Omigosh! A huge Swedish study proves that a low carb diet causes high cholesterol! We’re all going to die of heart disease. Oh, nooooooo!
It all sounds so very familiar. Here’s what I’ve been able to gather about this oh-so-scary study:
- Yes, the study spanned 25 years. And it involved 140,000 “measurements and questionnaires” – though that doesn’t tell us how many people were involved, or if the same participants were involved over the whole course of the study. Still, sounds important. But…
- It is a observational study. Most nutritional studies are observational, because they’re far cheaper and easier to do than clinical studies. By definition, observational studies never prove anything. Period. Why? Because they’re not controlled in any way. There’s absolutely no way of telling what confounding factors have affected the subjects – like, say, the fact that the Swedish population is aging. (And if the study did, indeed, use the same participants all along, they’re all 25 years older than when it started. Funny how that happens.) Observational studies are useful for suggesting avenues for more controlled studies, and that is all.
- This particular observational study depended, as so many of them do, on food frequency questionnaires. Remember what you ate for lunch three weeks ago last Tuesday? Yeah, neither do I. Food frequency questionnaires are notoriously inaccurate.
- Still, those questionnaires did suggest that Swedes, on the whole, reduced their fat intake a bit in the late ’80s. Consumption held steady for several years, then headed up again in 2004, after positive reports of the results of low carb/high fat diets came out. Higher total cholesterol levels followed about three years later. How high? An average of 5.5 millimoles per liter of blood, or in American terms, 213. Oooo, scary. Interestingly, when the study started back in 1986, average total cholesterol was 6 millimoles per liter of blood, or 232. It dropped, then came back up.
- The study conspicuously lacks any information about the breakdown of that cholesterol – nothing about LDL/HDL ratios, nothing about big, fluffy, protective LDL versus small, dense, atherogenic LDL. Nothing about triglycerides, either. Total cholesterol by itself is nearly meaningless to a low carb diet. It is entirely possible that the participants risk profiles have improved. We simply don’t know.
- The popular press is blaming the increase in Swedish saturated fat consumption, and therefore the mild rise in total cholesterol on the Atkins Diet. However, the average participant was eating 45.9 percent of their calories from carbohydrate. Doesn’t sound very low carb to me (definitely not the Atkins diet). Concluding anything about the Atkins Diet, or Low Carb/High Fat as recommended by Dr. Andreas Eenfeldt, from the effects of this diet is either stupid, dishonest, or both.
- In this study, the foods associated with increased saturated fat consumption included “fats used for spreading on bread and cooking, dairy products, oil for salad dressing or cooking, various types of meats, and sausages, as main dishes or on sandwiches, pizza, deep fried potato chips, French fries, including corn chips and popcorn.” Pizza? Potato chips? French fries? This could explain why the increasing saturated fat intake and cholesterol levels were accompanied by increased BMI.
- There is absolutely nothing in this study about an increase in atherosclerosis or in heart disease deaths. Indeed, Dr. Eenfeldt points out that the rate of heart disease in Sweden has not increased.
In short, this study suggests that perhaps in the context of a high carb diet, increasing saturated fat intake may raise total cholesterol, but does not tell us if that rise is comprised largely of LDL or HDL. It demonstrates no increase in atherosclerosis as a result. It doesn’t tell us anything about the effects of a low carb diet, because there’s no mention of anyone in the study actually eating a low carb diet. And because it is an observational study, it proves nothing. Nothing at all.
I suggest we all go back to our steaks.