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expert reaction to series of systematic reviews and meta-analyses about dietary fibre and the risk of non-communicable disease

Research published in The Lancet shows that relatively high intakes of dietary fibre and whole grains could be causally linked to reduced risk of non-communicable diseases. 

Prof Kevin Whelan, Professor of Dietetics, King’s College London, said:

“The study published by Reynolds and colleagues draws together all previous studies investigating fibre and human health, and importantly they include both observational studies and randomised controlled trials. The researchers were able to look at 185 observational studies which recorded what people were eating in their everyday lives and then related that to whether they go on to develop disease over time – in total for 135 million person years. The researchers also looked at the results of 58 clinical trials of fibre, whereby people were given new diets and to investigate the effect on health and the results are able to show cause and effect relationships.

“The greatest reduction in risk of disease was when dietary fibre intake was between 25-29 g per day. Dietary recommendations in the UK are that the general public should eat 30 g per day of fibre, and so this national recommendation is consistent with the findings of this latest analysis. The challenge is that many people in the UK do not eat this amount of fibre. The major sources of fibre in the UK diet are cereals (bread, pasta, rice, breakfast cereal), vegetables and fruit. People should consider ways of increasing fibre intake through changing food preparation methods (e.g. not peeling potatoes), switching to wholegrain cereals (wholegrain bread, brown pasta) and replacing sugary snacks with fruits, vegetables, nuts and seeds.

“Importantly this research was able to investigate not only the effect of the total amount of fibre, but also the quality of the fibre. For example, wholegrain fibres were shown to have significant health effects whereas the evidence that low glycaemic index diets were effective were less convincing.”

Dr Ian Johnson, Nutrition Researcher and Emeritus Fellow, Quadram Institute Bioscience, said:

“This very comprehensive systematic review of published evidence on the relationship between the quality of dietary carbohydrates and human health confirms that diets rich in fibre provide real protection against a range of diseases including Type II diabetes, coronary heart disease and bowel cancer. The sheer volume of evidence, together with the consistency of findings from both observational studies and randomised controlled trials shows that we can now be very confident that a high consumption of fibre from all sources, and particularly from whole-grain cereals, provide significant protection against the common diseases of later life that now place considerable strains on the NHS.

“The greatest reductions in risk were seen at levels of intake of between 25g and 29g of fibre per day, a finding which is consistent with the current dietary recommendation from the UK government that adults should consume 30g of fibre per day, from a variety of foods including wholegrain cereals, fruits and vegetables.  It is a concern that the fibre consumption in the UK is on average, currently much less than this. It is also worrying that otherwise healthy consumers who try to follow popular diets low in carbohydrate will find it very difficult to achieve a healthy level of fibre intake.”

Prof. Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“I think this is an important paper which highlights better than before the potential value to health of higher dietary fibre intake. However, as with the vast majority of nutritional data, most of the evidence comes from observational studies and one has to be cautious about conclusions reached given the unavoidable biases they contain. That noted, this paper importantly also includes risk factor data from trials and the reductions in weight and other known causal risk factors such as blood pressure, cholesterol, etc seen with higher fibre (whole grain) diets, although modest do support the overall findings linking more fibre in the diet to less heart disease, diabetes, cancers, and potentially longer life. So I tend to believe the overall findings are directionally true and so concur with the authors conclusions when they write “recommendations to increase dietary fibre intake and to replace refined grains with whole grains is expected to benefit human health.”

Prof. Nita Forouhi, MRC Epidemiology Unit, University of Cambridge

“We need to take serious note of this study, based on a robust analysis and complementary findings from both observational and randomised trial evidence. This study effectively re-endorses that the UK Government advice to consume 30g fibre per day is pretty spot on. The onus is on individuals themselves, as well as public agencies, to make it happen, as average fibre intakes remain woefully low at a population level in the UK.

“This research did not study total carbohydrate intakes specifically, but its findings do imply that, though increasingly popular in the community at large, any dietary regimes that recommend very low-carbohydrate diets should consider the opportunity cost of missing out on fibre from whole grains. This research confirms that fibre and whole grain intakes are clearly important for longer term health.

“Ultimately this research provides a solid foundation that when it comes to carbohydrates, the quality matters very much, over and above the debate on quantity. Whole grain foods are typically high in fibre, and this research provides further evidence to highlight their importance and support a shift in our diets from processed and refined foods in the food supply chain towards more fibre-rich whole grain foods.”

*‘Carbohydrate quality and human health: a series of systematic reviews and meta-analyses’ by Reynolds et al. will be published in The Lancet at 23.30 UK time on Thursday 10 January 2019, which is also when the embargo will lift. 

All our previous output on this subject can be seen at this weblink:

Declared interests

Prof Kevin Whelan: “I have received research funding from government agencies such as the Medical Research Council, National Institute of Health Research, charities such as Helmsley Trust, Kenneth Rainin Foundation and Crohn’s and colitis UKL and industry bodies including the Californian Dried Plum Board, Almond Board of California, International Nut and Dried Fruit Council, Nestle and Danone.”

Dr Ian Johnson: “Until 2015 Ian Johnson was an external expert member of the SACN working group on Carbohydrates and Health.”

Prof. Naveed Sattar: “COI None.”  

Prof. Nita Forouhi: “I am a member of the Joint SACN/NHS-England/Diabetes-UK Working Group on ‘lower carbohydrate diets compared to current government advice for adults with type 2 diabetes’. Views expressed are my own, not the Group’s.”

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