Grain producers may have reasons to grow organically instead of with conventional methods, but the nutritional content of their harvest is not one of them.
Experiments at the Rodale Institute show that key nutrients that are often deficient in human diets occur at similar levels in field crops grown under different management programs.
“This data is suggesting that we can’t clearly say that the manure or organic systems are more nutritious than the conventional systems,” said Andrew Smith, chief operating officer of the organic farming research center in Kutztown, Pennsylvania.
The tests looked at calcium, iron, vitamin K, magnesium, zinc, vitamin B6, and protein, which represent the top nutrients deficient in the typical diet, both in America and globally.
There was no need to focus on nutrients that people generally consume in sufficient quantities, Smith said. Even if those nutrients are deficient in the crops, that shortfall isn’t substantially affecting human health.
But for producing the nutrients humans could stand to eat in greater quantities, Smith said he can’t declare one growing system definitively better than another.
“Unfortunately, we are not showing a correlation between soil health and plant health,” Smith said.
In corn, calcium and zinc were higher in conventional systems than in organic, but that may have been because those plantings used different varieties.
“We’re not sure why we’re seeing that,” Smith said. “We weren’t expecting it.”
Rodale’s work addressed concerns, widely covered in the media, that crops have been losing nutritional quality over recent decades.
“Around 2000 is where we became alarmed,” Smith said. “Data came out citing a nutritional decline in our food, particularly in minerals.”
Not everyone believes alarm is in order.
In a 2016 study, Canadian government researcher Robin Marles said that changes in nutrition may be a result of variety selection, not soil depletion. Marles also said that seemingly large fluctuations in nutrients are within normal variations and unlikely to have significant effects on consumers’ health.
Rodale has recorded soil health advantages from organic practices in its farming systems trial, which has been running for 40 years and includes tilled and no-till plots with organic and conventional pest management.
It was only natural to see if soil health translated to human health.
“We wanted to see if there’s a link between degradation of soil and the decreased nutrients in our foods,” Smith said.
Philip Gruber contributed reporting.