Cereal growers may have reasons to grow organically instead of using 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 are found at similar levels in field crops grown under different management programs.
“These data suggest that we cannot clearly say that manure or organic systems are more nutritious than conventional systems,” said Andrew Smith, chief operating officer of the Organic Agriculture Research Center in Kutztown, in Pennsylvania.
The tests looked at calcium, iron, vitamin K, magnesium, zinc, vitamin B6 and protein, which represent the main nutrients deficient in the typical diet, in the United States and around the world.
There was no need to focus on the nutrients that people typically consume in sufficient amounts, Smith said. Even though these nutrients are deficient in crops, this lack does not substantially affect human health.
But to produce the nutrients humans could bear to eat in greater amounts, Smith said he couldn’t declare one growing system to be definitely better than another.
“Unfortunately, we don’t show a correlation between soil health and plant health,” Smith said.
In corn, calcium and zinc were higher in conventional systems than in organic systems, but this may be because these plantations used different varieties.
“We don’t know why we are seeing this,” Smith said. ” We did not expect that. “
Rodale’s work responded to concerns, widely covered by the media, that crops have lost their nutritional quality in recent decades.
“Around 2000 is where we got alarmed,” Smith said. “Data has been published citing a nutritional decline in our diets, especially minerals.”
Not everyone thinks the alarm clock is in order.
In a 2016 study, Canadian government researcher Robin Marles said changes in nutrition may be the result of strain selection, not soil depletion. Marles also said the apparently large fluctuations in nutrients are within normal variations and likely have no significant effects on the health of consumers.
Rodale recorded the soil health benefits of organic practices in his 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 natural to see if soil health translated into human health.
“We wanted to see if there is a link between soil degradation and the decrease in nutrients in our food,” Smith said.
Philip Gruber contributed reporting.