Food for Health: Considering the Nutrient Density of Food Crops

Read Time: 7 Minutes

Research studies suggest that the nutrient content of crops has declined over the years,1-4 possibly due in part to agricultural methods, land and soil management practices, and climate change.5-7 A potential decline in food crop nutrient density is important to consider when addressing micronutrient malnutrition, preventing chronic diseases, and promoting optimal health.

The human body requires certain levels of micronutrients for normal body processes, and deficiencies in one or more micronutrients may lead to detrimental health issues. Nutrient shortfalls have already been noted within the US population,8 and reporting indicates that most Americans do not consume the recommended amounts of micronutrient-rich fruits and vegetables.9 Health organizations have reported on micronutrient malnutrition, including iodine, iron, and vitamin A, that continues to have devastating consequences for billions of people across the globe.10 Micronutrient inadequacies and deficiencies have been associated with a wide range of physiological impairments, including metabolic disorders11 and reduced immune,12 endocrine,13 and cognitive functions.14

Nutrient Content of Food Crops: A Focus on Soil

Several factors may contribute to the reported micronutrient deficiencies in populations, including dietary patterns and the prevalence of a Western-style diet consisting of more processed foods and less phytonutrient-rich vegetables.15 Additionally, reduction in the nutrient density of food crops has the potential to exacerbate micronutrient malnutrition. Soil health and how climate factors impact nutrients in food crops are important areas of current research.16,17

An important indicator of soil health is soil respiration, which is essentially a measure of carbon dioxide (CO2) released from the soil due to the decomposition of organic matter by microbes within the soil.18 This measurement indicates the level of soil microbial activity, the nutrients available in the soil for uptake by crops, and the soil’s ability to sustain plant growth.18 Maintaining a diverse soil biota is essential for agricultural sustainability for both productive and nutrient-dense crop yields.19 In 2016, a government report on US soils suggested that land-use changes in the past 50 years have contributed to reduced ecosystem functions.7 When combined with intensive agricultural practices and soil contamination, this has the potential to reduce soil microbial abundance and impair other functions such as decomposition and nutrient retention.7

Climate factors can also affect soil health, from moisture levels20 to the level and availability of nutrients such as nitrogen, phosphorus, potassium, and iron.6 One consideration is that warming air temperatures and increased solar radiation may lead to higher soil temperatures, resulting in more microbial activity, higher soil respiration rates, and potential limitations in soil nutrient availability.7

The soil provides many nutrients that plants and humans require, creating a link between soil health and human health. As an example, soil can become acidic for a variety of reasons, including repeated harvesting of high-yielding crops, and the resulting magnesium deficiency negatively affects soil conditions, the sustainability of crop production,21 and potentially the amount of magnesium available when the crop is consumed. A 2020 meta-analysis of 99 field research articles that studied effects of magnesium fertilization on crop production suggested that the magnesium supplementation directly affected the levels of magnesium accumulated in the plant leaf tissues, with an increase of 34.3% on average.21 Continuing research suggests that crops grown on soils containing all the major nutrients for plants often have higher yields and higher nutrient concentrations; however, whether this is true for all types of crops and what soil factors and management techniques yield the most nutrient-dense crops is not well understood.5

Climate Change – From Crops to People

Recent research notes that atmospheric carbon dioxide (eCO2) levels may contribute to the fluctuation of nutrient availability in soil and nutrient uptake by crops, as well as the resulting levels of minerals and proteins in those plants that are ultimately consumed by people.6,22,23 However, the climate-related mechanisms for potential declines in plant mineral composition are not completely understood, and the argument is made that eCO2 potentially enhances overall crop yield, which may be a benefit in some situations, even if the mineral quality of the crop is decreased.6

As the research continues to develop, an important 2014 meta-analysis of 7,761 observations, including 2,264 observations at free air CO2 enrichment (FACE) centers and including 130 species, suggested that elevated CO2 levels reduced the overall concentration of 25 minerals in plants, including calcium, potassium, zinc, and iron, by 8%, on average.24 In addition, this increased CO2 exposure increased the ratio of carbohydrates to minerals in the studied plants.24 A 2017 review found that elevated CO2 concentrations potentially resulted in a 3-11% decrease in zinc and iron in cereal grains and legumes, specifically.22 In addition to minerals, elevated eCO2 potentially impacts the protein concentration of various grains, which may significantly affect countries that rely on grain crops as sources of dietary protein.6,25,26

Increased levels of eCO2 potentially increase the yield of various crops through the enhancement of their photosynthetic rates.6,27 However, the impact on nutritional quality of those crops is an important consideration in the scope of micronutrient malnutrition concerns. A 2018 meta-analysis that used 57 articles consisting of 1,015 observations found that eCO2 increased the concentrations of sugars, antioxidant capacity, phenols, flavonoids, ascorbic acid, and calcium in the edible part of vegetables but decreased the concentrations of protein, nitrate, magnesium, iron, and zinc at the following noted percentages:27

  • Decreases in magnesium concentrations were at 9.2%.
  • Decreases in zinc concentrations were at 18.1% in both fruit and root vegetables and 10.7% in stem vegetables.
  • Decreases in iron concentrations were greatest in leafy vegetables at 31%, followed by fruit vegetables (19.2%) and root vegetables (8.2%).
Food Crops: Organic vs Nonorganic

Consuming organically farmed foods over non-organic may help reduce exposures to environmental toxicants such as pesticides and may be associated with health benefits.28-30 While confounders such as increased health-conscious behavior and more favorable social determinants of health may influence research results, a 2022 meta-analysis of four observational studies (n=104,488 healthy adults) found that compared to a non-organic diet, those who consumed organic food had an 11% lower probability of obesity.31

While some studies suggest that the overall mineral and vitamin levels in plants may not be significantly impacted by the method of crop production,32 higher content levels of polyphenolic compounds in organic food crops have been found.33 A 2014 systematic review and meta-analysis of 343 peer-reviewed publications found that concentrations of antioxidants such as polyphenols were much higher in organic crops and organic crop–based foods.33 Specifically, the analysis found the following chemicals and estimated percentages:33

  • Phenolic acids – 19% higher concentration in organic crops
  • Flavanones – 69% higher concentration in organic crops
  • Stilbenes – 28% higher concentration in organic crops
  • Flavones – 26% higher concentration in organic crops
  • Flavonols – 50% higher concentration in organic crops
  • Anthocyanins – 51% higher concentration in organic crops

Translating the Research for Clinical Applications

Personalized nutritional interventions are cornerstones of functional medicine care, and assessment of micronutrient inadequacies, deficiencies, or risk of deficiency is essential during clinical intake. Micronutrient malnutrition may not be immediately obvious, yet addressing any nutrient deficiency has the potential to improve or resolve many health concerns. Any decline of essential micronutrients in food crops is an important clinical consideration that may help inform personalized nutritional approaches for chronic disease treatment or prevention strategies.

Within the functional medicine model, a comprehensive view of a patient’s historical and current medical, social, family, and personal story helps to organize and prioritize their health concerns and determine appropriate interventions for each individual patient. Assessment tools such as the nutrition-oriented physical exam help detect imbalances by performing the physical exam through a nutritional lens. In addition, nutrition intake assessments and food diaries help determine amounts of nutrients consumed, help evaluate the variety of food choices, and may help inform treatment strategy. Additional clinical resources found in the extensive toolkit for IFM members also help to evaluate a patient’s potential toxicant exposures, including through diet.

For a deeper understanding of micronutrient imbalances and how personalized lifestyle-based therapies can address these and other health imbalances, learn from the functional medicine experts at IFM’s Applying Functional Medicine in Clinical Practice (AFMCP).

Learn More About Functional Medicine


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