**2. Early histological backgrounds of "scientifically approach to nutrition"**

For more than 200 years, the fibre in plant foods has been known by animal nutritionists to have significant effects on digestion. Its role in human nutrition began to be investigated towards the end of the nineteenth century. Denis Burkitt (1911–1993), a surgeon, brought back to the United Kingdom from Africa ideas from a range of disciplines along with his own observations to propose a radical view of fibre in human health. Later, Burkitt met with three physicians in London, Cleave, Campbell, and Trowell, who collected observations on fibre consumption and the distribution of different diseases in Africa. Trowell worked in London at St. Thomas' Hospital and had visited Uganda in 1948, 1958, and 1970, and Kenya in 1929. He observed that the distribution of different diseases changed along with changes in the population during the observed periods. Namely, the numbers of different diseases increased in people who came from Western countries, whereas the numbers remained unchanged in the African populations. In addition, he noted the emergence of entirely new diseases like diabetes mellitus, hypertension, and malignant conditions in the population coming from Europe.

Burkitt built on the work of Cleave, Campbell, and Trowell to develop the "fibre hypothesis" [2, 3], the main point of which is that fibre consumption decreases the risks of obesity, diabetes, dental caries, various vascular disorders, large bowel cancer, appendicitis, and diverticulosis, particularly in the UK population. This hypothesis was considered groundbreaking at the time, and spurred further research (e.g., "Dietary Fibre in Europe. Current State of Knowledge on Definitions, Sources, Recommendations, Intakes and Relationships to Health." Nutrition Research Reviews. 2017;**30**:149-190).
