
Sigma Nutrition Radio #590: Is the Nutrient Density of Crops Declining? – Edward Joy, PhD
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Jan 13, 2026 Dr. Edward Joy, a senior research fellow specializing in agriculture and nutrition, dives into the pressing issue of nutrient density in crops. He discusses how modern farming practices and soil health may be causing declines in essential micronutrients like iron and zinc. Through historical evidence, he highlights shifts in crop composition since the 1970s. Dr. Joy also explores potential solutions, including breeding strategies and soil management techniques, emphasizing the importance of nutrient-rich staples for public health and tackling hidden hunger.
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What Nutrient Density Actually Means
- Nutrient density is micronutrient mass divided by edible crop mass and varies by species and tissue.
- Plant genetics, environment, and crop management jointly determine micronutrient concentration in foods.
Historical Drop Linked To Green Revolution
- Rothamsted's Broadbalk archive shows wheat micronutrient densities were stable until ~1970 then fell sharply.
- The decline coincided with Green Revolution semi-dwarf varieties that greatly increased yield but lowered mineral density.
Genetics Versus Soil: Different Drivers
- The Broadbalk decline occurred despite stable plant-available soil zinc, implicating crop genetics rather than soil loss.
- In contrast, older tropical soils can be zinc-poor and soil management there strongly affects crop micronutrients.
