Dear Dr. Toshi,
Should I be on a low-fat diet?
Now the experts say that the type of fat that you eat is far more important than the portion of calories you get from fat. We need good kinds of fat for proper body functions, after all. It's necessary for the absorption of certain vitamins, our energy, hormone production, health of our cells, and many other things. So, a low-fat diet is not necessarily the right answer. In fact, if you eliminate fat completely from your diet, you'd be in big trouble. So, in the next few articles, let's talk more about the different types of fats that are in our diet. I'd like to clarify some words and give you a very simple "bottom line" recommendation regarding dietary fat as we understand it at this point.
Medicine and science related to dietary fat turns out to be a very complex field of ongoing research. Not only that, it's quite confusing because there are so many difficult words that you may have heard about this topic. We're talking about dietary fat here (fat that we eat), but it's also closely related to things like cholesterol and the "lipid panel" lab (bloodwork) that you sometimes get for your annual physical exam.
Most food items in grocery stores (except for fresh produce and some meat and fish) have food labels that show their nutritional information. Have you ever noticed the fat content of the food on the label? In addition to "Total Fat," sometimes the labels list the various different kinds of fat such as "saturated fat," "polyunsaturated fat," "monounsaturated fat," and "trans-fat." Sometimes scientists call these fats "fatty acids." You've probably noticed that most food items don't just contain one kind of fat, but usually have a mix of different kinds of fat. The important thing is to choose foods that have more of the good kinds of fat than the bad kinds.
Basically, good fats are unsaturated, including polyunsaturated and monounsaturated fats. The worst fats are trans-fats. Saturated fats are sort of in between those two, but a little more on the bad side. You can eat some saturated fat, but you don't want to eat very much. I'll talk more about saturated and unsaturated fat in the next couple articles, but today I'd like to explain why trans-fats are the worst fats.
Trans-fat is much less common in food nowadays, but if you see it on a food label in a store, I'd recommend not buying it. Trans-fat is a kind of fat that's artificially manufactured from good "unsaturated fat" by a chemical process called partial hydrogenation. You may have seen "partially hydrogenated vegetable oil" listed in the ingredients of some foods. Trans-fat is easier to cook with and doesn't spoil as fast as natural oils, so companies like to use it in a lot of processed foods, including margarine, peanut butter, potato chips, crackers, microwave popcorn, and many other packaged snacks and pastries (including donuts) because it provides longer shelf life. Like I said before, it's now considered "not safe" by the FDA as of 2018, so it's close to being banned and a lot of products with trans-fats have been removed from the US food supply. I say, "close to" being banned because it's still out there. The tricky part is that companies are legally allowed to claim that their food has "No trans-fats!" and they can put "Trans-Fat 0 grams" on the nutrition label as long as it contains less than 0.5 grams of trans-fats. So, if you eat a lot of food with "0 grams trans-fat" in it, you may be actually eating quite a bit of this bad trans-fat without realizing it. If you aren't sure if a food has any trans-fat in it, look for the word "partially hydrogenated" in the list of ingredients, and avoid it!
Trans-fat (or trans-fatty acids) raise your bad cholesterol (LDL) and total cholesterol level, while also lowering your good cholesterol (HDL). (I'll talk more about cholesterol later, too.) That increases inflammation in your body and increases your risk of heart disease, stroke, and diabetes. It's also known to increase insulin resistance, which can lead to diabetes, and make existing diabetes worse. One study showed that if a person even gets just 2% of their total daily calories from trans-fats, it can increase their risk of heart disease by 23%!
One thing you should remember is this: Fats that aren't good for you tend to be solid at room temperature, like bacon grease, lard, shortening, coconut oil, butter, and margarine. And remember that it's important to avoid trans-fats by paying attention to food labels.
Dr. Toshiko (Toshi) Luckow, MD is a Family Medicine physician at the West River Health Services hospital and clinics.