The decline in the nutrient content of our food

The important role that micronutrients play in our health is well documented, but despite this it is becoming increasingly challenging for most of us to achieve a suitable intake.

Micronutrient malnutrition (a term used to refer to conditions caused by a dietary deficiency of vitamins or minerals) is now widespread^1,3 and there are many contributing factors. One notable impact is the health of the soil in which our fresh foods grow and the effect of modern agricultural methods. In a recent study published in 2021, it was found that fruit and vegetables sold in the UK now only contain around half the amount of key nutrients than they did in 1940.²

For the purpose of this blog, we will therefore explore the impact of the soil on the nutrient content of our food, the detrimental effects of modern farming practices, and practical strategies to help us to replete diminishing nutrients.

Past and Present
Not only do our diets tend to be low in fruit and vegetables nowadays but the ones that we are consuming are a far cry from those that were consumed 50-100 years ago. In bygone days, an eco-balance of healthy, mineral-rich soil, maintained by animal waste and natural colonies of soil bacteria meant seasonally produced plants grew rich in minerals and provided humans and animals with the minerals and phytonutrients they needed for health.

Enhanced production techniques after WW2 resulted in higher yields, faster growing times, and chemical pest control. These practices helped to grow food in abundance, but the compromise was the soil was left impoverished and without a rest period to regain the depleted micronutrients. As a result, each generation of our fruit and veg has often been less nutritious than the last.

This decrease in micronutrients has been shown in a recent study which analysed the mineral content of fruits and vegetables from three editions of the UK’s Composition of Foods Tables (1940, 1991 and 2019). Most elements declined in concentrations between 1940 and 2019 – the greatest reductions were iron (50%), Copper (49%) and magnesium (10%).²

So, let us look further at some of the different factors that may be affecting the nutrient content of our fresh foods.

Skip to Key Takeaways

Crop varieties and the ‘dilution effect’
Farmers nowadays often specialise in growing just one crop to maximise profits and reduce costs (monoculture). This reduces key nutrients in the soil, lowers biodiversity and may result in higher pesticide and fertiliser use. Most varieties of fruit and vegetables eaten today therefore have been bred to improve productivity and the emphasis on yield has essentially overlooked any implications for nutritional quality.² Faster growing crops for example, do not allow the plant to manufacture or uptake nutrients at a similar rate. One researcher attributed this to a ‘dilution effect’, whereby yield increases, and so also does dry matter and carbohydrate but without a parallel increase in minerals.¹³

Origin, transportation and storage
Fresh fruits and vegetables are perishable and extremely prone to nutritional losses. During the 1940s most of our fruit and veg was grown here in the UK so there was less time for nutrients to deplete before consumption. Although a rise in imports has increased the availability and diversity of fruit and veg, a large percentage of the nutritional value is likely lost during preparation, transportation and storage. The contribution of UK production to total fruit and vegetable supply decreased from 42% in 1987 to 22% in 2013, meaning the largest proportion is now imported.⁵

Early harvesting and artificial ripening
Our desire for all-year-round (out of season) fruit and veg from around the globe is met by early picking, cold storage, and rapid ripening. Fruit therefore does not have a fully developed nutrient potential, and storage depletes the vitamin content.

Soil microbiology
The soil relies on the biodiversity of naturally occurring organisms including bacteria, fungi, worms and insects for its health, and plants take up minerals in conjunction with a complex relationship with these organisms.² There has however been a severe decline of colonies of soil organisms due to intensive agriculture.

The term ‘mycorrhiza’ refers to the role of the fungus in the plant’s root system and is a symbiotic relationship that provides a bidirectional nutrient transfer. This enables better uptake of soil nutrients as a larger volume of soil can be effectively utilised by the plants.² Mycorrhizal dynamics are a vital element of agriculture but again, there has been a decline in these dymanics.^7-12

Pesticides and herbicides
The weakening of the soil and crops through the practices of commercial agriculture creates a dependence on the use of pesticides and herbicides to maintain crop yield. These however can be toxic and destroy the symbiotic bacteria and fungi that promote nutrient uptake in plants.

Deep ploughing
Deep ploughing can also disrupt the natural microbiome of the soil and can upset the mycorrhiza essential for the transformation of inorganic minerals to organic forms that can be metabolised by plants.

NPK fertilisers
The use of fertilisers, particularly those containing nitrogen, phosphorus and potassium (NPK) increased rapidly from the 1940s onwards, increasing crop yields.² The reason for the NPK mixture is that scientists found that these were the three minerals that encouraged plants to grow quickly. Growing plants can however use up to 60 minerals and trace minerals. The standard use of ‘NPK’ fertilisers deprives the soil of the many remaining nutrients that would normally be present.⁷

Soil-less growing techniques
Field vegetables and top fruit are still grown in soil but almost all UK conventional protected fruit crops (e.g. tomatoes, peppers and aubergines) are produced in soil-less culture such as hydroponics. These systems are optimised to maximise yield, but often the nutritional value of the produce is not always considered.²

Climate change
Plants require CO2 to grow and thrive and while rising levels can boost plant productivity and yields, they can disrupt the plants’ internal chemistry. For example, higher levels can increase the amount of carbohydrate the plant produces, which often comes at the detriment of micronutrients.

Impacts
All of the discussed factors have meant that there has been a large reduction in the micronutrient content of fruits and vegetables consumed in the UK. Our bodies require micronutrients for healthy cell function, immunity, growth, and metabolism,³ and a lack of even just one can have wide-reaching effects.

Furthermore, the lack of nutrient balance in our diets turns on our hunger hormones as a survival mechanism, forcing us to keep eating in an attempt to get more vitamins and minerals into our bodies. When we overeat empty calories, we become overfed and undernourished.³

Strategies to replenish missing nutrients

Increase overall intake of fruit and veg
Not only are we are losing the micronutrient content in our fresh foods, but we are eating less of them too. Much of our daily intake of fruit and vegetables has been replaced with processed foods, offering little nutritional value. What we can aim to do, is make sure that our fruit and veg intake is high enough to compensate for the reduction in nutritional value.

Go organic
The key to healthy produce is healthy soil and an abundance of micronutrients can be found in foods grown naturally and organically on productive soils. Although the data is mixed, one study showed that organic produce averaged higher in calcium, iron, magnesium and zinc.⁴ Another review showed higher mean percentage differences in micronutrient content in organic versus conventional.⁶

Organic and biodynamic farming methods are also likely to promote colonies of soil organisms because of the avoidance of artificial fertilisers and pesticides, boosting nutrient absorption. They also aim to rotate crops to avoid monoculture. Organic plants, grown without pesticides, also need to protect themselves, and therefore produce higher levels of flavonoids and carotenoids.

Organic foods however often come with an increased price. You can find further information in our blog ‘Optimal Health on a Budget’.

Consider supplementation
Supplementing with a multivitamin and mineral is a viable strategy and potential solution to deliver micronutrients that are increasingly diminishing from our food. Wholefood and Food State supplements are often best as they contain vitamins and minerals complete with the associated food factors and other phytonutrients with which they occur in wholefoods. This ensures these are recognisable as food by the human body and optimally utilised.

Eat local and seasonal
Locally grown produce often retains more nutrients as it hasn’t been subjected to transportation and storage. So, even though we may eat a variety of fruits and vegetables all year round, the best time to eat them is when they can be bought shortly after harvest. Seasonally fresh produce is picked when it is fully developed at the peak of the season – this means that it is both fresh and nutritious.

Other considerations

Preparation/cooking
The way we cook our food has an effect on the amount of nutrients it retains so be mindful of the cooking techniques you are using. For example, a large number of micronutrients can be lost from vegetables when they are boiled in water. Switch to steaming to minimise nutrient loss. If you do prefer to boil your vegetables, save the nutrient-rich cooking water to add to soups and sauces.

Improve digestive health
There are a host of modern-day factors that can hinder our ability to absorb the nutrients in our food. To absorb nutrients our digestive system must be working adequately; if the health of our gut is sub-optimal then this is compromised. Chewing our food slowly, sufficient levels of hydrochloric acid and digestive enzymes, plenty of beneficial gut bacteria and healthy cell integrity of the gut are all essential for optimal nutrient absorption.

Lifestyle factors
Certain lifestyle factors such as smoking, high levels of stress, excessive alcohol intake, medications, and poor sleep may all give rise to extra nutrient needs.

Although there is ample evidence that the nutrient levels in our fresh foods are diminishing, being mindful of this and taking steps to increase our micronutrient status can help to safeguard against many of the impacts of micronutrient depletion.

If you have questions regarding the topics that have been raised, or any other health matters, please do contact our team of Nutritional Therapists at nutrition@cytoplan.co.uk or 01684 310099. You can find more nutrition advice resources here.

References:

1. National Diet and Nutrition Survey – GOV.UK. (Accessed: May 27, 2022).

2. Mayer, A. M. B., Trenchard, L., & Rayns, F. (2022). Historical changes in the mineral content of fruit and vegetables in the UK from 1940 to 2019: a concern for human nutrition and agriculture. International Journal of Food Sciences and Nutrition, 73(3), 315–326.

3. The American Epidemic of Micronutrient-Related Malnutrition (drkarafitzgerald.com)

4. Organic foods contain higher levels of certain nutrients, lower levels of pesticides, and may provide health benefits for the consumer – PubMed (2010).

5. Scheelbeek, P.F.D. et al. (2020) “UK’s fruit and vegetable supply increasingly dependent on imports from climate vulnerable producing countries,” Nature food, 1(11), p. 705. doi:10.1038/S43016-020-00179-4.

6. Hunter, D. et al. (2011) “Evaluation of the micronutrient composition of plant foods produced by organic and conventional agricultural methods,” Critical Reviews in Food Science and Nutrition, 51(6), pp. 571–582. doi:10.1080/10408391003721701.

7. Mansfield, P. (2000) The State of our Food. Geest Print, Spalding.

8. NYBG.org: Hidden Partners: Mycorrhizal Fungi and Plants. (Accessed: May 30, 2022).

9. Helander, M. et al. (2018) “Decreases mycorrhizal colonization and affects plant-soil feedback,” Science of the Total Environment, 642, pp. 285–291. doi:10.1016/J.SCITOTENV.2018.05.377.

10. Svenningsen, N.B. et al. (2018) “Suppression of the activity of arbuscular mycorrhizal fungi by the soil microbiota,” The ISME Journal 2018 12:5, 12(5), pp. 1296–1307. doi:10.1038/s41396-018-0059-3.

11. (PDF) Impact of intensive agriculture on arbuscular mycorrhizal assemblages and CO2 flux partitioning in a Mediterranean peatland (no date). (Accessed: May 30, 2022).

12. Corkidi, L. et al. (2002) “Nitrogen fertilization alters the functioning of arbuscular mycorrhizas at two semiarid grasslands,” Plant and Soil, 240(2), pp. 299–310. doi:10.1023/A:1015792204633.

13. Davis, D.R. (2009) “Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence?,” HortScience, 44(1), pp. 15–19. doi:10.21273/HORTSCI.44.1.15.

Last updated on 30th August 2022 by cytoffice