol and tips the ratio of total cholesterol to good cholesterol toward decreasing heart disease. Cynical conspiracy theorists might suspect doctors of not promoting this because it doesn't add to their bottom line and isn't promoted by the big pharmaceuticals, but I would dispute that. After all, the big liquor and alcohol manufacturing firms aren't pushing it either. Doctors have just had far too much exposure to the devastation and waste caused in their patient's lives due to the ravages of alcohol addiction. None of the other substances we know to reduce cholesterol are addictive.
Beyond addiction, drinking too much alcohol can lead to almost impossible to control high blood pressure in some people. Maybe some day we can predict who will start alcohol and end up with an addiction or hypertension, but that day isn't here yet. So for now, no doctor is promoting it very vigorously.
So where do risk of mortality curves come into this picture? What we're talking about now is risk of dying comparing different levels of some factor going from zero to a lot. The mortality (as in the death) is from all causes, not just one specific cause, like, say, cirrhosis. The picture for alcohol shows that the relative risk for all cause mortality DROPS when you go from no alcohol to 1 drink per day. It might even drop a bit lower at 2 drinks per day. After that, it just shoots right up. That suggests that, if you can manage it, having 1 or 2 drinks a day will actually serve you better than not drinking at all. The caveat, of course, is: can you manage it.
Here's the current recommendations for adults: no more than 2 drinks a day for men, no more than one drink a day for women. This gets important as you get older, too, because your ability to metabolize the alcohol decreases.
There's more and more evidence that fat follows a somewhat similar pattern. For the past several decades, the western medical world has been in the grip of a fat phobia. True, we've all been aware that you can't eliminate it entirely. After all, cell membranes are made up of phospholipids (read: fats) and cholesterol, and some of the crucial vitamins, like A, D and E, are fat-soluble, not water soluble. There are a few fats that we MUST get from diet, since we can't make them ourselves. Still, the feeling was the less we took in, the better we would do. This includes reducing risk for heart disease and cancers.
But is that true? The evidence is mounting that fat, like alcohol, is better in moderation, as opposed to too much or too little.
In the late 90's I saw some interesting research on the effects of diet on the HDL ("good") cholesterol of otherwise healthy young men. It was a real eye-opener. In this study, young men were put on one of two diets. The first was a 20% fat diet (for those of you who don't count your fat percents, that's quite low for the U.S.), and the second was a 30% fat diet, but fats like olive oil were substituted for saturated fats. Both groups had a drop in cholesterol, BUT---the low fat men had a significant drop in their HDL levels, which wasn't a good thing at all.
I've seen the effect myself, in my own personal experiment. I had been eating a low fat diet until May of 2001. Not only was I heavy (far, far, far too many calories, most of which were carbohydrates. Did I mention I was doing low protein as well?), but my HDL was in the toilet at 29. Now, I'm a woman. This wasn't just low, it was dangerously low. My total cholesterol was really low, and my LDL was under 100, but that generally doesn't compensate. Out of desperation, I went on the Atkin's diet, with a massive increase in protein and drop in carbohydrates. As for the fats, I'm not a big fan. I suspect I went back to the 30% level. To be frank, fat tastes best when combined with tasty starches, like bread, potatoes, or lost in cookies. Not too many people can tolerate butter on their steak. Yes, my cholesterol went up, but then so did my HDL. At this point, stable on a diet with a healthy amount of fat, my HDL is consistently above 60.
Now, a recent study has come out that shows a low fat diet might have a very mild effect on reducing breast cancer risk, but almost no reduction of risk in anything else. At least in adults. Frankly, I would be a bit leery of dropping fat content in diet down too low in growing children, since they need crucial nutrients to grow. Far better to reduce their soda intake, in my mind, since the risk of diabetes from too much sugar, too little exercise and too much obesity is far greater than some more distant cancer risk. Well, except for french fries.
Yes, french fries. That wonderful confection made of potatoes and fat. Apparently, the more little girls eat french fries growing up, the higher the risk of breast cancer. Not sure what's up with that, but since the risk was specific to french fries and didn't apply to hot dogs or other weird, fatty foods, I suspect it had more to do with the combination than with either fat or carbohydrate alone. Oh yeah, and the extra carcinogens that get produced when you fry carbohydrates at high temperatures.
Interestingly, a study in Scandinavia found that women who ate a lot of dairy fat were less likely to get colon cancer. This was separate from any calcium effect, too.
No, no one has done a study on all-cause mortality risks and dietary fat content. Some of that is because it's a little harder to exactly measure fat content in someone's diet, since the fat is blended in everywhere. I suspect type of fat used has an effect as well. But studies do seem to point to the advantages of moderation and the disadvantages of going to extremes in either direction.
My advice? Stick to about 30% fat in the diet, but make sure it's the good stuff. Go gourmet, not gourmand. Nut oils, olive oil, fish oil, that new Enova oil, and some of the new spreads that are low on trans-fats are fine. A little dairy fat here and there is probably ok as well. And keep the calorie count low, too. Fat in the diet may not kill you any faster, but fat in your belly surely will.
