{"url":"https://whatshealthyandwhy.com/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious","path":"/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious.json","markdown":"https://whatshealthyandwhy.com/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious.md"},"topic":{"slug":"nutrient-decline-in-modern-crops","name":"Nutrient Decline in Modern Crops","url":"https://whatshealthyandwhy.com/nutrient-decline-in-modern-crops"},"slug":"has-soil-depletion-made-food-less-nutritious","order":1,"title":"Has Soil Depletion Made Our Food Less Nutritious?","question":"Has soil depletion made fruits and vegetables less nutritious?","answer":"Some minerals have likely fallen in some crops, but depleted soil is not the best-supported cause; high-yield varieties and rising CO2 fit better.","description":"Some minerals have fallen in modern crops, but high-yield varieties and rising CO2 fit the evidence better than tired soil. What the data show and what to eat.","confidence":3,"confidenceNote":"Declines in some minerals appear in several independent datasets, but food-table comparisons are shaky, the causes are debated, and evidence on health effects is limited and mostly observational.","evidenceSummary":{"rctCount":0,"observationalCount":7,"metaAnalysisCount":3,"replicated":true,"newestStudyYear":2023},"category":{"categoryTitle":"How to Live","categorySlug":"how-to-live","subcategoryName":"Plants, Garden & Soil","subcategorySlug":"garden","url":"https://whatshealthyandwhy.com/explore/how-to-live/garden"},"actions":["Eat more fruits and vegetables of many kinds, fresh or frozen: each extra 200 g a day was linked to about 10% lower all-cause mortality in a 95-study meta-analysis [4].","Buy frozen when fresh produce has sat for days: vitamin content of frozen produce was comparable to, and sometimes higher than, fresh produce kept cold [5].","Eat a mix of whole grains, beans, nuts, seeds and vegetables; grain minerals such as selenium and zinc vary with soil and region, so variety is the safest hedge [6]."],"cautions":["Do not self-prescribe minerals for 'depleted' food: soil shortfalls are real in some regions (selenium in Finland before 1984 [7]); with symptoms or local foods, ask a clinician to test.","Evidence that regenerative or 'nutrient-dense' produce improves health is preliminary (small samples, paired farms [8]); health harm from intensive farming is limited and observational [9]; do not skip affordable produce."],"simpleText":"Comparisons of food composition tables suggest some nutrients, including iron and vitamin C, are lower in modern vegetables than in 1950s ones [1], and UK tables show iron and copper in fruit and vegetables about halved since 1940 [2]. But depleted soil does not look like the main cause: in a 160-year wheat archive, soil minerals held steady while grain minerals fell once high-yielding varieties arrived [3]. Vegetables remain very good for you [4].","mediumText":"How it works\n\nThe claim\n\nDavis and colleagues compared US government composition tables for 43 garden crops from 1950 and 1999. As a group the crops showed apparent declines in protein, calcium, phosphorus, iron, riboflavin and vitamin C, with median declines from 6% for protein to 38% for riboflavin [1]. But for individual foods most changes could not be told apart from no change, and about 28% of the ratios went up [1]. A UK analysis of national tables from 1940, 1991 and 2019 found that every mineral except phosphorus fell in fruit and vegetables, with iron down about 50%, copper 49% and magnesium 10% [2].\n\nWhy soil is probably not the main reason\n\nAt Rothamsted in England, archived wheat grain and soil from the Broadbalk experiment (begun in 1843) showed that zinc, iron, copper and magnesium in grain were stable until the mid-1960s and then fell as high-yielding, semi-dwarf varieties arrived. Soil levels were stable or higher, and grain fell with no fertilizer, inorganic fertilizer or manure alike [3]. Higher yield and harvest index explained the trend, a pattern often called the dilution effect: a plant that makes more grain ends up with a smaller share of minerals in each bite [3].\n\nRising carbon dioxide\n\nCrops grown in field experiments at the carbon dioxide levels expected by the middle of this century had less zinc and iron, and, outside legumes, less protein [10]. A meta-analysis of 7,761 observations found that elevated CO2 lowered overall mineral concentrations in C3 plants, such as wheat and rice, by about 8% [11].\n\nWhere soil does matter\n\nSome soils are naturally low in particular minerals. Cereal selenium and zinc in Ethiopia and Malawi varied with soil pH, organic matter and rainfall, and for people eating locally grown grain, where they live can be the biggest influence on intake [6]. Finland corrected a very low selenium intake by adding selenium to fertilizer: cereal selenium rose 15-fold and average plasma selenium moved from 0.89 to 1.40 micromoles per liter [7]. See Selenium.\n\nRegenerative farming\n\nPaired-farm comparisons suggest that regenerative practices such as no-till, cover crops and diverse rotations can raise some vitamins, minerals and phytochemicals, but the samples were small and the authors call the results preliminary [8]. A narrative review concluded that agricultural intensification has lowered some desirable compounds, while evidence of health harm is limited and mostly observational [9].\n\nWhat to do\n\nEat more produce, fresh or frozen. Frozen fruit and vegetables kept their vitamins as well as fresh ones stored cold, although beta-carotene fell in some items [5]. See also Organic vs. Conventional.","deepText":"The evidence in detail\n\nFood-table comparisons\n\nDavis and colleagues compared published USDA data for 13 nutrients and water in 43 garden crops, mostly vegetables, between 1950 and 1999, adjusting for moisture [1]. As a group the foods showed statistically reliable declines in protein, calcium, phosphorus, iron, riboflavin and vitamin C but not in seven other nutrients; median declines ranged from 6% for protein to 38% for riboflavin [1]. For individual foods and nutrients most ratios could not be distinguished from 1, about 28% exceeded 1, and because the 1950 values lacked error estimates the authors had to model the uncertainty [1]. They proposed that any real declines are most easily explained by changes in cultivated varieties, with trade-offs between yield and nutrient content [1]. A limitation of any table comparison is that editions rest on different samples, varieties and laboratory methods, so a difference may not be a real change.\n\nMayer and colleagues compared the UK's Composition of Foods tables from 1940, 1991 and 2019 and found that every element except phosphorus declined in fruit and vegetables over 80 years: sodium by 52%, iron by 50%, copper by 49% and magnesium by 10%, while water content rose by 1% [2]. They suggest changes in crop varieties, agronomic factors and rising CO2 as possible reasons and call for investigation [2].\n\nArchived grain: the strongest test\n\nFan and colleagues measured minerals in archived wheat grain and soil from the Broadbalk experiment at Rothamsted, established in 1843 [3]. Zinc, iron, copper and magnesium concentrations were stable from 1845 to the mid-1960s and then fell significantly, coinciding with semi-dwarf, high-yielding cultivars, while soil concentrations were stable or rising [3]. The decline appeared in plots receiving no fertilizer, inorganic fertilizer or manure, and multiple regression showed that yield and harvest index explained the downward trend [3]. Limitations: one site and one crop, grain rather than vegetables. Debnath and colleagues compared landmark high-yielding rice and wheat cultivars released in India since the Green Revolution and reported that zinc and iron fell by about 33% and 27% in rice and by 30% and 19% in wheat over more than 50 years, alongside a rise in toxic elements [12].\n\nCarbon dioxide\n\nMyers and colleagues' meta-analysis of field experiments found that C3 grains and legumes grown at the CO2 concentration predicted for mid-century had lower zinc and iron, C3 crops other than legumes had lower protein, and C4 crops seemed less affected [10]. Loladze's meta-analysis of 7,761 observations, including 2,264 from free-air CO2 enrichment centers and covering 130 species and cultivars, found that elevated CO2 lowered overall mineral concentration in C3 plants by 8% (95% CI -9.1 to -6.9) [11]. Limitations: these experiments simulate future concentrations, and how much of the past decline CO2 explains is unclear.\n\nSoil matters, but not as \"depletion\"\n\nGashu and colleagues mapped calcium, iron, selenium and zinc in staple cereal grains across Ethiopia and Malawi and found that grain micronutrients varied geospatially with soil pH, organic matter, temperature, rainfall and topography, and that grain selenium related to biomarkers of selenium status [6]. In Finland, adding selenium to fertilizers from 1985 raised spring cereal selenium about 15-fold, and average plasma selenium rose from 0.89 to 1.40 micromoles per liter [7]. These are cases of naturally low-mineral soils and regional geography rather than modern farming exhausting the ground.\n\nRegenerative farming\n\nMontgomery and colleagues compared crops from paired US farms using conventional or regenerative practices for 5-10 years [8]. Regenerative fields had higher soil organic matter and soil health scores and higher levels of certain vitamins, minerals and phytochemicals, and wheat from adjacent no-till fields in Oregon had a higher density of mineral micronutrients on the regenerative side [8]. Despite small sample sizes, the authors call this preliminary support. A narrative review concluded that agricultural intensification has lowered some desirable compounds, such as certain vitamins, selenium, zinc and phenolics, and raised others, such as cadmium and pesticide residues, while evidence of health harm is limited and based mainly on observational studies [9].\n\nDoes it matter for health?\n\nIn a meta-analysis of 95 prospective studies, each 200 g a day of fruit and vegetables was associated with a relative risk of 0.92 for coronary heart disease (95% CI 0.90-0.94), 0.84 for stroke (0.76-0.92), 0.97 for total cancer (0.95-0.99) and 0.90 for all-cause mortality (0.87-0.93), with reductions seen up to 800 g a day (600 g for cancer) [4]. Those associations were measured with today's produce. In eight fruits and vegetables, frozen samples had vitamin C, riboflavin and alpha-tocopherol levels comparable to, and sometimes higher than, refrigerated samples, though peas and carrots were lower in beta-carotene when frozen [5].\n\nBottom line (confidence 3 of 5)\n\nSeveral independent datasets show lower concentrations of some minerals in modern grains, and probably in some vegetables, although table comparisons are imperfect. Breeding for yield and rising CO2 explain the pattern better than depleted soil, and soil still matters regionally for selenium and zinc. Health effects are unproven. The practical message is unchanged: eat plenty of varied produce.","deepTruncated":false,"references":[{"id":"1","title":"Changes in USDA food composition data for 43 garden crops, 1950 to 1999","authors":"Davis DR, Epp MD, Riordan HD","year":2004,"journal":"J Am Coll Nutr","pmid":"15637215","url":"https://pubmed.ncbi.nlm.nih.gov/15637215/"},{"id":"2","title":"Historical changes in the mineral content of fruit and vegetables in the UK from 1940 to 2019: a concern for human nutrition and agriculture","authors":"Mayer AB, Trenchard L, Rayns F","year":2022,"journal":"Int J Food Sci Nutr","pmid":"34651542","url":"https://pubmed.ncbi.nlm.nih.gov/34651542/"},{"id":"3","title":"Evidence of decreasing mineral density in wheat grain over the last 160 years","authors":"Fan MS, Zhao FJ, Fairweather-Tait SJ, et al.","year":2008,"journal":"J Trace Elem Med Biol","pmid":"19013359","url":"https://pubmed.ncbi.nlm.nih.gov/19013359/"},{"id":"4","title":"Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies","authors":"Aune D, Giovannucci E, Boffetta P, et al.","year":2017,"journal":"Int J Epidemiol","pmid":"28338764","url":"https://pubmed.ncbi.nlm.nih.gov/28338764/"},{"id":"5","title":"Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage","authors":"Bouzari A, Holstege D, Barrett DM","year":2015,"journal":"J Agric Food Chem","pmid":"25526594","url":"https://pubmed.ncbi.nlm.nih.gov/25526594/"},{"id":"6","title":"The nutritional quality of cereals varies geospatially in Ethiopia and Malawi","authors":"Gashu D, Nalivata PC, Amede T, et al.","year":2021,"journal":"Nature","pmid":"34012114","url":"https://pubmed.ncbi.nlm.nih.gov/34012114/"},{"id":"7","title":"Effects of nationwide addition of selenium to fertilizers on foods, and animal and human health in Finland: From deficiency to optimal selenium status of the population","authors":"Alfthan G, Eurola M, Ekholm P, et al.","year":2015,"journal":"J Trace Elem Med Biol","pmid":"24908353","url":"https://pubmed.ncbi.nlm.nih.gov/24908353/"},{"id":"8","title":"Soil health and nutrient density: preliminary comparison of regenerative and conventional farming","authors":"Montgomery DR, Biklé A, Archuleta R, et al.","year":2022,"journal":"PeerJ","pmid":"35127297","url":"https://pubmed.ncbi.nlm.nih.gov/35127297/"},{"id":"9","title":"Effects of Agricultural Intensification on Mediterranean Diets: A Narrative Review","authors":"Hasanaliyeva G, Sufar EK, Wang J, et al.","year":2023,"journal":"Foods","pmid":"37893672","url":"https://pubmed.ncbi.nlm.nih.gov/37893672/"},{"id":"10","title":"Increasing CO2 threatens human nutrition","authors":"Myers SS, Zanobetti A, Kloog I, et al.","year":2014,"journal":"Nature","pmid":"24805231","url":"https://pubmed.ncbi.nlm.nih.gov/24805231/"},{"id":"11","title":"Hidden shift of the ionome of plants exposed to elevated CO₂depletes minerals at the base of human nutrition","authors":"Loladze I","year":2014,"journal":"Elife","pmid":"24867639","url":"https://pubmed.ncbi.nlm.nih.gov/24867639/"},{"id":"12","title":"Historical shifting in grain mineral density of landmark rice and wheat cultivars released over the past 50 years in India","authors":"Debnath S, Dey A, Khanam R, et al.","year":2023,"journal":"Sci Rep","pmid":"38036556","url":"https://pubmed.ncbi.nlm.nih.gov/38036556/"}],"wordCount":1338,"source":{"path":"src/content/topics/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious.md"},"citeAs":"“Has soil depletion made fruits and vegetables less nutritious?.” What's Healthy and Why. https://whatshealthyandwhy.com/nutrient-decline-in-modern-crops/has-soil-depletion-made-food-less-nutritious","notice":"General information backed by peer-reviewed research, not medical advice."}