Thomas Latimer Cleave, known as 'Peter' to his friends and colleagues, was born in Exeter in 1906, and educated at Clifton College. Between 1922-27, he attended medical schools at the Royal Infirmary, Bristol, and St Mary's Hospital, London, achieving MRCS and LRCP. At Bristol, one of his teachers was Rendle Short, who had proposed that appendicitis is caused by a lack of cellulose in the diet. (It is worth noting, perhaps, from a biographical perspective, that Cleave's sister had died at the age of eight years from a perforated appendicitis). Charles Darwin's writings provided the intellectual framework to Cleave's life-long engagement with the relationship between diet and health, built upon the premise that the human body is ill-adapted to the diet of modern (western) man. In this context, Cleave considered refined carbohydrates (white flour and sugar) to be the most transformed food, and therefore the most harmful.
After completing his medical training, Cleave entered the Royal Navy in 1927 as Surgeon Lieutenant. Between 1938-1940, he served as Medical Specialist at RN Hospital, Hong Kong. It was during his war service, in 1941, whilst on the battleship King George V, that he acquired his Naval nickname - "the bran man" - when he had sacks of bran brought on board to combat the common occurrence of constipation amongst sailors. Following war service, he worked at Royal Naval Hospitals in Chatham (1945-1948), Malta (1949-1951) and Plymouth (1952-1953). He retired from the Royal Navy in 1962 as Surgeon Captain, having finished his naval career as Director of Medical Research at the RN Medical School.
Although Cleave had published a short booklet, A Molecular Conception of Organisms and Neoplasms (1932), the publication to first receive attention from his peers was "The neglect of natural principles in current medical practice," Journal of the Royal Naval Medical Service, 42:2 (1956), 55-63. This paper can be considered the foundation to a series of incremental publications aligning (Darwinian) 'natural principles' in diet to sustained good health. Major subsequent publications were: Fat Consumption and Coronary Heart Disease (1957), On the Causation of Varicose Veins (1960), Peptic Ulcer (1962) and Diabetes, Coronary Thrombosis and the Saccharine Disease (1966). His final publications were The Saccharine Disease (1974), which largely synthesised his previous publications, and "Over-consumption. Now the most dangerous cause of disease in Westernised countries," Public Health: The Journal of the Society of Community Medicine, 91:3 (1977), 127-31.
Recognition came late to Cleave. In 1979, he was awarded both the Harben Gold Medal of the Royal Institute of Public Health and Hygiene and the Gilbert Blane Medal for Naval Medicine by the Royal College of Physicians and Surgeons. During the 1970s, his ideas found favour in America, where the doctor and author Miles H Robinson was a particular champion. Robinson was instrumental in the American publication of The Saccharine Disease, for which he wrote an introduction. In 1973, Cleave gave evidence to the US Select Committee on Nutrition and Human Needs, at the invitation of Senator George McGovern.
Not entirely without intellectual support (Sir Richard Doll provided a Foreword to successive editions of Diabetes, Coronary Thrombosis and the Saccharine Disease), Cleave nevertheless remained very much an outsider to the medical establishment throughout his life, although the importance of fibre in food was eventually to gain considerable popular support and the general support of the medical establishment. His publications (largely produced at his own expense) were often criticised for being too theoretical and insufficiently grounded in detailed primary research. As Kenneth Heaton has noted, he was "recording differences in disease patterns over time and space long before the epidemiology of chronic diseases was a recognised discipline … [and] he painted with broad strokes on the biggest possible canvas when others were focusing on ever more minute areas of investigation."