In the 1920s under Boyd Orr’s leadership, the Rowett Institute did some important and pioneering work with its "milk in schools" experiment – which led subsequently to legislation in Scotland to provide milk for school children, an initiative later followed by the rest of the UK.
In a major study, Food Health and Income, published in 1936 Boyd Orr and his colleagues classified the UK population into six groups according to income, then estimated the adequacy of the diet consumed by each of the groups. The study established that more than a third of the population (the poorest third) did not enjoy a diet that was up to the "health standard", with the main reason being their inadequate purchasing power.
The Carnegie Trustees, driven by their concern for the "improvement of the well-being of the masses" became keenly interested in Boyd Orr’s work and concluded that a further and more extensive inquiry would be valuable, funding the Rowett team to the sum of £15,000 to look deeper.
Between 1937 and 1939, a more detailed study was carried out of thirteen hundred families throughout England and Scotland, involving nearly 8,000 people in 16 locations. This was hailed as the "largest empirical inquiry hitherto attempted in Britain into the relationship between health and diet."
The work had only just been completed when the Second World War broke out.
All was not lost however. Evidence from the Rowett Carnegie Survey was key to the development of a progressive and effective food policy for Britain at war, based on the nutritional needs of different groups. Lord Woolton, the wartime Minister of Food, subsequently pointed out that the Rowett Carnegie Survey’s evidence on food consumption at different income levels was of great importance in evolving wartime food policy. Boyd Orr himself observed that "in spite of the acute food shortages, the women and children of the poorer classes were healthier at the end of the war than at the beginning of it."
Boyd Orr was a key figure in the "nutrition campaign" which transformed attitudes and aspired to bring a diet adequate for health within the reach of the poorest. Academics from various disciplines worked alongside politicians and administrators to inform public opinion, to support rationing and to influence the Ministry of Food.
Boyd Orr recalled graphically that:
"The result of this movement was seen during the war when a well informed public opinion approved and helped to get carried into effect a rationing system which gave priority for milk and eggs to mothers and children and ensured that when a cargo of oranges came in, a millionaire could not get one until the poorest child in the slums had got sufficient for its needs."
In the end the Rowett Carnegie Survey was published in 1955 as Family Diet and Health in Pre-War Britain. It was both an historical record of the state of nutrition at the start of the war and a key influence in driving future policy. In 1955 the relationships between food and health "and the social evils which lead to poor nutrition" were still of fundamental importance. The authors of the Survey pointed out that "Food habits in this country have undergone a revolution since the Survey was made". They sounded a note of caution however, concerned that the end of food rationing might mean that "income will again become one of the chief determinants of levels of nutrition."
Boyd Orr retired from the Rowett Institute at the end of the war but he remained very active, campaigning for world peace and taking up office as the first Director of the Food and Agriculture Organisation. He was awarded the Nobel Peace Prize in 1949 and in the same year was elevated to the peerage as Baron Boyd Orr of Brechin.