Low-Carb Diet Study: But Wait, There's More!

Sometimes, even after you think you're done with crunching numbers in a study, the data somehow manages to keep mulling around in your head, teasing you to come back and take another look, quietly nagging at the back of your brain that there is something else, something important, go back and look again.

After reviewing the recently published Low-Carbohydrate-Diet Score and the Risk of Coronary Heart Disease in Women in the November issue of the New England Journal of Medicine, I posted Spinning Low-Carbohydrate Diet Study Data to highlight the headlines that claimed a low-carbohydrate diet rich with plant-based fats and protein had no basis in the data. If you read that article, you may recall I noted the finding of reduced risk was in the context of a dietary pattern where the lowest intake of carbohydrate was 202g each day compared with the highest of 242g each day. Not exactly low in carbohydrate and not exactly a remarkable difference in intake between the lowest and highest intake groups.

As I noted, in the context of an intake range of 202g to 240g carbohydrate, when subjects are consuming similar intake of red meat, chicken, fish - a higher consumption of nuts, coffee, saturated fat and whole grains with less fruits and vegetables may provide a benefit in the context of such a dietary pattern higher in carbohydrate.

But, at the time, it seems I missed something even more important than these very subtle differences between the groups. After my brain was insisting I return to the data, I went back, and something important (at least I think it's important) popped out - there was something remarkably different between the groups, more important than the differenece in consumption of nuts, red meat, coffee, alcohol, fruits and vegetables - the group consuming 202g of carbohydrate, the one with the reduced risk of cardiovascular disease, appears to have consumed enough polyunsaturated fatty acids (PUFA) to meet essential fatty acid (EFA) requirements; the group consuming 242g of carbohydrate each day didn't come close.

Intrigued?

I was!

So I went to the Institute of Medicine documents I have on file to double-check my memory about the level of intakes considered absolute minimum requirements for a female adult. Setting aside any arguement about exact ratios of omega fatty acids and any arguement of needing more omega-3 in the diet and less omega-6, sure enough, the IOM document includes a requirement that the group with reduced risk potentially met. Females, aged 31-70+, require between 0.6-1.2% of daily calories from omega-3 fatty acids and between 5-10% of daily calories from omega-6 fatty acids; with an absolute minimum requirement (regardless of calorie intake) of 1.1g of omega-3 and 11g-12g of omega-6 (females aged 31-70+); a absolute minimum of 12.1g-13.1g of essential fatty acids each day.

Essential fatty acids are found only in polyunsaturated fats, so to meet requirements one would have to consume more than the minimum requirement of polyunsaturated fats since not all polyunsaturated fats are essential fatty acids.

The group consuming 242g of carbohydrate each day only had 4.4% of their daily calories from PUFA - below the minimum requirement of 5.6% just for EFA from polyunsaturated fats. Taking it one step further, the 4.4% of calories worked out to just 8.5g of polyunsaturated fats each day - well below the minimum 12.1g-13.1g for EFA from polyunsaturated fats.

Compare that to the group with the 30% reduction in risk for cardiovascular disease - the group consuming 202g of carbohydrate - their diet included 7.4% of calories from PUFA, enough to meet the target intake of 5.6%. Taking it one step further, the 7.4% of calories each day worked out to 14.6g of polyunsaturated fats each day - enough to meet the 12.1g-13.1g minimum for EFA from polyunsaturated fats.

Big difference, isn't it?

In fact, if we look at each analysis - the total calorie analysis, with statistically insignificant differences between groups, they had minor differences between them for PUFA intake in absolute grams - 10.7g in the highest carbohydrate intake compared to 12g in the lowest carbohydrate intake; the animal calorie analysis showed 11.5g in the highest carbohydrate group compared to 10.3g in the lowest carbohydrate group.

The group with the real difference in PUFA intake was the plant-based calorie analysis, within this analysis the group with the lowest risk consumed much more PUFA - enough to theoretically meet essential fatty acid requirements when compared to the group at the other end of the spectrum whom did not consume enough to even come close to meeting requirements.

What increased PUFA intake in the group with reduced risk? That question leads back to the consumption of nuts, the one food the group ate significantly more quantity of. Nuts have repeatedly been assoicated with a reduced risk of heart disease and in this study, it seems they provided the boost to essential fatty acids that are necessary for overall good health.