For diet reconstruction, carbon and nitrogen isotope ratios in bone collagen are particularly informative. Nitrogen isotope ratios reflect the position of an organism in the food chain: carnivores and fish-eaters show higher nitrogen-15 values than herbivores, and humans who consume large amounts of protein from animal sources, including fish and shellfish, show elevated nitrogen-15 ratios compared to those who subsist more heavily on plant foods. Carbon isotope ratios distinguish between different photosynthetic pathways in plants and can distinguish between marine and terrestrial food sources.
For geographic mobility, strontium and oxygen isotopes in tooth enamel are useful. Strontium in bedrock varies by geological composition, and this variation is reflected in the plants and animals of a region and ultimately in the people who consume them. Teeth form during childhood and their isotopic composition is fixed at that point, making tooth enamel a record of where a person spent their early years. If an individual’s tooth enamel strontium ratios differ from what is typical of the local geology, this can indicate that the person grew up elsewhere and moved to their burial location during their lifetime.
Specific isotope data for Cheddar Man from sources accessed for this article is not detailed in what was accessible, and it would be inaccurate to state particular isotopic values or dietary reconstructions without verified source material. What is generally known about Mesolithic hunter-gatherers in Britain — from isotope studies of other Mesolithic individuals from the region and period — is that their diets were typically rich in animal protein, including freshwater and marine fish and shellfish in coastal and riverine contexts, alongside terrestrial game. The Cheddar Gorge area, with the River Yeo nearby and access to the Bristol Channel and its coastal resources, would have offered abundant opportunities for fishing as well as terrestrial hunting.