John Fleming Brock was educated at Grey School, Port Elizabeth. In 1925 he entered the Honours School of Physiology at Oxford on a Rhodes Scholarship, after completing his undergraduate degree at the University of Cape Town. He completed his M.A. in 1931 and became a member of the Royal College of Surgeons in 1932. Also in 1932 he was awarded the Leverhulme Research Scholarship and spent one year at Boston City Hospital and one year at the London Hospital researching 'iron deficiency in relation to hypochromic anaemia'.
In 1938 he was appointed Professor of Medicine at the University of Cape Town, where he remained until his retirement in 1970. In 1970 he became Honorary Professor of the History and Philosophy of Medicine.
He was well-known for his research into nutritional diseases, especially kwashiorkor, and was nutrition consultant to the World Health Organisation for 20 years. He served as president of the South Africa College of Physicians, Surgeons and Gynaecologists for a term in the 1960s and also on the U.C.T. Council for 22 years, where he showed himself to be a champion of academic freedom.
He pioneered medical research at the University of Cape Town Medical School in the 1950s when emphasis on post-graduate research began to outweigh undergraduate teaching. His publications include
'Human Nutrition and Dietetics' - S Davidson, R Passmore and J F Brock 1972
'The Findings of the Cape Nutrition Survey' 1942
'Kwashiorkor in Africa' Special Report Series No 8. M Autret and J F Brock 1950
'Significant Trends in Medical Research'. Churchill, London 1959 p.243
'Squibb Centennial Lectures' - Pitman, New York 1959 p.41
'Humanity and subsistence' 1961
'Recent Advances in Human Nutrition' Churchill, London 1961
'Highlights of Medical Research' 1977