Edward Mellanby used the experimental method to investigate medical problems. In 1918, working at King's College for Women, London, he provided conclusive evidence that rickets is a dietary deficiency disease due to lack of a fat-soluble vitamin [D]. In Sheffield he demonstrated that cereals, in an unbalanced diet, produced rickets due to the phytic acid content reducing the availability of calcium. Mellanby became Secretary of the Medical Research Council (1933–49) but continued his research by working at weekends. In the 1930s he campaigned for the results of nutritional research to be used for the benefit of public health. During World War II he acted as a scientific adviser to the War Cabinet and had a strong influence on the food policy which maintained successfully the nutrition of the population during the shipping blockade. Mellanby was a formidable person but with sagacity he promoted new research and guided the expansion of the organization.