Organic foods found to have less toxic cadmium than conventional crops

hothouse lettuce
CC BY 2.0 Ken Hawkins

This summer, a large meta-study published in the British Journal of Nutrition gathered together data from hundreds of studies comparing conventional and organic crops. The authors conclude that organic foods have higher levels of antioxidants and less pesticide residue. They also find that organic crops have half as much of the heavy metal cadmium.

Mark F. McCarty and James J. DiNicolantonio explore the health implications of lowering of one’s exposure to this toxic metal through diet in a commentary also published in the British Journal of Nutrition.

Cadmium accumulates in the body, and high levels are associated with a higher risk of cardiovascular disease and cancer. People with higher levels of cadmium in their urine are also found to have higher total mortality rates. DiNicolantonio and McCarty estimate that lowering exposure to this heavy metal by 50 percent—the amount represented by switching from conventional produce to organic—might lower total mortality by 20 percent.

People may be exposed to cadmium by smoking or occupational hazards, but diet can also be a major source. The toxin can be found in foods that are otherwise considered to be healthy, such as grains, greens and root vegetables. Vegans who consume more of these foods may be at a higher risk, and DiNicolantonio and McCarty cite one study that found vegans do indeed have higher blood concentration of cadmium than omnivores.

Organically grown crops aren’t inherently low in cadmium, but the cadmium level found in plants reflects the makeup of the soil. “The cadmium content is determined by two things,” said DiNicolantonio told TreeHugger. First there’s the soil. “If the soil is more acidic, the plant is more likely to take up cadmium.”

Second, there’s the fertilizer. “It just so happens to be that phosphate fertilizers are used mainly on conventionally grown crops, and basically what happens is that heavy metals are transferred from the phosphate rock into those conventional fertilizers,” said DiNicolantonio. The compost and manure that are used to fertilize organic crops don’t suffer from this kind of heavy metal contamination.

“It’s important to know that we’re not suggesting that conventionally grown foods are not healthy,” said DiNicolantonio. However, he argues that organic crops are safer and healthier.

There has been considerable debate in the scientific community over the comparative health benefits of organic versus conventional crops, and various studies have come to conflicting conclusions. This is in part due to different research methodology and also what nutrients are being considered. DiNicolantonio said a scientific consensus on the issue may not be reached in our lifetime.

Further research may be needed to determine if our bodies can really use the nutrients available in these foods, and if that differs across conventional and organic farming techniques. “How those nutrients are being absorbed in the body and how they are working in the body probably matters a lot more than how much is contained in the actual substance,” he said.

So, should you switch to organic fruits and vegetables? In addition to the environmental benefits of organic farming, there’s no health risk involved in picking organic foods over conventional ones. “What would be the harm of switching from conventionally grown products to organically grown products?” said DiNicolantonio. “I really don’t see one.”

Organic foods found to have less toxic cadmium than conventional crops
Fertilizers used in conventional farming are exposing us to higher levels of this heavy metal.

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