What’s Behind the Invisible Decline in Nutrient Density?
Nutrient density, functionally, describes higher levels of nutrients and beneficial secondary plant metabolites per unit of volume. Nutrient dense food is virtually the opposite of ‘empty calories’.
There are two really important points to begin with:
- “Nutrient density” is a continuum, a sliding scale from very low to very high
- Nutrients are not inherent characteristics of food, they accumulate.
As the Bionutrient Food Association states, “The problem is, we now live in a world where natural foods, can be nutrient poor. Even organic and local foods can be low in nutrition, depending on the growing practices, season and seed.”
The speed of change we’re experiencing in the world around us is both breathtaking and frightening, and understanding how this is effecting human health is a major challenge for the twenty-first century (1). Over the past 60 years there have been fundamental changes in both the quality and quantity of food (2).
Some experts in the field have stated that our food now has less than one-third of the nutrient density it had pre-World War II (3) and in many parts of the world food looks and tastes radically different to what it did just a few generations ago. This is the first indication that food is less nutritious than it used to be.
When you also factor in the ecological and agricultural changes that have occurred in the past century and that the world has lost a third of its high-quality food-producing land due to erosion or pollution in the past 40 years (4) it becomes clear that nutrient density is under threat (5,6).
Given that nutrient availability is primarily determined by the output of foods produced from agricultural systems, this is where both the problems and solutions lie.
To put it simply, if these agricultural systems fail to provide enough diversity and quantity to satisfy all of the nutrients essential to human health, people will suffer and societies will deteriorate (7).
Top Causes of Nutrient Declines in Food
- Soil health decline; in large part due to a loss in microbial life
- The widespread and increased use of agrochemicals, such as pesticides and synthetic fertilisers
- Dramatic losses in global biodiversity
- Increased use of modern high-yield, genetically modified varieties of crops and animal breeds
- ‘Nutrient dilution’ from increased yields
- Food processing, preparation and storage
- Declines in seasonal, local eating coupled with a more global food system and increased food miles
- Elevated atmospheric CO2
Many of these drivers have been suggested as being unintended consequences of the Green Revolution (8), and all of them impact food quality in different measures and in different ways.
Prof. Carlo Leifert from Southern Cross University, Australia who heads up the Centre for Organics Research says, “What our research shows, is that almost every input that we’ve used in large quantities through the so called Green Revolution has been shown to have a negative impact on our food quality” (9).
What does the data say about nutrient decline over time?
As with almost everything in nutrition — there is a mixed bag of evidence. Meaning, there is evidence showing no meaningful declines (10), evidence showing mixed results in regards to nutrient declines, and evidence showing significant declines.
One Australian report prepared by Food Standards Australia New Zealand (FSANZ) compared the levels of phosphorus, sodium, calcium, magnesium, iron and zinc in 44 types of Melbourne-purchased fruits and vegetables in 2000/2001 to the same items purchased in Sydney circa 1981–1985. They found no significant or consistent differences in overall patterns of minerals over time.
However, as the authors themselves point out, the samples were collected in different locations, sometimes at different times of the year, possibly at different stages of ripeness, in many cases were different varieties, and older analyses were conducted using a less sensitive analytical technique (11).
Another study (12) concluded that although historical data (from various countries) shows declines in mineral nutrients of vegetables, fruits and grains; comparisons of food composition data published decades apart are not reliable. They argue that the ‘nutrient dilution’ that has occurred is small, and is outweighed by the benefits of increased yield. In other words, they argue that although the quality of food may have dropped, the increase in quantity apparently makes up for these losses.
I disagree with the view that quantity is more important than quality. Nearly half of all countries worldwide now experience serious levels of both under-nutrition and obesity, and around a billion people are suffering from “hidden hunger”, where important micro-nutrients are missing from their diets (13).
At least half of children worldwide ages 6 months to 5 years suffer from one or more micro-nutrient deficiency, and globally more than 2 billion people are affected 14. Deficiencies in micro-nutrients such as iron, iodine, vitamin A, folate and zinc can have devastating consequences; and these deficiencies occur in both developing and developed countries.
One well cited study by Donald Davis found that the average nutrient content of most vegetables and fruits have declined dramatically over the past 50–70 years. His team reviewed historical nutrient content data for 43 crops between 1950 and 1999 and found that all 43 foods showed varying levels of decline for 6 nutrients — including protein, calcium, phosphorus, iron, riboflavin, and vitamin C (15).
Although analysis methods have since been questioned (12), further analysis has confirmed statistically significant nutritional losses for copper, calcium, iron and magnesium.
Certain minerals have had extra attention given to them, like magnesium, which has been steadily declining in just about every food tested, from cheese to vegetables (2,16). The magnesium content of wheat has dropped by almost 20% since the 1960s (16) and comparisons of the magnesium content listings in food composition tables (from the U.K., USA and Canada) also show a historical decrease (between 7–35%) in the magnesium content of grains, fruits and vegetables.
So how much can we rely on reference charts in regards to nutritional data?
Not a lot, because it’s a seriously inexact science. To explain, let’s stay with magnesium for a moment. According to Australian nutrient reference charts, to get exactly 78mg of Magnesium, one should eat ½ cup of boiled spinach (17).
In this example, the magnesium content of spinach was sourced from the analysis of 5 spinach samples, taken from Sydney supermarkets between 1983 and 1984. Not only is this data 36 years old, but there is no information other than the geographic location. We don’t know what types of spinach were sampled, how biologically rich the soil was, or what agricultural practices were employed.
Even if it was an exact science and there was 78mg of magnesium in each and every ½ cup of boiled spinach, this doesn’t factor in post-harvest operations like sterilisation, heating/freezing, dispersing, packaging, storage, distribution and transport (all of which effect micro-nutrient levels considerably).
Data from government food composition tables represent snapshots of nutrient compositions for foods at a particular time and they can offer some indication about the nutrient content of foods, but they have many flaws and their accuracy is far from reliable.
Instead, nutrients should be reflected as a range, as is done in other parts of the world, like Germany where for instance in potatoes, the potassium ‘range’ is 340–600 mg/100 g (11). Other research has shown an up to tenfold variation in levels of some minerals (e.g. potassium in carrots) between purchases made at different times and places in countries such as Sweden (18).
Changes in the genetic varieties of crops on the market over time, large ranges of variation in content of different nutrients from variety to variety of the same crop, and differences in geographic origin, season, degree of ripeness, sample sizes, sampling methods, analytical methods and statistical methods (12) all impact upon the numbers we see in those charts.
The team from the Bionutrient Food Association (USA) has done some amazing work in this field. They’ve analysed foods from 7 states, 50 unique stores and 68 farms and gardens (19). From 829 samples, they found there was significant variation (up to 200:1) in antioxidants, polyphenols, and minerals in foods such as carrots and spinach.
This demonstrates how much more work needs to be done in this space to understand what aspects actually guarantee nutrient dense food, and that there is currently tremendous variability.
The Elephant in the Room — Soil Biology
Just as beneficial bacteria help to make nutrients available to us in our digestive tracts, soil organisms are responsible for making nutrients biologically available to plants. In fact, root symbionts (microorganisms) have profound capacity to increase the nutritional quality of food — on just about all levels — from minerals, to secondary plant metabolites, to beneficial fatty acids (20).
When organisms like mycorrhizal fungi search for nutrients, they act as intelligent filters. As they move through the soil, they are actively seeking out, selecting, and absorbing essential nutrients are the right concentrations, in the right forms, in the right ratios, in the right balances (3). Mind blowing really!
It’s been estimated that about two-thirds of agricultural land in Australia is suffering from acidification, contamination, depletion of nutrients and organic matter, and/or salinisation (21); and the growing industrialisation of agriculture has resulted in reduced soil biodiversity (21,22).
In industrially farmed soils, organisms like mycorrhizal fungi are killed off by tillage, fungicides and other chemicals, and there is no intelligent filter to determine what balance of nutrients is appropriate for sustaining life (3, 23).
The cocktail of ‘biocide’ chemicals that plants are given (from fungicides, herbicides, pesticides, fertilisers, etc.) not only diminish the uptake of beneficial nutrients, but also make less desirable substances, such as nitrates, phosphates, lead, arsenic and chlorine more available (3). So, not only do we have less nutritious food, we have a greater likelihood of toxicity and a system that is reliant on chemical inputs for production.
The nutritional integrity of foods grown in a setting where nutrients can be taken up from the soil in this selective, intelligent way is fundamentally different from the nutritional integrity of food that has been produced without this intelligent filter (3), and the soil management practices that farms employ are a key determinant of nutrient density (21).
Soil Mineral Analysis — An Incomplete Picture
Although some studies that have compared archived soil sample have shown that soil mineral content has not declined in locations cultivated intensively with various fertilizer treatments (12); there is a problem with this argument. The problem is… soil mineral analysis only gives us part of the picture.
John Kempf, a leading expert in the field of biological and regenerative farming, says;
“Historically, the assumption has been to use soil analysis, and balance the minerals according to the soil test and that would grow a very healthy crop. If the soil test is low in calcium, we add more calcium. If it’s low in phosphorous, we add more phosphorous. And that is not incorrect, but it is incomplete. It’s possible to have a perfectly balanced soil test and still have a crop that is extremely unhealthy.” (20)
This is not dissimilar to what we see with poorly interpreted general pathology testing in the human health space. For example, low serum calcium is not a reflection of dietary intake or bone levels of calcium. It’s not that the serum calcium (or magnesium for that matter) results are incorrect, they are just incomplete and we need to be careful with drawing simple conclusions.
The Infamous Glyphosate
Following its successful commercial introduction in 1974 in the USA, glyphosate has become the dominant herbicide used worldwide. It is used on genetically modified glyphosate-resistant crops, as well as traditional grain crops, trees, orchards, groves, waterways and urban areas (such as parks and streets). In other words, it’s everywhere. It’s been estimated that we’re using over 2 billion kilograms of glyphosate worldwide right now (24).
In 2015, the World Health Organisation reclassified glyphosate as “probably carcinogenic to humans”, and since then, there have been over 1000 research papers published on the potential side effects. In animal data (and some human clinical trials), glyphosate has been linked to cancer, kidney damage, mental conditions (such as ADHD, autism, Alzheimer’s disease, and Parkinson’s disease), non-alcoholic fatty liver disease, miscarriages, infertility and dermatological conditions (26).
Don Huber is a Professor Emeritus of Plant Pathology with over 55 years in research and teaching on plant pathology with special emphasis on the ecology of soil borne pathogens, host-parasite interactions and nutrient-disease interactions. In my view, he’s the ‘glyphosate guru’ (25) and when he has something to say about glyphosate, I listen.
Among other things, he’s found that;
- Glyphosate, even in very small amounts, is a powerful chelator of calcium, magnesium, iron, manganese, copper, zinc, cobalt and nickel; reducing plant uptakes of some of these micro-nutrients by as much as 80%. When you take one micro-nutrient out, there’s a domino effect. It makes all of them less efficient.
- Glyphosate is also toxic to microbes needed to make nutrients available and facilitate their uptake and activity. This includes its antibiotic activity against mycorrhizae that facilitate uptake of phosphorus, manganese and zinc as well as the many organisms involved in biological nutrient cycles in soil and our gut microbiomes.
- GMO crops such as Roundup Ready alfalfa have been shown to have lower nutrient level (of 11 minerals) when compared to non-GMO Roundup ready crops. (26)
As pervasive and disastrous glyphosate is (against all forms of life), it’s sadly not considered to be the most destructive biocide and is rarely used as a standalone. Although the collective impacts of industrial pesticides, insectides and herbicides are hard to quantify; the long-term impacts on human health, food quality, precious ecological systems and Mother Nature are staggering and there’s never been a more urgent time to transition to regenerative, ecologically friendly practices as alternative solutions.
Regenerative practices use models that don’t compromise on quality (nutrient density) whilst maintaining quantity (yield); reduce chemical use and enhance biodiversity. In doing these things, there is an increase the populations of rhizospheric microbes, boosting both nutrition and profit (13,27).
What about the all-important Phytochemicals?
Historically, researchers have focused on more measurable parts of foods, such as the vitamins and minerals, missing a HUGE part of the story — secondary plant metabolites (SPMs). Also known as phytochemicals, these metabolites really are the nutritional rock stars.
Epidemiological studies echo this, suggesting that diets rich in phytochemicals can reduce the risk of cardiovascular disease, stroke, diabetes, some cancers, rheumatoid arthritis and neurodegenerative diseases (27).
Familiar examples of SPMs include resveratrol in grapes, sulforaphane in brassicas, curcumin in turmeric, catechins in green tea and allicin in garlic. Not only are they good for us (in healthy doses), they are the foundation of a plant’s immunity.
Plants produce a bewildering arsenal of phytochemicals (27), and the production of plant secondary metabolites is triggered by a thriving microbial community. By enhancing the nutritional profile and soil biology of the plant, the natural production of secondary metabolites can significantly reduce the need for and use of pesticides, further protecting the precious microbes that the plant relies on.
Unfortunately, these phytochemical rock-stars are heavily influenced by modern industrial practices. Professor Carlo Leifert has found that the use of Nitrogen-based synthetic fertilisers is correlated with low secondary metabolite production; with over 60% higher flavonoid levels in organically produced foods. This echoes other data which showed that nitrogen application and the use of NPK fertilisers can reduce the total phenol, total flavonoid and antioxidant activity (28).
Plant breeding and a shift to modern varieties of seeds also have an impact on SPMs.
In the process of making modern varieties of fruits and vegetables more palatable, we have selected against many of the beneficial phytonutrients that have a sour, acrid, bitter or astringent taste (21,29).
Ancient varieties of plants can now be measured in regards to nutrient density, showing fascinating results. For example, varieties of ancient soybeans have five times more omega-3s than modern varieties; wild dandelion greens have seven times more phytonutrients than spinach; and an ancient varieties of apples that have one hundred times more phytonutrients than the Golden Delicious (29).
Further to these issues, commonly used chemicals can also impact negatively upon SPMs. For example, applications of glyphosate to coca plants can have dramatic effects on the quantity and quality of alkaloids produced by surviving or subsequent leaves (30).
Eating food that has been grown in biologically rich soil is a sure fire way to increase the nutrient density of your diet; as is eating meat that has been raised using soil-enhancing regenerative practices, which brings me to my next point…
Not all meat is created equally.
Up until now, this entire discussion has centered on plants, but it is not only humans whose food is becoming less nutritious. Herein lies another big question; what happens to the nutritional profile of meat if the animals food (i.e. natural pastures) is less nutritious, or isn’t natural pasture at all?
Emeritus Professor Fred Provenza has written extensively about this topic. In his fascinating paper, published in Frontiers of Nutrition earlier this year, he states that:
“Circumstantial evidence supports the hypothesis that phytochemical richness of herbivore diets enhances biochemical richness of meat and dairy, which is linked with human and environmental health. Among many roles they play in health, phytochemicals in herbivore diets protect meat and dairy from protein oxidation and lipid peroxidation that cause low-grade systemic inflammation implicated in heart disease and cancer in humans.” (31).
In other words, our health is linked to the diets of animals such as cattle, through the chemical characteristics of the forages (or lack thereof) that they eat. If they’re eating nutritious, phytochemically rich forage, we benefit, because diverse plant communities act as nutrition centers and pharmacies for animals, ultimately enabling health (for them and us) (31).
The Impact of Climate Change
Elevated carbon dioxide (CO2) in the atmosphere has the potential to lead to less nutritious food in several ways, many of which haven’t been fully teased out just yet and remain controversial.
One possible mechanism is the observed increases photosynthesis in plants exposed to higher levels of CO2 (29). Although this increases the rate of growth, the higher carbohydrate (glucose) accumulation leaves less room for other crucial nutrients like protein and minerals (such as zinc and iron).
Global warming also threatens soil biodiversity, and slight changes in temperatures and moisture can have profound impacts on soil, altering the composition of soil life and the types of plants that can grow (23).
The Issue of Globalisation and Ultra-Processing
The entire discussion surrounding nutrient declines over time (and associated health impacts) is based on three major assumptions;
1. That we are eating Australian grown food,
2. That the food we’re eating is in season and is fresh,
3. That we’re eating whole foods.
The amount of processing that happens post-harvesting also cannot be overlooked. Before a food gets to your mouth, it may have undergone a range of post-harvest operations, including cleaning/sterilising, irradiation, milling, separating, mixing, drying/hydrating, heating, dispersing, packaging, storage, distribution and transport (21) . Remember, the more we mess with the primary food, the lower the overall nutrient content.
Finally, given that around 1/3 of what Australian’s eat is actually ultra-processed, deficiencies don’t just reflect “poor soil health” and nutrient declines, they reflect our collective consumption of hollow foods and the desire eat foods that aren’t local or seasonal.
My Sense of it all…
I’m of course not suggesting that there are NO nutrients in the soil or our food, or that we should all be taking copious amounts of supplements. I certainly don’t.
Modern wholefoods can of course still be nutritionally valuable, but the variations are huge and for the reasons I’ve outlined, the nutritional deficits can be significant.
We can offset some of the issues we face with nutrient density by choosing to eat more FRESH, LOCAL and SEASONAL fruits and vegetable to fill any nutritional deficits, and/or grow more foods that have a higher nutrient density to begin with (such as wild greens, heirloom varieties of fruit and vegetables and animals raised on natural pastures).
There are so many solutions which are already being implemented by a growing number of producers, which in my view is arguably the most important work that is being done in the nutrition space. When farmers improve ecological health and microbial life, the health of plants (and animals) responds in amazing ways, with measurable increases in nutrients, lipids and the medicinal secondary plant metabolites (6,20).
We need to recognise the true cost of cheap, low-quality foods; and collectively change the paradigms around how we grow, purchase and consume food.
Although a global food revolution is required, the next important step for consumers is to simply connect with and support the people who are nourishing our soils, regenerating our land and growing our food, because the answers to our nutritional problems lie in their paddocks.
Until next time,
Stacey.
References
1. Paseka RE, Bratt AR, MacNeill KL, Burian A, See CR. Elemental Ratios Link Environmental Change and Human Health. Front Ecol Evol. 2019;7:378.
2. Thomas D. The Mineral Depletion of Foods Available to US as A Nation (1940–2002) — A Review of the 6th Edition of McCance and Widdowson <sup/>. Nutr Health. 2007;19(1–2):21–55.
3. Pershouse D. The Ecology of Care; Medicine, Agriculture, Money and the Quiet Power of Human and Microbial Communities. Mycelium Books; 2016.
4. Milman O. Earth has lost a third of arable land in past 40 years, scientists say | Environment | The Guardian. https://www.theguardian.com/environment/2015/dec/02/arable-land-soil-food-security-shortage. Published December 2, 2015. Accessed October 15, 2019.
5. DiNicolantonio JJ, O’Keefe JH, Wilson W. Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis. Open Heart. 2018;5(1):e000668.
6. Shiva VD. Food, Farming and Health. Acres USA, Colorado; 2017.
7. Welch RossM. The impact of mineral nutrients in food crops on global human health. Plant Soil. 2002;247(1):83–90.
8. Public Seminars — Southern Cross University. https://www.scu.edu.au/centre-for-organics-research/public-seminars/. Published 2018. Accessed October 15, 2019.
9. Professor Carlo Leifert. Organic Farming Research. Presented at the: May 2018; Southern Cross University. https://www.scu.edu.au/centre-for-organics-research/public-seminars/.
10. James W. Lyne and Phillip Barak. Are Depleted Soils Causing a Reduction in the Mineral Content Of Food Crops? https://soils.wisc.edu/facstaff/barak/poster_gallery/minneapolis2000a/. Published November 2000. Accessed October 10, 2019.
11. Cunningham JH, Milligan G, Trevisan L. Minerals in Australian fruits and vegetables. :16.
12. Marles RJ. Mineral nutrient composition of vegetables, fruits and grains: The context of reports of apparent historical declines | Elsevier Enhanced Reader.
13. García-Mier L, Guevara-González RG, Mondragón-Olguín VM, Verduzco-Cuellar B del R, Torres-Pacheco I. Agriculture and Bioactives: Achieving Both Crop Yield and Phytochemicals. Int J Mol Sci. 2013;14(2):4203–4222.
14. Micronutrient Initiative, ed. Investing in the Future: A United Call to Action on Vitamin and Mineral Deficiencies: Global Report, 2009. [New Delhi: Micronutrient Initiative; 2009.
15. Davis DR. Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence? HortScience. 2009;44(1):15–19. doi:10.21273/HORTSCI.44.1.15
16. Guo W, Nazim H, Liang Z, Yang D. Magnesium deficiency in plants: An urgent problem. Crop J. 2016;4(2):83–91.
17. Australia H. Foods high in magnesium. https://www.healthdirect.gov.au/foods-high-in-magnesium. Published July 30, 2019. Accessed October 24, 2019.
18. Torelm I, Danielsson R. Variations in Major Nutrients and Minerals in Swedish Foods: A Multivariate, Multifactorial Approach to the Effects of Season, Region, and Chain. J Food Compos Anal. 1998;11(1):11–31.
19. RFC 2018 Final Report. Real Food Campaign Lab. February 2019. https://lab.realfoodcampaign.org/reports/rfc-2018-final-report/. Accessed October 4, 2019.
20. Kempf J. Advancing Eco Agriculture | Regenerative Farming | Managing Nutrition. advancing-eco. https://www.advancingecoag.com/managing-nutritional-integrity. Published 2019. Accessed September 30, 2019.
21. Blum WEH, Zechmeister-Boltenstern S, Keiblinger KM. Does Soil Contribute to the Human Gut Microbiome? Microorganisms. 2019;7(9):287.
22. Bender SF, Wagg C, van der Heijden MGA. An Underground Revolution: Biodiversity and Soil Ecological Engineering for Agricultural Sustainability. Trends Ecol Evol. 2016;31(6):440–452.
23. Robbins J. Opinion | The Hidden World of Soil Under Our Feet. The New York Times. https://www.nytimes.com/2013/05/12/opinion/sunday/the-hidden-world-of-soil-under-our-feet.html. Published May 11, 2013. Accessed October 30, 2019.
24. Dr. Zach Bush. Soil Health, Intercellular Communication and Their Effects on Human Health: A Special Interview With Dr. Zach Bush By Dr. Joseph Mercola. January 2018. https://bsahely.com/2018/01/25/soil-health-intercellular-communication-and-their-effects-on-human-health-a-special-interview-with-dr-zach-bush-by-dr-joseph-mercola/.
25. Stephen Burns. Glyphosate use in the spotlight at Wodonga | The Land. https://www.theland.com.au/story/5981064/concerns-around-glyphosate-attract-wider-audience/. Published March 30, 2019. Accessed October 29, 2019.
26. Graze Magazine. The problem with Roundup Ready food | Graze magazine. https://www.grazeonline.com/problemroundup. Published March 2011. Accessed October 29, 2019.
27. Murugaiyah V, Mattson MP. Neurohormetic phytochemicals: An evolutionary–bioenergetic perspective. Neurochem Int. 2015;89:271–280.
28. Allahdadi M, Farzane P. Influence of different levels of nitrogen fertilizer on some phytochemical characteristics of artichoke (Cynara scolymus L.) leaves. :7.
29. Little, Amanda. The Fate of Food- What We’ll Eat in a Bigger, Hotter, Smarter World. One World Publications, London, England.; 2019.
30. Apparent Effects of Glyphosate on Alkaloid Production in Coca Plants Grown in Colombia — Casale — 2007 — Journal of Forensic Sciences — Wiley Online Library. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1556-4029.2007.00418.x. Accessed September 30, 2019.
31. Provenza FD, Kronberg SL, Gregorini P. Is Grassfed Meat and Dairy Better for Human and Environmental Health? Front Nutr. 2019;6:26.
