Is Low-Carb Killing Swedish Women?

MPj04384870000[1]A recent Swedish study suggests that low-carbohydrate/high protein diets increase the risk of cardiovascular disease in women.  I’m not convinced, but will keep an eye on future developments.  This is a critical issue since many women eat low-carb/high protein for weight loss and management.

Researchers followed 43,000 women, 30-49 years of age at enrollment, over the course of 16 years.  In that span, they had 1270 cardiovascular events: ischemic heart disease (heart attacks and blocked heart arteries), strokes, subarachnoid hemorrhages,  and peripheral arterial disease.  Food consumption was estimated from a questionnaire filled out by study participants at the time of enrollment (and never repeated).

In practical terms, … a 20 gram decrease in daily carbohydrate intake and a 5 gram increase in daily protein intake would correspond to a 5% increase in the overall risk of cardiovascular disease.

So What?

To their credit, the researchers note that a similar analysis of the Women’s Health Study in the U.S. found no such linkage between cardiovascular disease and low-carb/high protein eating.

The results are questionably reliable since diet was only assessed once during the entire 16-year span.

I’m certain the investigators had access to overall death rates.  Why didn’t they bother to report those?  Your guess is as good as mine.  Even if low-carb/high protein eating increases the rate of cardiovascular events, it’s entirely possible that overall deaths could be lower, the same, or higher than average.  That’s important information.

I don’t want to get too far into the weeds here, but must point out that the type of carbohydrate consumed is probably important.  For instance, easily digested carbs that raise blood sugar higher than other carbs are associated with increased heart disease in women.  “Bad carbs” in this respect would be simple sugars and refined grains.

In a 2004 study, higher carbohydrate consumption was linked to progression of blocked heart arteries in postmenopausal women.

It’s complicated.

Steve Parker, M.D.

PS: I figure Swedish diet doctor Andreas Eenfeldt would have some great comments on this study, but can’t find them at his blog.

Reference: Lagiou, Pagona, et al.  Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study.  British Medical Journal, June 26, 2012.  doi: 10.1136/bmj.e4026


Filed under Carbohydrate, coronary heart disease, Heart Disease, Protein

3 responses to “Is Low-Carb Killing Swedish Women?

  1. Good post; interesting study – thanks! I think I’ll be keeping an eye on this too.

    Re your question, “I’m certain the investigators had access to overall death rates. Why didn’t they bother to report those? ” …

    Often a study is designed to only show significance for CV events rather than the more challenging CHD mortality or, harder yet, total mortality. To reach significance in the latter requires many more subjects and so is much more expensive.

    Just to be clear, consider the following (completely fabricated imaginary case): You want to study how a new type of parachute has affected skydiving mortality. If you limit your study to skydiving accidents among skydivers, you might be able to see a change in recent years. But if you look at total mortality, you will never get enough data to see a change.

    • Hi, Dan. You may be right.
      Sweden has a nationalized health system and I’d be surprised if it’s not computerized and coordinated with a death registry. After studying 40,000 women for 15 years, I they should have some significant numbers for the low-carb vs high-carb groups.
      It’s quite possible the researchers are hoping to publish the mortality numbers in a different paper. Many academic types have to publish or perish. It makes sense for them to milk the data for as many papers as possible.

  2. Dr. Parker:

    Thanks for tracking this and commenting on it. There is such a swirling mess of comment, supposed “facts” and leaping to conclusions on statistical anolilies verus actual probing research to see if the statistical “linkages” bear fruit.