Ida Smedley MacLean (1877–1944) was a pioneering English biochemist whose research on fatty acids and lipid metabolism helped lay foundations for modern understanding of essential fats, while her persistent advocacy opened professional doors for women in British chemistry and university life.
Born Ida Smedley on 14 June 1877 in Birmingham, she grew up in a prosperous, cultured, and progressive household. Her father, William T. Smedley, was a businessman; her mother, Annie Elizabeth Duckworth, came from a Liverpool merchant family and taught her daughters at home until the age of nine. The family valued education, debate, music, languages, and independent thought. Ida’s older sister, Constance Smedley (1876–1941), became a writer, playwright, and founder of the International Association of Lyceum Clubs for professional women. Their upbringing emphasized intellectual curiosity rather than conventional limits on girls.
Ida attended King Edward VI High School for Girls in Birmingham from 1886 to 1896. She won a scholarship to Newnham College, Cambridge, where she studied from 1896 to 1899. In the Natural Sciences Tripos she earned a first class in Part I and a second class in Part II, focusing on chemistry and physiology. Cambridge did not yet award degrees to women, so she later received her Doctor of Science (D.Sc.) from the University of London in 1905. After a period holding a Bathurst scholarship, she conducted postgraduate research at the Central Technical College in London (later part of Imperial College) and the Davy-Faraday Research Laboratory at the Royal Institution, working under the organic chemist Henry Edward Armstrong. Her early papers examined the cause of colour in dinitrobenzenes and the optical properties of compounds containing conjugated double bonds, including studies of diphenylbutadienes and hexatrienes published in the Journal of the Chemical Society in 1908.
In 1906 she became assistant lecturer and demonstrator in the chemistry department at the University of Manchester (Victoria University), the first woman on its staff. She taught there until 1910, working in the women’s laboratories and continuing research on the optical properties of organic compounds. In 1910 she received one of the first Beit Memorial Fellowships and moved to the Lister Institute of Preventive Medicine in London. There she shifted toward biochemistry under Arthur Harden, joining a laboratory that combined pathological chemistry and chemical research. Around this time she developed a lifelong interest in fat metabolism, a relatively neglected field then being explored by J. B. Leathes and others at the Institute. She received the Ellen Richards Prize from the American Association of University Women for her research.
On 28 March 1913 she married Hugh MacLean, a fellow researcher at the Lister Institute who later became professor of medicine at St Thomas’ Hospital and an authority on phospholipids. They had two children: a son, Kenneth Smedley MacLean (1914–2009), who became a distinguished physician and director of medicine at Guy’s Hospital, and a daughter, Barbara. Marriage and motherhood did not end her scientific career, though opportunities were constrained. In 1914 she was invited to apply for a chair in biochemistry at the University of London, but the committee withdrew consideration upon learning she was pregnant. During the First World War she contributed to Admiralty work, including large-scale acetone production by fermentation of starch—a project associated with Chaim Weizmann that proved industrially important.
Her most significant scientific contributions concerned the structure, origin, and function of fatty acids. In 1912 she published a systematic re-examination of the fatty acids in butter, showing they consisted of straight-chain acids with even numbers of carbon atoms and that unsaturated acids were present beyond the well-known oleic acid. The following year she proposed a biosynthetic pathway: pyruvic acid from carbohydrate breakdown could lose carbon dioxide to form a two-carbon fragment (“active acetaldehyde”) that could be used to build longer chains through condensation, dehydration, and reduction. This insight anticipated later confirmation that the two-carbon unit is acetyl-coenzyme A. She also studied fat synthesis and metabolism in yeast, helping to clarify connections among fats, carbohydrates, and proteins.
Later work focused on polyunsaturated fatty acids and their essential roles. Collaborating with Leslie C. A. Nunn and others, she investigated fat-deficiency disease in rats and the conversion of linoleic acid into arachidonic acid. In 1940 she and Nunn published studies on the effects of methyl arachidonate and linoleate. Using alkaline permanganate oxidation rather than ozonolysis, she identified degradation products that established the structure of arachidonic acid as 5,8,11,14-eicosatetraenoic acid—the first correct complete assignment of its double-bond positions. This work supported the emerging concept that linoleic acid is an essential precursor that animals convert into longer, more unsaturated acids with important physiological functions. Between 1920 and 1941 she published roughly thirty papers in the Biochemical Journal, many collaborative. In 1927 she co-authored the second edition of her husband’s book The Lipins (also known as Lecithin and Allied Substances). Her 1943 monograph The Metabolism of Fat, the first volume in Methuen’s series of biochemical monographs, summarized current knowledge of fatty-acid synthesis, the role of unsaturated acids, oxidation, and transport. It appeared shortly before her death and was reviewed as a concise, needed overview of a rapidly developing field.
MacLean combined laboratory work with determined advocacy for women in science and higher education. In 1907 she was among the founders of the British Federation of University Women (BFUW); she later served as secretary and as president from 1929 to 1935. The organization subsequently named a research fellowship after her. She also played a leading role in the International Federation of University Women and its fellowship programmes. Together with Martha Whiteley she campaigned for the admission of women to the Chemical Society. Petitions in 1904 and 1908 were rejected, but after the Sex Disqualification (Removal) Act of 1919 the Society admitted women; MacLean was among the first formally admitted in 1920 and served on its council from 1931 to 1934. She became a Fellow of the Royal Institute of Chemistry in 1918, one of the first three women elected to the Biochemical Society in 1913, and the first woman to chair that society (1927–1928). From 1941 to 1944 she sat on the University of Cambridge women’s appointments board. She also supported broader equality measures, including petitions for women’s suffrage in India and equal welfare payments. In 1925 she and Whiteley helped start the Women Chemists’ Dining Club to foster professional networks.
Ida Smedley MacLean died on 2 March 1944 at University College Hospital in London, aged 66, and was cremated at Golders Green. Obituaries in Nature by Winifred Cullis and Leslie Nunn praised both her scientific integrity and her service to university women. Her research on even-chain fatty acids, two-carbon building blocks, yeast metabolism, and the structure and nutritional role of arachidonic acid contributed directly to the later elucidation of essential fatty-acid pathways and eicosanoid biochemistry. At the same time, her institutional firsts—first woman on the Manchester chemistry staff, first formally admitted to the Chemical Society, early leadership in the Biochemical Society and the BFUW—helped change the professional landscape for women scientists in Britain. She demonstrated that rigorous original research and organized advocacy could proceed together, even under the constraints of marriage, motherhood, and wartime demands. Her life remains a model of scientific persistence and institutional reform in an era when both were unusually difficult for women.