Carbohydrates are built from simple sugars such as glucose linked into chains or rings. Haworth combined X-ray diffraction with chemical degradation to prove that simple sugars adopt cyclic structures and can exist as α- and β-anomers. He also showed that vitamin C (ascorbic acid) has a six-membered ring and clarified why it is a strong reducing agent. These findings impact not only nutrition but also industrial uses such as modifying cellulose for paper and textiles and developing antioxidant techniques for food preservation. Thus his work benefits both public health and manufacturing.

Using the then-new X-ray crystallography and optical rotation measurements, Haworth determined the stereochemistry of many monosaccharides such as glucose and fructose. He established that monosaccharides predominantly exist as cyclic hemiacetals and undergo anomeric interconversion, and he introduced the widely used Haworth projection. By improving the Remsen–Hirst oxidation, he proved that ascorbic acid possesses an enol-lactone skeleton. This structural insight made chemical synthesis feasible, leading to large-scale production before and after World War II. His work launched glycoscience, antioxidant research and medicinal chemistry, laying the foundation for today’s carbohydrate chemistry and dietary supplement industries.

Haworth devised selective protection strategies for aldohexoses, distinguishing C-1 and C-6 functionalities through partial oxidation with molybdenum catalysts. Single-crystal X-ray data and intensity pattern analysis allowed him to identify the 1C4 ↔ 4C1 chair inversion and demonstrate the dominance of β-D-pyranose in glucose. For ascorbic acid he quantified redox potentials via UV-Vis spectroscopy and zone electrophoresis, proposing that enolization and resonance stabilization account for its high reducing power. These methodological advances directly influenced stereoselective carbohydrate synthesis, oxidation catalyst design and modern glycan-profiling technologies.