Fewer nutrients in our vegetables? Why?

The nutrient density in our diet has significantly decreased over the past 70 years.

The nutrient density of our edible plants, such as vegetables, fruit and wheat, has decreased in recent decades. Especially after the Second World War, we humans have developed ever better methods to grow even more wheat, vegetables or fruit on a given area. There are more and more grains of wheat per plant and vegetables have become bigger and plumper. The global wheat harvest, for example, has increased by over 200% on a comparable area of land since 1961 [1]. Although we have been able to grow and harvest more and more, the quality of the food produced has declined. A study in the USA compared the nutrient content of 43 fruits and vegetables from 1950 with the same fruits and vegetables from 1999. For 6 of the 13 nutrients analysed, such as proteins, calcium and iron, a significant decline was found in the foods. However, it was also noted that the decrease was not the same for all foods or even increased in some cases [2]. Two main reasons are given for the decline in nutrients:

Higher CO2 levels in the atmosphere due to climate change. Studies show that this increase means that wheat plants can convert more CO2 into starch through photosynthesis. This relative increase in starch causes the ratio between starch and minerals/vitamins to shift more and more in favour of starch, which leads to a dilution of nutrients [3]. 2. Adaptation of the plants. In cereal plants, for example, the stalk was bred smaller and smaller (see image) so that the plant had to invest less energy in growth and at the same time became more robust. As less energy is invested in the growth of the plant, more energy can be stored in the form of starch in the grains [4].

The studies provide insights into a nutrient dilution that occurred between 1950 and 1999 and suggest that this trend is likely to continue to the present day. Although the optimization of global harvests has brought about positive aspects, it can exacerbate nutrient deficiencies in our regions. Considering that we humans are taking in fewer nutrients through plants, it is likely to be similar for the animals we, in turn, consume. When dealing with a nutrient deficiency, it is advisable to delve into this topic and increase consumption of fruits, vegetables, and grains from sustainable sources or to supplement the missing nutrients.

Sources:

[1] https://ourworldindata.org/yields-vs-land-use-how-has-the-world-produced-enough-food-for-a-growing-population

[2] Davis DR, Epp MD, Riordan HD. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. J Am Coll Nutr. 2004 Dec;23(6):669-82. doi: 10.1080/07315724.2004.10719409. PMID: 15637215.

[3] Degener, Jan. 2015. „Atmospheric CO2 fertilization effects on biomass yields of 10 crops in northern Germany“. Frontiers in Environmental Science 3. doi: 10.3389/fenvs.2015.00048.

[4] Friedli, C.N., Abiven, S., Fossati, D. et al. Modern wheat semi-dwarfs root deep on demand: response of rooting depth to drought in a set of Swiss era wheats covering 100 years of breeding. Euphytica 215, 85 (2019). https://doi.org/10.1007/s10681-019-2404-7

Fewer nutrients in our vegetables? Why?

The nutrient density in our diet has significantly decreased over the past 70 years.

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