by Sheryl Karas M.A., CRARS staff
According to multiple studies in several countries, the nutrient density of our food has fallen tremendously in the last 50-70 years. The most famous study, done by Donald Davis of the Biochemical Institute at the University of Texas in Austin, compared data gathered by the USDA in 1950 and 1999 on the nutrient content of 43 fruit and vegetable crops and found that six out of 13 nutrients studied had declined by 9-38%. The nutrients affected were phosphorous, iron, calcium, protein, riboflavin, and ascorbic acid (a precursor of vitamin C). Similar or even more disturbing results were found in studies done in Great Britain and Australia (PDF), and declines increased for the longest time periods studied.
What this means is that it is more difficult to get the same level of nutrition from the food we eat than was enjoyed by our grandparents. The impact on this for poor people is of particular concern. According to a report by the Global Hunger Index, two billion people suffer from “hidden hunger,” getting enough calories but not enough nutrients for good health and development. The impact is greatest on young children and pregnant women and can include stunted growth, mental impairment, and lowered immune system function. In the United States, nutritionists decry the fact that it is now possible to be obese and yet suffer health effects from malnutrition.
Of course, these results are not the result of just nutrient density scores alone—food choice and availability has a lot to do with it. But the declines are of great concern because how does it relate to how our food is grown, and how can we address it? Advances in modern agriculture (heavy tillage, fertilizers, pesticides and herbicides, etc.) make more food available than ever before. The USDA estimates that the average farmer in the United States is able to feed 155 people today, compared to 19 people in 1940. But if the nutritional quality of the food grown has declined, we need to determine why so we can make informed choices for the future.
Significant evidence shows that the higher yields we are achieving in our fields can be correlated with reductions in nutrient density in the plants. And numerous studies point to the idea that decline in soil quality due to certain agricultural practices might be to blame. Certainly, growing more plants per acre takes more nutrients out of the soil if those nutrients are not replaced. Of course, that’s what commonly used soil amendments such as phosphorous and nitrogen are supposed to provide.
But soil scientists like Christine Jones are now pointing to studies that show that the problem is not necessarily a lack of fertilizer but rather a disruption in normal biological processes found in nature. She points to studies that show that crops grown in healthy, biologically active soils do not have lower nutrient levels. She believes the problem stems from soil conditions that are not conducive to nutrient uptake. The minerals are present in the soil but are not available to the plants because the soil biology that facilitates this has been disrupted through heavy tillage, leaving the soil bare between plantings, and the application of herbicides, fungicides and chemical fertilizers. She says that in biologically healthy conditions 85 to 90 percent of plant nutrient acquisition is mediated by microbes, and she believes that if today’s crops are less nutrient-dense, practices that harm or kill the soil biology are to blame.
In regenerative agriculture efforts are made to reduce disturbance and nurture the soil biology. Techniques like no-till or low-till farming, the use of biodiverse cover crops, crop rotation, and the use of green manure or livestock integration all support the life of the soil. These practices have been shown to increase soil organic matter, improve water holding capacity, and reduce soil water evaporation. This helps reduce soil erosion and, in time, soil fertility recovers where depleted. It can also have a significant impact on the amount of carbon sequestration possible, which could help combat or mitigate the effects of climate change. What we don’t know is whether and to what degree nutrient density may be affected. More data is also needed to help determine the best practices for effectively converting from conventional to regenerative techniques with the most economic return.
The Center for Regenerative Agriculture at Chico State has recently received a grant through the California State University Agricultural Research Institute (ARI) for a three-year study to investigate the impact of no-till farming practices on soil health, nutrient density and profitability in California organic vegetable production systems. Because weed suppression is a significant concern for farmers thinking about converting to this approach, the study will also compare two kinds of mulch already used by some regenerative farms for this purpose. The research will be conducted at the Organic Vegetable Project (OVP) located at the University Farm. Learn more about it on our website.