Seven Country Study

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The seven-country study was the first multicenter epidemiological study worldwide to investigate risk factors for premature mortality and cardiovascular disease . The initiator of the study was the American scientist Ancel Keys .

background

In the early 1950s, Keys learned from a conversation with an Italian colleague that there was hardly any heart disease in his home country. Keys then went to Naples with his wife , set up a laboratory and began research. He quickly found that residents had less heart disease than the United States and had very low serum cholesterol levels. A first observational study in Minnesota , started in 1947, tracked male workers for 15 years.

State data collections from other countries also showed a further statistical correlation: the higher the intake of total dietary fat, the higher the mortality from heart disease (so-called "six countries study").

Keys and his wife confirmed this connection on further trips and Keys concluded from the data that dietary fat and thus higher cholesterol levels contribute to the increase in coronary artery disease . In 1955 Keys presented his ideas to other researchers in the international environment of the World Health Organization , where little faith was given to his theory. Then he designed the "Seven Countries Study".

execution

From 1958 on, Keys began epidemiological surveys in seven countries over a period of 6 years . The study was conducted on 12,763 healthy middle-aged men in Italy, the Greek islands of Corfu and Crete , Yugoslavia , the Netherlands , Finland , Japan, and the United States . The locations and participants were not chosen at random. Except for the centers in Minnesota, Rome and Belgrade , all cohorts were rural.

When choosing the centers, Keys limited himself to countries that were able to provide reliable data a decade after the end of World War II . France was intended to participate, but turned down the invitation. Central Europe was still too badly affected by the World War, and the food supply was still insufficient.

The subjects were asked about various lifestyle factors (physical activity, smoking , diet), the diet was recorded with food diaries and, for example, by analyzing food samples. All participants were physically examined; the evaluation of certain data from all centers was only carried out at the location in the USA for the sake of standardization. All surveys were repeated at 5-year intervals, but there were different schemes for each cohort to determine whether intervals were omitted. Individual centers developed follow-up studies that included more frequent intervals or additional tests.

Results

The results of the study were published in book form in 1966, 1970 and 1980.

The study showed a strong influence of age, smoking, and blood pressure on all-cause mortality. In most of the centers, body weight played no statistical role; in southern Europe, even a low body weight appeared to be more advantageous. The regional differences in total mortality were mainly explained by blood pressure.

The cardiovascular morbidity and mortality was especially with high blood pressure and higher cholesterol levels in context, but also the age and smoking contributed to the risk. Body weight and physical activity were of little importance. Keys also showed a strong correlation between saturated fat intake and cardiovascular disease as well as their mortality. There was also a statistical relationship with sugar consumption, but it was much less pronounced. After statistical correction, only the effect on saturated fat remained.

The traditional Mediterranean diet was recognized as a clearly healthy diet.

Later analyzes showed that cardiovascular risk factors also contribute to dementia .

criticism

Keys received an objection as early as the 1960s. Thomas Cleave blamed processed carbohydrates as a causative factor of cardiovascular risk. A little later, John Yudkin specified that high sugar consumption was the real problem. Keys sharply denied these assumptions, citing lack of data, alleging that Yudkin had a conflict of interest with the food industry.

As a prospective observational study, the seven-country study naturally cannot assess causality . Nevertheless, the interpretation of the study mostly made a direct recommendation to reduce dietary fat. Supporters of the "fat hypothesis" from other research groups received extensive grants from the food industry and published studies that replicated Keys' data. Many of these researchers have received influential posts in the US health service, in part through the advocacy of Keys. These conflicts of interest also directly and indirectly affect the interpretation of the results of Keys' work, even though he himself did not receive any support from the food industry.

The selection of the countries examined is also viewed critically. Some critics, including the US nutritionist Robert Lustig , accused Key of premeditation, claiming that he knowingly failed to study countries because they failed to support his hypotheses or because they misappropriated data he collected. According to Udo Pollmer , the seven-country study can now be viewed as “a large-scale fraud”. The historical circumstances of the study planning , interpretation and publication were extensively reviewed by Nina Teicholz in 2016 . Journalist Gary Taubes has also been critical of the study and its consequences in articles and books since 2001.

The allegations made are decidedly refuted in a white paper from 2017: The "Six Countries Study" incriminated by Jacob Yerushalmy and Herman Hilleboe was not a study by Keys, but an evaluation of government data from six countries. A data collection from 22 countries, which is compared to his seven-country study, comes from an older study from 1953 in which countries were actually examined, but whose initial data were of inferior quality. Critics explained: if you include all countries in the comparison, there is no positive correlation between the proportion of animal fats in the diet and the incidence of heart disease. In fact, Keys limited himself to seven of these countries, collecting data from people for his study and observing their individual diet, health and cause of death for over 30 years. The correlation of all 22 countries is weaker, but still there. The authors of the white paper therefore clearly reject the allegations of scientific fraud, but do not question numerous limitations.

consequences

From 1980, with the publication of the 25-year data, the professional societies in the USA, the United Kingdom and other countries recommended that dietary fat be significantly reduced. Although the seven-country study only showed damage from saturated fats, the recommended diet applied to all fat. A clear emphasis on the benefits of the Mediterranean diet - low in saturated fats, high in unsaturated fats - did not emerge until decades later.

Since the 1980s, efforts have also been made to lower the cholesterol level of risk patients.

In order to provide the scientific evidence for women as well - the seven-country study was only carried out on men and other studies, such as the Nurses' Health Study , were not representative enough or did not show the same effects - a new large observational study was specifically made in 1993 female participants: the Women's Health Initiative Study . Surprisingly, it showed no advantage for "low-fat".

Today's scientific classification of the results

The increased incidence of heart disease in the western world in the 20th century can also be explained by other factors, such as increased sugar and white bread consumption and a lack of exercise . Meta-analyzes from 2019 do not see any statistical association between the intake of saturated fat and cardiovascular diseases or mortality in observational studies.

The influence of smoking, age and cholesterol levels are still undisputed.

The lack of association between body weight and mortality has now been extensively researched as an obesity paradox .

Despite the decades of misinterpretation of the study - not all fat is bad, only saturated fat - the seven-country study is considered to be one of the first proofs of the superiority of the Mediterranean diet . It is also of particular historical importance because at the time of the study the differences in dietary patterns between the countries were much more pronounced than they are today.

Individual evidence

  1. ↑ a b Biographical notes on Ancel Keys and Salim Yusuf: Origins and significance of the Seven Countries Study and the INTERHEART Study.
  2. ↑ Ancel Keys: Human Atherosclerosis and the Diet . In: Circulation . tape 5 , no. 1 , 1952, pp. 115-118 , doi : 10.1161 / 01.CIR.5.1.115 (English).
  3. ^ Keys Ancel, Taylor Henry Longstreet, Blackburn Henry, Brozek Josef, Anderson Joseph T .: Coronary Heart Disease among Minnesota Business and Professional Men Followed Fifteen Years . In: Circulation . tape 28 , no. 3 , September 1, 1963, pp. 381-395 , doi : 10.1161 / 01.CIR.28.3.381 .
  4. ↑ J. Yerushalmy, HE Hilleboe: Fat in the diet and mortality from heart disease; a methodologic note . In: New York State Journal of Medicine . tape 57 , no. 14 , July 15, 1957, ISSN  0028-7628 , p. 2343-2354 , PMID 13441073 .
  5. ↑ The Seven Countries Study - The first epidemiological nutrition study, since 1958. Retrieved May 7, 2020 (American English).
  6. ↑ a b c Ancel Keys 7 Countries Study: Still accurate, actionable and relevant
  7. ↑ The Seven Countries Study - The first epidemiological nutrition study, since 1958. Retrieved May 7, 2020 (American English).
  8. ^ Keys, Ancel, 1904-2004 .: Seven countries: a multivariate analysis of death and coronary heart disease . Harvard University Press, Cambridge, Mass. 1980, ISBN 0-674-80237-3 .
  9. ↑ The Seven Countries Study -Cross-cultural correlations. In: Seven Countries Study | The first study to relate diet with cardiovascular disease. Retrieved May 7, 2020 (American English).
  10. ↑ The Seven Countries Study -Cross-cultural correlations. In: Seven Countries Study | The first study to relate diet with cardiovascular disease. Retrieved May 7, 2020 (American English).
  11. ^ Avoxa media group Deutscher Apotheker GmbH: Benefits and scientific principles. Retrieved May 8, 2020 .
  12. ↑ Alonso A, Jacobs Dr, Menotti A, Nissinen A, Dontas A: Cardiovascular Risk Factors and Dementia Mortality: 40 Years of Follow-Up in the Seven Countries Study. May 15, 2009, accessed May 7, 2020 .
  13. ↑ Ancel Keys 7 Countries Study: Still accurate, actionable and relevant. In: True Health Initiative. Retrieved May 7, 2020 (American English).
  14. ↑ A. Keys: Sucrose in the diet and coronary heart disease . In: Atherosclerosis . tape 14 , no. 2 , September 1, 1971, ISSN  0021-9150 , p. 193-202 , doi : 10.1016 / 0021-9150 (71) 90049-9 , PMID 4940760 .
  15. ↑ Keys A: Coronary Heart Disease - The Global Picture. September 1975, accessed May 7, 2020 .
  16. ^ Deutscher Ärzteverlag GmbH, editorial office of the Deutsches Ärzteblatt: How the US sugar industry blamed fats. September 12, 2016, accessed May 8, 2020 .
  17. ↑ Anahad O'Connor: How the Sugar Industry Shifted Blame to Fat . In: The New York Times . September 12, 2016, ISSN  0362-4331 ( online [accessed May 7, 2020]).
  18. ↑ FOCUS Online: 55 years ago, the sugar industry bribed researchers, we can still feel the consequence today. Retrieved May 7, 2020 .
  19. ↑ Richard Friebe: Low-Fat-Diet: A single fat lie . In: FAZ.NET . ISSN  0174-4909 ( Online [accessed May 7, 2020]).
  20. ↑ Rethinking - Bitter Realization. Retrieved May 8, 2020 .
  21. Jump up ↑ University of California Television (UCTV): Sugar: The Bitter Truth on YouTube , July 13, 2009, accessed May 20, 2020.
  22. ↑ Udo Pollmer : Study on Heart Attack Risk - Is Cholesterol Harming? Invented everything! In: Deutschlandfunk Kultur . ( deutschlandfunkkultur.de [accessed on July 23, 2017]).
  23. ↑ Rethinking - Bitter Realization. Retrieved May 8, 2020 .
  24. ^ Editor: Fat and politics - Nina Teicholz on how the Seven Countries Study influenced dietary policy. In: Diabetes. Retrieved May 8, 2020 (UK English).
  25. ^ G. Taubes: Nutrition. The soft science of dietary fat . In: Science (New York, NY) . tape 291 , no. 5513 , March 30, 2001, ISSN  0036-8075 , p. 2536-2545 , doi : 10.1126 / science.291.5513.2536 , PMID 11286266 .
  26. ^ Gary Taubes: Good calories, bad calories .
  27. ↑ J. Yerushalmy, HE Hilleboe: Fat in the diet and mortality from heart disease; a methodologic note . In: New York State Journal of Medicine . tape 57 , no. 14 , July 15, 1957, ISSN  0028-7628 , p. 2343-2354 , PMID 13441073 .
  28. ↑ Nutritionist Ancel Keys, once the pride of UMN research, presents a fat problem for modern science. Retrieved May 7, 2020 .
  29. ↑ Dr Joel Kahn: The Posthumous Assassination of Dr. Ancel Keys. In: Dr. Joel Kahn. December 19, 2016, accessed May 7, 2020 (American English).
  30. ^ Ross L. Prentice, Lianne Sheppard: Dietary fat and cancer: consistency of the epidemiologic data, and disease prevention that may follow from a practical reduction in fat consumption . In: Cancer Causes and Control . tape 1 , no. 1 , July 1990, ISSN  0957-5243 , pp. 81-97 , doi : 10.1007 / bf00053187 .
  31. ^ Avoxa media group Deutscher Apotheker GmbH: Benefits and scientific principles. Retrieved May 8, 2020 .
  32. ↑ Rethinking - Bitter Realization. Retrieved May 8, 2020 .
  33. ↑ Manuela Neuenschwander, Aurélie Ballon, Katharina S. Weber, Teresa Norat, Dagfinn Aune: Role of diet in type 2 diabetes incidence: umbrella review of meta-analyzes of prospective observational studies . In: BMJ (Clinical research ed.) . tape 366 , July 3, 2019, ISSN  1756-1833 , p. l2368 , doi : 10.1136 / bmj.l2368 , PMID 31270064 , PMC 6607211 (free full text).
  34. ↑ Daan Kromhout: Serum Cholesterol and Coronary Heart Disease in the Seven Countries Study . In: Developments in Cardiovascular Medicine . Springer US, Boston, MA 2002, ISBN 978-1-4613-5402-4 , pp. 127-143 .
  35. ^ Avoxa media group Deutscher Apotheker GmbH: Benefits and scientific principles. Retrieved May 8, 2020 .
  36. ↑ Julia Rudorf: The world at one table. In: The time . December 4, 2012, accessed May 8, 2020 .