Agriculture has dramatically increased the amount of food produced per hectare, but some crops may now contain fewer minerals per serving. A report by Deep Science Ventures and the Mark Leonard Trust argues that breeding crops primarily for higher yields may have contributed to this nutrient dilution.
Evidence from Rothamsted Research's long-running wheat experiment points to a notable shift: mineral levels in archived grain were broadly stable until the mid-1960s, then fell after shorter, higher-yielding varieties were introduced. Compared with older wheat, modern grain contained around 23 to 49 percent less of certain minerals, including zinc, iron, copper and magnesium.
Findings for fruits and vegetables vary by crop and nutrient. A comparison of British food-composition records found average iron levels in these foods had declined by about half between 1940 and 2019, while copper also fell and magnesium showed a smaller reduction. Researchers caution that these historical comparisons do not mean every fruit or vegetable has changed by the same amount.
Climate adds another factor
Higher atmospheric carbon dioxide can encourage some plants to produce more carbohydrates without a matching increase in minerals. A 2025 meta-analysis led by Leiden University researchers found widespread changes in crop chemistry under elevated carbon dioxide, with zinc among the nutrients of concern. The effects differ across crops, and rainfall patterns, soil conditions and farming practices also matter.
The issue is particularly relevant when people consume fewer calories. A model in the report examined a hypothetical scenario in which 15 percent of working-age adults in Britain used GLP-1 medicines and ate less, alongside a decline in crop nutrient density. Under those assumptions, around five million more people could risk falling below very low intake thresholds for essential nutrients. This is a modelled scenario, not a forecast.
Breeding for nourishment as well as yield
Research in Nature Food suggests that crop choices and farming practices can help address the challenge: wheat varieties selected for higher zinc content had greater mineral levels, while combined zinc and iron fertilisers increased grain concentrations in the study. The report also highlights soil health, nutrient-rich crop breeding and food fortification as potential tools.
Future agricultural progress may depend on measuring not only how much food fields produce, but also how much nourishment each harvest provides.
