Last week I talked a little about some of the popular rumors about margarine in this post. I thought I could move on from this topic, but as there no shortage of "I'm not a medical professional, but I play one on the internet" floating around on social networking sites, I decided that wasn't quite possible just yet.
One of my friends decided to make a comment about a doctor recommending that he eat more butter. I try to stay out of things unless I am specifically paged, but then a comment was made about butter having "good cholesterol" and margarine having "bad cholesterol" and I knew I couldn't escape another opportunity to enlighten those who want to be enlightened.
Lets talk a little bit about what cholesterol is first. Cholesterol is a waxy lipid that is part of the lining of every cell in the bodies of animals, both the two legged and the four legged kind. Cholesterol is necessary for insulating our neurons (kind of like the insulation of a wire), it helps build and maintain the membranes of our cells, it helps us metabolize fat soluble vitamins, helps us produce bile (which helps us digest fat), and helps our body make the hormones needed for daily function. In other words, this substance is suppossed to be present in a certain amount in a normal, functioning, healthy body.
Most people think of cholesterol as something that there doctor checks levels of in their blood periodically, and that there are only two types--the suppossed "good" cholesterol (HDL) and the "bad" cholesterol (LDL). Well, that's not exactly the case. The acronym of HDL stands for High Density Lipoprotein and the LDL stands for Low Density Lipoprotein (and there is also a VLDL, Very Low Density Lipoprotein). Now, if you take a look at those labels you will hopefully notice that lipoprotein is part of every label, but cholesterol is not. That's because all those little labels are suppossed to signal a particular substance that has the JOB of carrying cholesterol. So LDL and HDL aren't bad by themselves, they are just doing their job of carrying a vital body substance.
Now the problem seems to come when abnormalities develop in the LDL and VLDL and the amount might be indicative of later problems too. Why do people develop abnormalities in their shuttles or have more of them. Well, one reason seems to lie in our genetic history, some people for whatever reason tend to produce more smaller dense LDL. The other reason lies in our diet, which is where things get a little messy, and I am going to do my best to summarize.
Since roughly the 1970's, although some might argue a little earlier, we in the medical community have argued that to lower the amount of LDL and VLDL cholesterol you needed to limit saturated fat and total fat intake (and watch your calories), which was essentially based on observational research done by Ancel Keys. There were inklings that the research was flawed, but at the time that was the best advice we had. Now, just because someone was concerned with their risk of heart disease didn't mean that they wanted to give up taste necessarily, so people starting using a lot more unsaturated oils and also filling in the gap with a lot of low nutrient carbohydrates. (Anybody remember the favorite "diet" meal of the 1980's and 1990's consisting of a baked potato with low fat sour cream?) None of that helped--as many people ignored that their low fat items often contained the same amount of calories, and if they weren't getting enough protein and fat they didn't feel full, and likely ate more. All of these things together likely contributed to burgeoning waistlines, which in turn by itself increases LDL. The increase in vegetable oils might contribute to an excessive intake of omega-6 fats, which might contribute to inflammation, and the body will start shuttling more cholesterol to "heal" the inflamed arteries (hence more LDL). And the overconsumption of refined carbohydrates can lead to elevation insulin levels, also possibly triggering inflammation, and therefore, more LDL.
Like I said, that was a summary, there is a whole lot more involved, but some of it gets on shaky ground as far as consipiracy theories about Big Pharma, etc. But the moral of the story is that what a lot of people thought they were doing to lower their LDL levels backfired, and it also explains why people on low carb diets where able to improve their lipid profiles despite eating a lot of animal fat--they reduced their caloric intake, lessened their intake of omega-6, and they reduced their insulin levels.
But what about the people who went vegetarian or vegan and also claim lower weight, lower LDL, etc? I think the explanation lies in the type of plans people follow when on they are on a controlled study, in other words, the study diets would have limited the caloric intake and helped with the weight. They would have been low in fat, and quite possibly contained nuts and flax when fat was allowed, and they may have gotten a few more omega-3's and less omega-6's, and they still would have likely excluded the added sugars and the processed white bread, etc, meaning that they wouldn't raise insulin levels as much. Now, when I was vegan, I like to think that I ate more like the "study diets" and I was able to keep my lipid profile in great shape and my weight under control for the most part (It didn't, however, take care of my GI problems, which is another story) But we all know the people that cut out the animal foods only to pig out (that's a scientific term) on pasta and soy burgers and barely pick up a vegetable ever.
So what can we agree on from a scientific standpoint so far? Limit or avoid added sugars, limit or avoid refined starches, limit or avoid trans-fats, control your portions, consume animal protein that is as close to nature as possible, keep your animal fats as close to nature as possible (to get more omega-3s), limit or avoid processed vegetable oils, be careful about your alcohol intake, don't smoke, and control your portions. Or as Michael Pollan said--"Eat food. Not too much. Mostly plants."
So, if you are still with me, let's go back to the butter having "good cholesterol" and margarine having "bad cholesterol." First of all, margarine is not an animal product so it couldn't have cholesterol in it to begin with, nor does it contain low density lipoproteins either. Second of all, dietary cholesterol does not raise the LDL, so the cholesterol (not lipoproteins) in butter does not affect you. Third, trans fat does raise LDL, but most margarines/spreads these days are trans-fat free. Fourth, if you consume your butter on a pile of pasta/white rice/white bread (aka refined carbs), you are likely going to have trouble with your weight, LDL levels, and your triglycerides.
Take home message--The cholesterol found in food is not the same as the liproprotein carriers that are often misnamed as a type of "cholesterol." And if you are using butter, watch what it's going on on what it's going along with.
Links:
Cholesterol and health
http://www.nmsociety.org/
http://www.nytimes.com/2008/01/27/opinion/27taubes.html
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