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People who eat a diet high in fiber have significantly lower levels of a protein that is associated with inflammation, diabetes and heart disease, say scientists, giving yet more support for high-fiber diets.

C-reactive protein (CRP) is produced in the liver and is a known marker for inflammation. Increased levels of CRP are a good predictor for the onset of both type-2 diabetes and cardiovascular disease.

An estimated 19 million people are affected by diabetes in the EU 25, projected to increase to 26 million by 2030. CVD causes almost 50 per cent of deaths in Europe, and is reported to cost the EU economy an estimated €169 billion ($202 billion) per year.

The prospective observational study, Seasonal Variation of Blood Cholesterol Levels Study (SEASONS), used 24-hour dietary recalls to measure usual intake of carbohydrate, protein, fat and fiber. Over 500 participants with an average age of 48, took part in the year-long study.

“The likelihood of elevated CRP concentrations was 63 per cent lower in participants in the highest quartile of total fiber intake than in participants in the lowest quartile,” reported lead author Yunsheng Ma from the University of Massachusetts.

Insoluble fiber intake was associated with a 68 per cent reduction in CRP levels, while soluble fiber was linked to a 42 per cent reduction.

“This study suggests that a diet high in fiber may play a role in reducing inflammation and, thus, the risk of cardiovascular disease and diabetes. Our results support the current dietary guideline, which recommend 20 to 35 grams of fibre per day, including both soluble and insoluble fiber,” concluded Ma.

The mechanism of how dietary fiber could reduce inflammation is not clear, say the researchers. A recent review had suggested that fiber could reduce the oxidation of fats, which is linked to oxidative stress and increased levels of inflammation.

Another explanation is that soluble fiber act as prebiotics by boosting conditions for bacteria in the intestinal tract, improving gut health, and subsequently preventing inflammation.

The authors note some limitations of their study, most notably that the researchers could not control for medications in their study. Participants taking statins or hormones, for example, were excluded at the start of the study, but no checks were made during the study to check continued compliance.

Randomised controlled clinical trials of high and low-fiber diets are needed, said the researchers, and, based on the results of these trials, a review of public health recommendations.