Nutrition Research

Publication Analysis 2007-2013
by Kathleen Gransalke, Labtimes 03/2016

View the Tables: Europe...and the World, Most Cited Authors...and Papers

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Photo: Pixabay/Pashminu

The Europe-wide cohort study, EPIC, exploring the link between nutrition and cancer, determines the “winners and losers” of the most-cited nations’ and authors’ ranking.

Burger with fries or ember bed-roasted veal wrapped in mushrooms with celeriac and apple, roasted celeriac jus and potato pithiviers (main dish at last year’s Nobel Banquet)? What would you like to have now? Fact is, not everything we eat is good for us. Already, back in ancient Greece, Aristotle and Hippocrates noticed a link between diet and health/disease. “Persons in good health quickly lose their strength by taking purgative medicines, or using bad food,” Hippocrates wrote more than 2,000 years ago. He also realised that “when more food than is proper has been taken, it occasions disease (…)”.

The latter observation is today more topical than ever. Termed the global obesity epidemic or globesity, numbers of overweight or obese people have doubled throughout the last 30 years. According to the WHO, in 2014, almost two billion adults were overweight; of these, 600 million were obese. It’s up to nutrition researchers to analyse these trends and associated health risks. But herein also lays nutrition researchers’ big responsibility, as it is exactly those findings that shape governmental dietary guidelines and thus, have a direct impact on the public.

High and low impact

Now, without further ado, let’s have a closer look at the scientific output of nutrition researchers in Europe between 2007 and 2013. For our nations’ ranking, we, once again, relied on the specialist journals, as listed by the Web of Science database, under the subject category Nutrition & Dietetics. Interestingly, for a discipline with such a large impact, only a handful of specialist journals have an impact factor above 6. In contrast to the nations’ ranking, the most-cited authors’ ranking is, again, based on articles, reviews and proceedings papers published in all journals, multi- as well as monodisciplinary ones.

Sticking to food terminology, we will now serve the starters of this publication analysis, the nations’ ranking. Famous for fish and chips, shepherd’s pie and mint sauce, England is the unchallenged number one in European nutrition research. Then there are some surprises. Places two and three are occupied by Spanish and Italian researchers. Although this isn’t so surprising these days. Among the European diets, the Mediterranean diet, with lots of olive oil, herbs and spices, has been shown to be associated with many health benefits and is thus at the centre of many public health studies. This study focus could also explain Greece’s top position (12th).

Other nations can’t quite keep up with that performance. Despite their world-famous “Schnitzel culture”, Germany (5th) and Austria (19th) did not do very well in nutrition research. Sorted by citations per article, Scotland (24.4), The Netherlands (23.1) and Finland (22.9) are at the top. When compared to their US-American peers, European nutrition researchers again had a higher output and more citations but the citation-per-article ratio is, once more, in favour of US nutrition researchers.

After having digested the nations’ performance starters, it’s time for the main dish, the most-cited papers of nutrition researchers. Here, we decided to omit those papers that merely describe certain gene variants predisposing to diabetes or adiposity. The same limitation applies to the most-cited authors’ ranking, in which scientists who mainly publish susceptibility studies have been excluded.

This puts two papers from the labs of Patrice Cani and Remy Burcelin in the top five (at positions 1 and 3). Both are about metabolic endotoxemia as a cause of obesity, diabetes and insulin resistance. The scientists noted, in mice, that a four-week high-fat diet chronically increased the plasma levels of lipopolysaccharide, an inflammatory reagent, from gut bacteria, two to three fold. “Metabolic endotoxemia dysregulates the inflammatory tone and triggers body weight gain and diabetes,” Cani et al. discovered. Top papers on spots two and five also have something in common: both explore the relationship between adiposity/obesity and mortality. In Whitlock et al., the researchers found that the median survival of persons with a body mass index (BMI) between 30-35 kg/m2 (moderately obese) is reduced by two to four years; of persons with a BMI between 40-45 kg/m2 (very severely obese) by eight to ten years. And last but not least, in 4th place, there’s a single-author review about glucagon-like peptide 1 by its discoverer, Jens Juul Holst. This neuropeptide and gut hormone is released when we eat food; it stimulates insulin and inhibits glucagon secretion.

A true EPIC study

Ready for the delicious dessert? Panna cotta, crema catalana or Schwarzwälder Kirschtorte? European cuisine is versatile; the topics of the nutrition researchers in our top 30 most-cited authors’ list are not. Almost all are epidemiology studies, trying to understand how certain foods and eating habits make us sick. A big portion of those publications present the results of the European Prospective Investigation into Cancer and Nutrition (EPIC) study. With more than half a million participants, it is one of the largest cohort studies in the world. Data collection began in 1993 in Spain, France, Italy and the United Kingdom; today, the EPIC biorepositories host more than nine million aliquots of plasma, serum, leukocytes and erythrocytes.

Intriguingly, not less than 15 most-cited nutrition researchers in our top 30 currently are Principal Investigators at local EPIC centres: Anne Tjønneland, 5th; Kim Overvad, 7th (Denmark); Françoise Clavel-Chapelon, 11th (France); Heiner Boeing, 4th; Rudolf Kaaks, 12th (Germany); Antonia Trichopoulou, 19th (Greece), Domenico Palli, 23rd; Salvatore Panico, 29th; Rosario Tumino, 20th (Italy); Göran Hallmans, 9th (Sweden); H. Bas Bueno-de-Mesquita, 13th; Petra Peeters, 15th (The Netherlands); Timothy Key, 22nd (Oxford) and our top duo Kay-Tee Khaw, 2nd and Nicholas Wareham, 1st (Norfolk). Add to this the study’s coordinator, Elio Riboli (6th), and a few former (Jakob Linseisen, 26th) as well as deceased investigators (Sheila Bingham, 8th; Dimitrios Trichopoulos, 24th) and our top 30 list is almost complete.

Nutrition researchers number one and two, Nicholas Wareham and Kay-Tee Khaw, stand out not only with the high number of citations but also with the high number of publications – more than 500 for each one of them. This translates to publishing roughly two papers per week. In epidemiology, collaborative papers with hundreds of authors are rather the norm and not the exception. But can really everyone call him/herself an author of that study? “Not many of these individuals will have even seen the paper, and so the term ‘author’ seems meaningless and ‘contributor’ more appropriate,” says COPE, the Committee on Publication Ethics. As Web of Science can’t yet separate authors from contributors, we might take this ranking with a pinch of salt or rename it “most-cited authors/contributors in nutrition research”.

Besides the epic EPIC study, more nutrition research has been going on in Europe. In France, Serge Hercberg (25th) and ­Pilar Galan (30th) worked on the SU.VI.MAX project, exploring the health effects of antioxidant vitamins and minerals, and the ­Nutrinet-Santé study: “a web-based prospective study on the relationship between nutrition and health and determinants of dietary patterns and nutritional status”.

Also, the above-mentioned top paper authors, Jens Juul Holst (16th) and Patrice Cani (28th), made our top 30. Focussing on physiological aspects of food metabolism are Stephen O’Rahilly (17th) and Johan Auwerx (18th). The former is interested in elucidating the processes controlling energy intake and expenditure to get to grips with aetiology and pathophysiology of human metabolic and endocrine diseases. Auwerx wants to understand “how diet, exercise and hormones control metabolism”. Last but not least, Michael Stumvoll (21st) focusses on genetics of adipositas, diabetes but also neuroendocrine control of appetite and the benefits of a Mediterranean diet on cognitive function in aging.

Personalised dietary advice

For now, nutrition research is predominated by large scale cohort studies, analysing effects of diet on health, on population level. The future of the discipline, however, might get a little more personal – personalised nutrition is the name of the game. Nutrigenetics and -genomics will help researchers decipher how one’s own genetic makeup affects food metabolism and, vice versa, how nutrients affect gene expression. In a 2011 review, Australian nutrition researchers assert: “At the moment, there is a degree of public confusion and an immunity to messages that foster unpopular advice, such as ‘get more exercise’ or ‘eat less calories’. Nevertheless, in the long term, these fields of endeavour may be the only way to optimise nutrition for optimal effects on health, wellness, and a slowing of the deterioration associated with the aging process” (J Nutrigenet Nutrigenomics, 4(2): 69–89).

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Last Changed: 21.06.2016

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