Mineral nutrient composition of vegetables, fruits and grains: The context of reports of apparent historical declines

Reports of apparent historical declines in mineral nutrients of vegetables, fruits and grains, allegedly due to soil mineral depletion by agriculture, triggered this critical review. Comparisons of food composition data published decades apart are not reliable. Over time changes in data sources, crop varieties, geographic origin, ripeness, sample size, sampling methods, laboratory analysis and statistical treatment affect reported nutrient levels. Comparisons with matching archived soil samples show soil mineral content has not declined in locations cultivated intensively with various fertilizer treatments. Contemporaneous analyses of modern versus old crop varieties grown side-by-side, and archived samples, show lower mineral concentrations in varieties bred for higher yields where increased carbohydrate is not accompanied by proportional increases in minerals - a “dilution effect”. Apparent declines, e.g., the extreme case of copper from −34% to −81%, represent small absolute changes: per 100 g dry weight vegetables have 0.11-1.71 mg (1555% natural range of variation), fruit 01-2.06 mg (20,600% range), and grains 0.1-1.4 mg (1400% range); copper composition is strongly subject to the dilution effect. The benefits of increased yield to supply food for expanding populations outweigh small nutrient dilution effects addressed by eating the recommended daily servings of vegetables, fruits and whole grains.