The nutrient decline in food and what you can do about it 

The nutrient decline in food and what you can do about it 

You may have heard that the nutrient value of food is in decline, and that the carrots that land on our plate look and taste nothing like the carrots that our great-grandparents ate. 

This is, unfortunately, true – and the reasons are many. In December 2004, the Journal of the American College of Nutrition published a landmark study on the topic; researchers studied U.S. Department of Agriculture nutritional data from 1950 and 1999 for 43 different vegetables and fruits. They found varying levels of decline in the amount of protein, calcium, phosphorus, iron, riboflavin (vitamin B2) and vitamin C for those vegetables over the period. Since then, scientists around the world have divergent opinions regarding the extent and impact of the decrease in nutrient value – some say that we’re on our way to a nutrition collapse, while others say that it’s wildly exaggerated. Either way, it’s particularly troubling, given that nutritional deficiencies remain a huge public health concern and scientists are still figuring out what the implications will be. 

According to the Global Hunger Index, two billion people worldwide suffer from “hidden hunger”, where they are consuming enough calories, yet they are malnourished because of nutritional deficiencies. This includes those who are obese, partially caused by consuming calorie-rich and nutrient-poor food. In South Africa, the 2021 Global Nutrition Report estimates that 42.9% of adult women (aged 18 and over) and 18.2% of adult men are obese. Iron deficiency is the top nutritional disorder in the world; local reports indicate that 30.5% of women aged 15 to 49 years (reproductive age) are anaemic, with 14.2% of infants having a low birth weight. Meanwhile, one in three people worldwide are affected by inadequate zinc intake, and millions are deficient in calcium, magnesium or selenium. Nutritional deficiencies can lead to impaired cognitive and physical development in children, increased childhood and maternal deaths, and impaired immune function. 

What’s causing the nutrient decline? 

There are a number of reasons: 

Rising levels of carbon dioxide (CO₂) 

Plants need CO₂ to grow, so it might seem strange that too much carbon dioxide is actually unhealthy for plants. When the plant is exposed to higher levels of CO₂, this increases the rate of growth; the greater the accumulation of carbohydrates (glucose) leaves less room for other essential nutrients like protein and minerals (e.g. zinc and iron). Similar to junk food, the extra CO₂ causes the plants to grow bigger and faster, but it’s less nutrient-packed. The effects of this are so profound that increasing carbon dioxide in the air is reducing the protein in staple crops like rice, wheat, barley and potatoes. Scientists estimate that by 2050, 150 million people could be at risk of protein deficiency, particularly in countries like India and Bangladesh, where rice is a staple food. 

This has a ripple effect on animals as well. Another study from the US showed that the pollen eaten by bees contains less protein than it once did. 

Global warming also affects the biodiversity of the soil, impacting the types of plants that can grow soil, and hence, soil composition. 

The use of preferred cultivars* for higher yield

After food shortages, post-World War II, high-yield varieties of crops and breeds of livestock were developed to boost food production. Since then, selective breeding, agrochemicals, improved irrigation methods and the accessibility of affordable tractors, all led to an increase in crop productivity. The BBC reported that the average global cereal yield rose 175% between 1961 and 2014, with wheat, for example, rising from an average yield of 1.1 tonnes per hectare to 3.4 tonnes per hectare in around the same timeframe. This has led to “nutrient-dilution”. 

Soil overuse, which leads to mineral depletion 

Studies have shown that soil life influences both mineral uptake and phytochemical2 production in numerous crops. Similar to the beneficial bacteria in our digestive tracts, soil organisms also make nutrients biologically available to plants. A recent study published in Frontiers in Sustainable Food Systems (November 2021), reported that tillage and chemical fertilizers reduce the diversity and abundance of soil life, influencing nutrient cycling, crop mineral uptake, and phytochemical production. 

In the past 40 years, the world has also lost a third of its high-quality food-producing land due to erosion or pollution. 

The use of agrochemicals – synthetic fertilisers, pesticides and herbicides 

This has led to a loss of microbial life in soil. 

People eating less local, seasonal foods, along with a global food system 

Food processing, preparation and storage 

What does this mean for nutrition values on food labels? 

Food composition tables represent snapshots of nutrient compositions for foods at a particular time, so experts say that they offer some indication about the nutrient content of foods, but are far from reliable. They suggest that, instead, that nutrients should be reflected as a range. 

Steps towards a nutrient-dense diet: 

• Eat more nutrient-dense foods, e.g. salmon, kale, garlic, liver, potatoes, sardines, blueberries and egg yolks. Nutrient density refers to the amount of nutrients per calorie. [Read more – What is nutrient density?] 

• Eat fresh, local fruit and vegetables, in season. [Read more – Your Quick Guide to Season Fruit and Vegetables in South Africa]

• Make small swap outs, e.g. eat wholegrain bread and pasta instead of their refined versions. 

• Eat more nutritionally balanced versions of our frequently consumed products. 

• Reduce the amount of fats and salt that you use when cooking. 

• Grow your own nutrient-dense foods, such as kale. 

• Consider supplementing if you feel that you are not consuming enough micronutrients 

A cultivar is a plant variety produced by selective breeding.  

References
1. Bottemiller, H. (2017). The great nutrient collapse. Politico. Accessed on 23 February 2022. Available from https://www.politico.com/agenda/story/2017/09/13/food-nutrients-carbon-dioxide-000511/#:~:text=IN%20AGRICULTURAL%20RESEARCH%2C%20it’s%20been,past%2050%20to%2070%20years
2. Curcio, S. (2019). What’s Behind the Invisible Decline in Nutrient Density?. Medium [Online]. Accessed on 23 February 2022. Available from https://medium.com/@stacey_59725/whats-behind-the-invisible-decline-in-nutrient-density-b2227306992f
3. Eufic. (2021). What is nutrient density? Eufic [Online] Accessed on 24 February 2022. Available from https://www.eufic.org/en/understanding-science/article/what-is-nutrient-density
4. Global Nutrition Report. (2021). 2021 Global Nutrition Report (GNR). Global Nutrition Report [Online]. Accessed on 28 February 2022. Available from https://globalnutritionreport.org/resources/nutrition-profiles/africa/southern-africa/south-africa/
5. Gunnars, K. 2021. Healthline [Online]. Accessed on 1 March 2022. Available from https://www.healthline.com/nutrition/11-most-nutrient-dense-foods-on-the-planet#_noHeaderPrefixedContent
6. Lovell, R. (2022). How modern food can regain its nutrients. BBC. Accessed on 23 February 2022. Available from https://www.bbc.com/future/bespoke/follow-the-food/why-modern-food-lost-its-nutrients/
7. Montgomery, D.R and Anne Biklé, A. (2021). Soil Health and Nutrient Density: Beyond Organic vs. Conventional Farming. Frontiers in Sustainable Food Systems. 5:699147. Accessed on 28 February 2021. Available from https://doi.org/10.3389/fsufs.2021.699147
8. Scheer, R. & Moss, D. (2011). Dirt Poor: Have Fruits and Vegetables Become Less Nutritious?. Scientific American [Online] Accessed on 23 February 2022. Available from https://www.scientificamerican.com/article/soil-depletion-and-nutrition-loss/
9. Suglia, E. (2018). Vanishing Nutrients. Scientific American Blog Network [Online] Accessed on 28 February 2022. Available from https://blogs.scientificamerican.com/observations/vanishing-nutrients/
10. Wikipedia. (2022). Phytochemical. Wikipedia. Accessed on 28 February 2022. Available from https://en.wikipedia.org/wiki/Phytochemical

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