Why The Latest Low Carb Scare Study is Flawed

You'll soon be hearing about a large scale epidemiological study of low carb diets and mortality published this week in Annals of Internal Medicine which purports to show that eating a low carb-meat based diet increases the incidence of mortality (i.e. death!).

Low-Carbohydrate Diets and All-Cause and Cause-Specific Mortality: Two Cohort Studies Teresa T. Fung et al. Annals of Internal Medicine September 7, 2010, vol. 153 no. 5 289-298

Here's why it's crap--and completely irrelevant to those of us who control carbohydrates to keep our blood sugars normal.

The methodology used here was this:

Prospective cohort study of women and men who were followed from 1980 (women) or 1986 (men) until 2006. Low-carbohydrate diets, either animal-based (emphasizing animal sources of fat and protein) or vegetable-based (emphasizing vegetable sources of fat and protein), were computed from several validated food-frequency questionnaires assessed during follow-up.

This raises four immediate red flags.

1.Based on Inaccurate Questionnaire Data. The standardized food frequency questionnaire used in nutrition studies is designed in such a way that it is impossible to gauge the actual food intake of people eating a true low carbohydrate diet.

It is a list of questions like, "How many times in the last month did you eat bread" followed by a multiple choice set of answers which are along the lines of "1 to 10 times" "11-25 times", "26-50" times "More than 50 times."

But the answers supplied for carbohydrate items do not allow for the possibility that the answer to a question like "How many times this past month did you eat bread" is zero or even five. Ditto potatoes. Ditto sweets.

I know first hand how inaccurate the standard food frequency questionnaire is because several years ago I was a subject in a long term study that used the standard nutritionist designed food intake questionnaire. During this time I was logging my actual food intake, with weighed portions, trying to understand my own pattern of weight loss, so I knew exactly what I was eating during any given day or month.

The nutritionist associated with the study emailed me the nutritional breakdown that I had supposedly eaten, based on my answers to the standard food frequency questionnaire. It bore no relationship at all to what I had eaten either in terms of calories or the percentages of my diet represented by protein, carbs, or fat. When I offered to send the study my actual food intake, I was told that the questionnaire they were using had been carefully validated and was standard in all nutritional studies and that there was no point in looking at what I had actually eaten.

If that isn't bad enough, the questionnaires rely on the memory of the people filling them out--who are likely to "forget" or downright misrepresent how often they ate foods they know are bad for them like sodas, snacks, and sugary desserts. It is well known that people give the answers they wish they were true on questionnaires like this where there is no way for anyone to check up on whether they are telling the truth.

Garbage in, garbage out. But since it is garbage that reinforces a religious belief nutritionists want to hold onto even though better designed studies do not support it, you will be seeing this study used to "prove" how unhealthy the low carb diet really is.

2.Misleading Definition of "Low Carb Diet" Leaving aside the fact that the data collection method renders the data highly questionable, the definition of "low carb" used in this study is almost certainly one most of us that eat a true carb restricted diet would consider a high carb diet--one of 150-200 grams of carbohydrates a day.

If that is the case, the "meat based" low carb diet was probably a "meat and potatoes and bread" diet, which we are all agree is not healthy for anyone.

3. "Meat-based diet" May Mean "Fast Food Meat and Potatoes Diet" All meats are not the same, but the standard food intake questionnaire makes no attempt to distinguish between fast food, chemical laced meat served with sides filled with trans fat and home cooked nutritious meals. The questionnaire only asks about how often the respondent ate "pork" or "beef," not where they ate it, or what cut they ate. Or most importantly, with what side dishes.

I have no doubt that eating a diet of fast food burgers (with the rolls conveniently forgotten when reporting "bread" intake") is quite capable of shortening life. But it is not because the person is eating a "meat based low carb diet" that they are risking their health.

4. "Plant based Low Carb diet" Highly Suspect The "plant based" low carb diet which was found to be so healthy here is unlikely to be low carb, since it is almost impossible to eat a true low carb diet relying on plant based foods without overdosing on soy which is far from healthy. This finding again points to the likelihood that the "low carb" diet is not low carb but moderate carb and that the plant eaters here are people who stay away from fast food outlets.

Once again, the nutritionists defending their turf use flawed methodologies to ensure that people with diabetes will continue to eat the "healthy whole grains" and sugary fruits that ensure they will end up with severe, life threatening complications.