Does low carb mean low fiber?

The Lancet study, which was published on January 10th 2019, was presented as such a definitive nail in the coffin of low carb diets that it deserves a complete rebuttal (Ref 1). Last week we noted that prospective cohort studies and meta-analyses of these studies have compared people who consume whole grain carbs with people who consume refined carbs. These population studies have not compared whole grain consumers with real food/low-carb consumers, not least because the latter way of eating is a recent phenomenon and the population studies that we rely on today date back to 1968.

One of the claims, which requires a full rebuttal, is the assertion that a low carb diet is a low fiber diet. A zero carb diet is a zero fiber diet, but there are so few people eating zero carb, that this will probably never be possible to assess in any population study.

The Guardian headline – “Blow to low carb diet as landmark study finds high fibre cuts heart disease risk” (Ref 2) – has been very interesting to examine more thoroughly:

Is a low carb diet a low fiber diet?

Back to the diagram from last week:

Box A contains food groups high in fiber and low in carbohydrate.

Box B contains food groups high in fiber and high in carbohydrate.

Box C contains food groups low in fiber and low in carbohydrate (with the exception of some carbohydrate in dairy, these foods are essentially zero fiber and zero carbohydrate).

Box D contains food groups low in fiber and high in carbohydrate. Box D also contains foods that don’t fit into natural food groups, because they aren’t natural foods – all junk is in Box D.