Organic foods

Health effects of organic vs conventional foods

Organic food is grown without using synthetic fertilizers, chemical pesticides and insecticides, growth hormones, or antibiotics. It cannot be irradiated, contain genetically engineered organisms or genetically modified organisms, and cannot be grown using sewage sludge fertilizer.

Researchers at Stanford University, in California, reviewed the evidence that farming by these criteria is better than conventional methods.

First, the details.

  • 17 studies in humans and 223 studies of nutrient and contaminant levels in foods were reviewed.
  • 2 independent investigators extracted data on study methods, health outcomes, and nutrient and contaminant levels.

And, the results.

  • Nutrient levels
    • No clinically meaningful differences in blood, urine, breast milk, and semen in adults
  • Allergenicity
    • In 3 human studies there were no significant differences in eczema, wheeze, atopic sensitization, or symptomatic Campylobacter infection
      • Campylobacter bacteria, is transmitted in contaminated food or water and may infect the intestines causing diarrhea, fever, and cramps.
  • Urinary pesticide levels
    • In 2 studies there were significantly lower levels in children consuming organic vs conventional diets.
  • Contaminated food
    • Variable except for phosphorus levels, which were statistically but not clinically significantly higher in organic vs conventional produce
  • Risk for contamination with detectable pesticide residue
    • Lower among organic than conventional produce
    • But differences in risk for exceeding maximum allowed limits were small.
  • Bacterial contamination risk
    • No difference in Escherichia coli contamination risk between organic and conventional produce
      • E. coli come from defecation, heavy rain runoff, and contaminated food processing equipment — wash all fruits and veggies before eating them.
    • Bacterial contamination of retail chicken and pork was common but unrelated to farming method.
    • The risk for isolating bacteria resistant to 3 or more antibiotics was higher in conventional than in organic chicken and pork.
  • Studies varied in design and implementation, and were limited in number.
  • Publication bias may have been present, according to the authors.

The bottom line?

The authors concluded, “The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.”

The positive news is that organics are a little bit less likely to contain pesticide residues, and less likely to contain bacteria resistant to antibiotics vs conventional alternatives.

The trend towards organic products is documented. Today, more than 55% of Americans have tried organic foods.

Many consumers purchase organic foods because of the perceived health and nutrition benefits of organic products. A survey by Whole Foods Market 2005 lists the main reasons consumers purchase organic foods. I’ve added whether these reasons are supported by the research as presented in this study.

  • Avoidance of pesticides (70%): not supported
  • Freshness (68%): not addressed in this study
  • Health and nutrition (67%): not supported
  • Avoid genetically modified foods (55%): a regulatory requirement for organic labeling

Consumers pay a 10% to 40% price premium for organic products.

9/4/12 12:00 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.