Good_Food_Display, Phto by NIH, Public Domain
(Click on the following link to listen to an audio version of this blog … What’s happening to our food?
There are many things about our food that worry us: overly processed ingredients, excessive levels of fats and sugars and salts (often added to trick us into eating more), added palm oils, chemical preservatives and artificial colorings. Recent research into the chemical composition of food, though, suggests that there might also be an on-going, “natural” process that is reducing the quality of foods we eat.
Quality of food can be described in many ways. Subjective features (taste, aroma, texture etc.) may be of prime importance to a consumer, but they are very difficult to measure or standardize. Objective features of a food (like number of calories per gram, amount of fiber and levels of macro-and micronutrients) are much easier to quantify and compare. A great deal of data about the nutrient composition of our foods has been gathered throughout the 20th and 21st Centuries and is available in several large, governmental data bases.
Fresh_cut_fruits_and_vegetables. Photo by USDA, Public Domain
One published study (British Food Journal , July 1, 1996) examined the food tables compiled by the government of the United Kingdom (UK). These tables recorded the annual analysis of the mineral content of twenty fruits and twenty vegetables. The paper compared data collected from fruits and vegetables in the 1930’s to the data collected in the 1980’s. In both fruits and vegetables total dry matter decreased and moisture content increased over the fifty year time span. In vegetables, there were significant declines in calcium, magnesium, copper and sodium. In fruits, there were significant declines in magnesium, iron, copper and potassium.
In another paper by the same author as the above, 1996 study, the mineral and micronutrient composition of UK fruits and vegetables from 1940, 1991 and 2019 were examined. This study (published in the International Journal of Food Science and Nutrition (October 15, 2021)) showed that all minerals and nutrients in the fruits and vegetables analyzed decreased in the 80 years between 1940 and 2019 with the exception of phosphorous. In particular, sodium levels declined by 52%, iron levels declined by 50%, copper levels declined by 49% and manganese levels declined by 10%.
Fruit_and_vegetables, National Cancer Institute, Public Domain
A similar study in the United States explored the annual data collected by the U. S. Department of Agriculture on the nutrient composition of 43 types of garden-grown vegetables from 1950 to 1999. This study (published in the Journal of the American College of Nutrition (June 18, 2013)) found significant decreases in the vegetables’ protein, calcium, phosphorus, iron, riboflavin and Vitamin C over the fifty year time period.
The authors of these three studies and a number of reviewers and critics of these papers point out that the information in the government data tables may not have been collected in a consistent manner each year, thus making year to year comparisons very difficult. There was no regularity in the sources for the fruits and vegetables analyzed, no consistency in the sites in which they were grown. Further, the ripeness or age of the fruits and vegetables analyzed was not standardized, and the analytical methods used to evaluate the fruits and vegetables changed over the decades of the data collection.
In spite of these confounding difficulties, the authors of these three papers are adamant that something is happening to our fruits and vegetables. Whatever this process is, it is causing a reduction in the mineral and micronutrient composition of these important foods!
Wheat-flour. Photo by ارون يحيى Wikimedia Commons
Carbohydrates typically make up a much larger percentage of most peoples’ diets than do fruits or vegetables. Wheat and rice, in particular, are major calorie sources for most of the world’s population. Wheat makes up 25% of the average daily caloric intake for people in the United Kingdom, Europe and the United States, and rice makes up just over 29% of the average daily caloric intake for individuals in most Asian countries. It is estimated that half of the world’s population (some four billion people) rely on rice as a staple food. It is also important to note that the poorer the population cohort is within these wheat-dominated and rice-dominated societies, the greater the daily percentage of calories they are likely to take from carbohydrate-based foods.
In 1843, John Bennet Lawes began a study at his estate in Hertfordshire, England in which he examined the effects of different levels of mineral fertilizers and manures on the productivity of grain crops (wheat and barley). Each year, Lawes carefully collected soil samples and mature grain samples from his wheat and barley fields. Lawes’ study continued after his death, and his estate eventually became the Rothamsted Experiment Station (now called Rothamsted Research) one of the world’s premier agricultural research institutions. Scientists at Rothamsted have continued Lawes’ study on his wheat fields and now have 180 years of data (and over 300,000 soil and grain samples) from which they can very closely assess the nutrient and mineral content of the wheat and the soils in which the wheat was grown.
Plaque at Rothamsted, Photo by Yerpo, Wikimedia Commons
Analysis of these samples indicates that between 1845 and 1967 the levels of minerals and micronutrients in the Rothamsted wheat were very stable. After 1968, though, levels of zinc, copper and magnesium began to decline. Analysis of the soil samples, though, showed no decline in any mineral nutrients over the 180 years of the study.
What could be the possible reasons for these very precisely observed declines in the micronutrient composition in the wheat or the apparent declines in micronutrients in the fruits and vegetables?
One hypothesis suggests that the development of new, faster growing, higher yielding varieties of these crops may be causing the changes in nutrient composition. For wheat, these new varieties were part of the “Green Revolution” that radically changed agriculture and substantially increased crop yields starting in the mid-Twentieth Century. Possibly these new varieties of crop plants were more focused on accumulating carbon and biomass than they were on gathering micronutrients.
Wheat_close-up, Photo by user.Bluemoose, Wikimedia Commons
Another suggestion concerned the effect of increased atmospheric carbon dioxide on the growth rates and patterns of these crop plants. Atmospheric carbon dioxide has increased from 316 ppm in 1959 to 424 ppm in 2023! Most plants grow more rapidly at higher carbon dioxide levels, and, because they take in sufficient amounts of carbon dioxide for their photosynthetic metabolism over shorter periods of time, tend to keep the stomata in their leaves closed for longer portions of the day. Keeping the stomata closed reduces transpirational water loss from the plant which then reduces the flow of nutrient-rich soil water into the plants roots. This decline in nutrient uptake may explain the observed decline in micronutrient levels in wheat and also in the fruits and vegetables.
Rice_paddy. Photo by Takeaway. Wikimedia Commons
Experiments conducted on rice have shown similar micronutrient declines when the rice was grown under conditions of higher atmospheric carbon dioxide. On average, both rice and wheat showed 5% reductions in micronutrients when grown at higher (i.e. present day) levels of atmospheric carbon dioxide. In affluent societies, these micronutrient deficiencies are easily made up by dietary supplements or direct enrichment of processed foods. In less affluent societies, though, supplementation or enrichment is not likely to occur, and, as I mentioned earlier in this essay, the less affluent a group of people are, the greater they rely on carbohydrates for their dietary energy. These micronutrient declines in rice and wheat are going to hit poorer societies very hard and very quickly. Worldwide, it is estimated two billion people have diets deficient in micronutrients. This number is expected to grow over the coming decades.
The physical effects of Climate Change are clear to almost everyone. Sea levels will rise and coastal regions will be flooded. Weather patterns will change affecting wild ecosystems and also agroecosystems. Tropical diseases will spread into higher latitudes, and wildfires will become more common and more intense. Some places on Earth will become uninhabitable sending large numbers of people off on quests to find new places to live. The political and social stresses of these climate-triggered mass migrations of people are already being felt in Europe and in the United States.
To underline this ongoing reality of a changing climate, this past year, 2023, was the warmest year in human recorded history. And now, we learn that the higher atmospheric levels of carbon dioxide may even be changing the way plants grow! It may be changing the very essence of our food supply! What next?