High Confusion & Heart Disease in Women

A recent study came out observing a higher risk of heart disease within a 30k+ sample of Italian women who consumed higher carbs, or higher GI foods, or higher GL foods. What fascinates me is not the study itself, but the description of the results by both the press and the study authors themselves. More on that in a bit, first the study.

It was a cohort study. Take it with a grain of salt. A big one. The analysis for the women in the study concluded the following, ordered by relative risk:

1. women with highest GL [glycemic load] diets had a relative risk of heart disease of 2.24
2. women with highest total carbohydrate intake had a relative risk of heart disease of 2.00
3. women with highest GI [glycemic index] diets had a relative risk of heart disease of 1.68

Even though this study would seem to confirm my own biases, I think it's mostly worthless. It's an observational study that assesses diets based on questionnaires, so the data should be treated as highly unreliable. Given that, relative risks should be very high before we get too worked up. Relative risks around 2 in a study like this are pretty boring. (And fewer than 1 in 200 women developed heart disease over the course of the study, compared with greater than 1 in 50 men.) Useful only to generate funding for further studies. Not at all useful for guiding public health policy. So this isn't really worth so much attention in the press.

That said, I'm fascinated by how it was described, even by its own authors. There seems to be a real disconnect between the data and the editorializing. Let's review from a few lines above: total carb intake showed a greater risk than just GI. High GL, which is essentially a combination of the two, showed the highest risk. The risks of total carbs and high GL were close to each other, with high GI trailing in third farther behind. Naturally, the press coverage focused on GI.

The headline from the BBC explicitly and only mentioned "High GI". The Independent says "Sugary". The BBC article even rolls out these head-scratchers:

"high GI foods, rather than carbohydrates per se, appear to pose a risk"

and

"Low GI carbohydrates, such as pasta, which release energy and raise blood sugar far slower, showed no such link with heart disease."

Maybe I'm losing my reading comprehension skills. Let me look at the study again.... As I remembered, carbohydrates per se not only appear to pose a risk, but they appear to do so to a greater extent than high GI foods. Both of those statements are demonstrably false if you take the very study they claim to be about at face value. How's that for spin?

Worse, the actual authors of the study are being dishonest, saying,

"Thus, a high consumption of carbohydrates from high-glycaemic index foods, rather than the overall quantity of carbohydrates consumed, appears to influence the risk of developing coronary heart disease."

So the reporters are uncritically regurgitating how the study was described, rather than reporting on the study itself [likely the reporters never bothered to read the study], and the authors are misinterpreting their own results ["lying" is a strong word]. The study actually did in fact observe that "the overall quantity of carbohydrates consumed" influences the risk to a greater extent than high-GI foods does, yet the authors claim the opposite. Well, I'm baffled.

The only explanation I can come up with is that they've already decided carbs are good. Since most people keep protein intake within a fairly narrow range, the higher carb diet is the same as a lower fat diet, and vice versa. So in part what was observed was women eating more fat had lower risk of heart disease. This causes so much cognitive dissonance in the researchers they have to figure out a way to not say it. You already know the punchline, right?

"They could try broadening the types of bread and cereals they eat...."

That's right! Conclusion = Eat More Carbs!


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bbc article
independent article

P.S. The only thing missing from the coverage was a recommendation for women to take statins.