John Cummings

Emeritus Professor of Experimental Gastroenterology

School of Medicine

Portrait photo of John Cummings
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John Cummings is Emeritus Professor of Experimental Gastroenterology in the University of Dundee. He is a member of the University’s Division of Cancer Research in the Medical Research Institute and was Honorary Consultant in Gastroenterology and Nutrition at Ninewells hospital until 2007.

He graduated in medicine in 1964 and after undertaking specialist clinical training in gastroenterology, joined the staff of the Medical Research Council in London. He worked for the MRC for 28 years, firstly, at the Gastroenterology Unit and, latterly, at the Dunn Clinical Nutrition Unit in Cambridge. His primary research interests have been in digestive physiology and disease and, particularly, the role of the gut microflora in determining gastrointestinal function and the prevention of cancer and bowel diseases. He has published over 300 papers and articles on this subject and is particularly known for his pioneering work on carbohydrates, dietary fibre and, more recently, the importance of intestinal bacteria to large bowel function. He moved to Dundee in 1999.

John Cummings has served on many national, European and international bodies concerned with diet and health, including the UK Government’s COMA committee, Scientific Advisory Committee on Nutrition, Dietary Reference Values Panel, Panel on Novel Foods and DH/FSA Nutrient Profiling Advisory Committee. He was a member of the IUNS Diet and Cancer Committee and of the FAO / WHO Expert Consultation on Carbohydrates in Human Nutrition (1997) and their scientific update on carbohydrates in human nutrition. (2006) He chaired the PASSCLAIM (EC concerted action) working group on gut health and immunity and was a member of the Consensus Group, which drew up criteria for substantiation of health claims on food in 2005. He is presently a member of the WHO Nutrition Guidelines Advisory Group on Diet and Health.

In 1993 Professor Cummings was awarded the Caroline Walker Science Prize and the Cleave Trophy in recognition of his work on public health aspects of diet. In June 2008 he was made an OBE in the Queen’s birthday honours for his services to medicine and nutrition and awarded the British Nutrition Foundation Prize in the same year. In May 2009 he was made an honorary PhD by the North West university in South Africa for the work he has done with them in establishing a department of nutrition over the last 25 years. He was the Rank Prize Funds Nutrition Prize winner in 2012 “For his outstanding work that established the role of the colon in human health”.


Professor Cummings’ early work concerned the importance of the intestinal microflora to large bowel function, when with Drasar and Hill he investigated effects of diet on the microflora and its metabolism using classical bacterial taxonomic criteria. These studies, which started in the formative days of the dietary fibre hypothesis when many interesting though unsubstantiated health claims were being made for fibre, laid the foundations for subsequent investigations on diet, the microflora and large bowel diseases.

With Southgate and James he demonstrated, in controlled human feeding studies, the importance of plant cell wall polysaccharides (fibre) as a major dietary factor controlling large bowel function through its effect on the microflora and with Jenkins the relation of fibre to the control of blood cholesterol. The mechanism of action of fibre in the large intestine was shown with Stephen by in vitro modelling and in vivo controlled dietary studies, to be exerted through its breakdown by the resident microflora and increased production of bacterial cell mass. From these studies, the concept of fermentation in humans was developed, in which anaerobic bacteria colonising the large bowel metabolise dietary carbohydrate, with the resultant production of short chain fatty acids (SCFA), H2, CO2 and biomass. This led to recognition of the importance of the colon as a digestive organ in salvaging energy from carbohydrate not absorbed in the upper gut. The mode of energy salvage by the large bowel was shown to be primarily through absorption of SCFA, and study of their physiology and metabolism was subsequently a major part of the Group's work. With McNeil and James their absorption from the colon was shown, uptake into portal blood (with Pomare) and differential clearance of butyrate by the colonic epithelium, propionate by liver and acetate by peripheral tissues. In metabolic studies (with Scheppach and Elia), acetate was demonstrated to have no effect on glucose metabolism or insulin levels in blood, and for organs other than the gut, probably liver, to be a source of acetate during starvation.

Calculation of daily production rates of SCFA and their stoichiometry led to the conclusion that there were substrates other than fibre being fermented in the colon. During work (with Englyst) on a method for measuring dietary fibre as non-starch polysaccharides (NSP), starch that resisted pancreatic amylase was first identified and called resistant starch (RS). A series of human and in vitro studies followed in which the rate and extent of starch breakdown in the gut was shown to be critical to its physiological effects. A new classification of starch for nutritional purposes was devised, together with analytical methods to back it up, both of which are now widely used in nutritional research. This work on NSP and RS, and more recently on oligosaccharides, has provided the impetus for nutritionists, and other scientists to their taking a new look at dietary carbohydrates as a whole, and the realisation that they constitute a macronutrient group with widely contrasting physiological properties and health benefits. Together with studies of bowel habit and bowel cancer (see later), this work formed the basis for the UK Department of Health recommendations on dietary NSP intakes and for the new proposed classification of dietary carbohydrates by the WHO/FAO Expert Committee on Carbohydrates in 1997. This has led to a new definition of dietary fibre being adopted at Codex in 2009, in which we played a major role.

In 1984, the Gut Group was joined by G.T. Macfarlane and later (1987), by G.R. Gibson, both from Dundee, to undertake specialist studies of the microflora and their metabolism. In addition to carbohydrate fermentation, during the study of which it was shown that RS was an important source of butyrate in the colon, the intense nature of proteolytic activity in the large bowel was observed, and marked regional differences in microbial metabolism were shown to be consistent with patterns of colonic disease. The recent demonstration that nutrient availability is a major factor in controlling the expression of virulence factors by gut bacteria has major implications for pathogenesis.

In trying to understand why some people do not excrete CH4 in their breath, it was shown (with Gibson) that many humans carry sulphate reducing bacteria (SRB), which compete with methanogenic archae for H2 from fermentation. Quantitative studies of H2 and CH4 excretion (with Christl and Murgatroyd), using the Dunn's human calorimeters, showed that a number of pathways for H2 metabolism exist in the colon, each of which has different implications for health. In studies of patients with Pneumatosis Cystoides Intestinalis we showed that all the major pathways of hydrogen disposal were defective, thus making this disease the first disorder of hydrogen disposal to be described. Of the various pathways of hydrogen metabolism in the human colon the production of sulphide from sulphate by SRB is considered to be the most harmful. In healthy subjects and patients with ulcerative colitis (with Pitcher), we went on to show that some had "active" SRB, which responded to sulphate feeding by increasing sulphide production. In ulcerative colitis the potentially damaging effects on the mucosa may be ameliorated by the drug 5-ASA, which inhibits sulphide production by the colonic microbiota in vitro. The role of sulphide in the large bowel maybe important both for inflammatory bowel disease and for genotoxic events in the epithelium. More recent studies in Dundee showed a clear effect of both s-amino acids and of inorganic sulphur on the generation of reduced sulphur compounds in the large bowel, and were funded by MAFF/FSA because of the use of S additives in food.

By 1990 the possibility to control bacterial activity in the human colon by diet became a major interest. In addition to the general effect that carbohydrate has on biomass production, it is now clear that specific components of the diet may selectively stimulate growth of particular species of bacteria. In addition to the work with SRB we showed (with Gibson) that fructooligosaccharides selectively stimulate bifidobacterial growth. This has contributed to the concept of prebiotic foods (developed in collaboration with Roberfroid in Brussels). The food industry is currently marketing many such foods and idea of “functional foods” that benefit health over and above their normal macronutrient content, is one of the most important in nutrition for many years.

The most serious disease of the large intestine is colo-rectal cancer (CRC). In an extended series of investigations over 20 years with Bingham, involving epidemiology, human physiological and cellular studies, we highlighted the importance of dietary fibre and RS in protecting against CRC and postulated a mechanistic hypothesis based on fermentation and the protective effects of butyrate on the colonic epithelium. Early work (with Drasar and Hill) looked at the role of bile acids as mediators of the risk for CRC seen in epidemiological studies of dietary fat. Subsequent studies (with Eastwood and Heaton) showed the importance of the relationship between bowel habit and risk of CRC. More recently (with O'Neill and Loktionov) we demonstrated the importance of meat protein as a source of N-nitroso compounds (N-NOC) in the colon, and developed a new technique which isolates epithelial cells from faeces using immunomagnetic beads, to relate N-NOC production to DNA damage at key sites of genes known to be associated with CRC risk. The results of this work were influential in deciding the recommendations for meat intake in the UK in the recent DH Diet. Subsequent work by Bingham showed that it was the haem component of red meat that stimulated the endogenous production of N-nitroso compounds in the large bowel.

With the transfer of the nucleus of the Gut Group to Dundee in 1999, the focus of our studies became the Interaction of microflora, diet and the gut epithelium and its consequences for health. This work is now led by Professor George Macfarlane. We are particularly interested in events that occur at the epithelial surface of the large bowel between the flora, diet, cellular metabolism and immune function. The group is currently exploring the development of bacterial biofilms in the colon using new chemotaxonomic and molecular probe techniques in healthy people, in vitro models and in inflammatory bowel disease. We have examined the role of diet in modulating the gut flora and especially the possibility that specific substrates will have a selective effect on their composition and metabolism. This resulted in the early studies of prebiotics, first published in 1995, has led us into an extensive programme of work on pro, pre and synbiotics. The work on dietary carbohydrates is now ready to be applied to population studies and will give for the first time an appraisal of the role of the different carbohydrate fractions of the diet in disease. This is being done through consultancy with WHO.

Group alumni

Key members of the Gut Group, photographed outside the MRC Dunn Clinical Nutrition Centre in 1990. George Macfarlane and John Cummings moved to Dundee in 1999. Glen Gibson is now Professor of Food Microbial Sciences and Head of FMSU Research Group, at Reading University, Hans Englyst is Director and owner of Englyst Carbohydrate Services in Southampton and Sheila Bingham became Director of the Medical Research Council Centre for Nutrition and Cancer Survival and Prevention in the University of Cambridge in 2005.

Lectures and conferences

Member of the Nutritional Guidelines Advisory Group (NUGAG) on Diet and Health of WHO.

Recent meetings in Hangzhou (March 2013) and Copenhagen (October 2013).