Low Carb or Slow Carbs? Fiber Matters

In the midst of popular frenzy about low carb diets, substantial evidence suggests a shift in focus to us. Research is suggesting that slow carbs might be a very good option. Soluble fiber slows the digestion of carbohydrates. It gives food a lower glycemic index, meaning that it produces less of a spike in blood sugar. Fiber can also have helpful effects on gut microbes. So thus it makes sense that new studies are confirming fiber can be helpful for managing weight. Also for reducing the risk of chronic diseases.

Viscous Fiber and Weight Management

Viscous fiber is a type of soluble fiber that forms a gel when it dissolves in the gut. In the American Journal of Clinical Nutrition, Elena Jovanovski and colleagues have a new paper documenting the value of such fiber. They find it can help people lose weight – even without calorie restriction. Theirs is a systematic review and meta-analysis of 62 randomized controlled trials with 3,877 subjects. The authors conclude:

Dietary viscous fiber modestly yet significantly improved body weight and other parameters of adiposity independently of calorie restriction.

Alongside this paper, Mads Hjorth and Arne Astrup suggest that this effect may be due to more than the effect of this fiber on glucose and insulin responses to food. “Recent evidence suggests that most of the health effects observed in response to dietary fibers are mediated via the composition of the microbiota,” they write.

They note further that these benefits surely vary widely. So the next step is to find who can benefit most.

Broader Implications for Health

In a series of systematic reviews and meta-analyses last year, Andrew Reynolds et al found broad implications for health outcomes. They published their findings in Lancet, where they wrote:

Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre. Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g. Dose-response curves suggested that higher intakes of dietary fibre could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer. Similar findings for whole grain intake were observed.

From all of this we have good reasons to think that perhaps the quality of the carbs we eat is just as important as the quantity. Some of the energy that goes into chasing a low-carb diet might do more good if it went into slow carbs. Meaning more soluble and viscous fiber.

Click here for the Jovanovski study and here for the commentary. For the study in Lancet, click here. And for further perspective, click here.

Blueberries, Cherries, and Oatmeal, photograph © Ted Kyle / flickr

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January 14, 2020