Newsflash: Dietary Study Has Unexpected Results

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Center member Dr. Sheela Sathyanarayana and her colleagues have published the results of an intervention trial that attempted to reduce exposure to endocrine-disrupting phthalates and Bisphenol A (BPA) in the diet. The article was released today in the Journal of Exposure Science and Environmental Epidemiology.

Phthalates and BPA are found in a wide variety of plastic products and contaminants in food. They can harm pregnant women and young children. The researchers wanted to find out if asking families to follow written instructions would lead to reduced exposure to these chemicals, compared to providing a catered diet specially prepared without plastics.

The study took place in summer, 2011 in Seattle. Eligible participants were 2-parent families with at least two 4-8 year-old children. Ten families with a total of 40 individuals were enrolled. The families were randomly assigned, half to the dietary replacement group and half to the written materials  group. The study lasted for 16 days.

Days 1-5 were Baseline Days during which the study was explained, instructions and materials such as glass food storage contains were provided, and detailed dietary questionnaires were completed for each family member every day. The written materials group was given written guidelines to reduce phthalate and BPA exposure, including descriptions of phthalates and BPA, sources of exposure with a focus on plastics, and suggestions for how to reduce exposure in daily activities. Urine samples were collected from all family members on Day 5.

Days 6-10 were Intervention Days. The dietary replacement group was provided with catered food from a local caterer who used fresh, local and, whenever possible, organic ingredients. The food was prepared, stored and transported without using plastics. Both groups were instructed to use filtered water, consume beverages from non-plastic containers when possible, use non-plastic utensils and dishware, and store foods in the glass storage containers provided. Dietary surveys were completed every day. A urine sample was collected for each family member on Days 9 and 10.

Days 11-16 were Post-Intervention Days. Dietary surveys were completed every day and urine was collected on Day 16.

Here's what they found:  There was a significant increase in phthalate metabolites during the intervention period compared to the baseline period for the group that ate a catered diet. The average phthalate level in the dietary replacement group when they ate the catered diet (Days 9 and 10) was 25 times the level at baseline (Day 5). This was a complete surprise! In contract, they found no change in urinary phthalate metabolites in the written materials intervention group between baseline and intervention.

Since the increase in urinary phthalate concentration in the dietary replacement group was unexpected, the researchers tested the food ingredients in the dietary replacement group to see if there was phthalate contamination. They found that the dairy products milk and cream had phthalate concentrates above 440 ng/g, and that the spice mix had very high concentrations, 700 ng/g in ground cinnamon and cayenne pepper and the astounding level of 21,400 ng/g in ground coriander. All other ingredients had phthalate concentrations in the range reported in the literature.

The researchers had hoped to see reductions in urinary phthalate metabolites in both groups, but expected that providing written materials would be less effective than providing catered organic food prepared without exposure to plastics. But that was not what they found. Instead, they concluded that accepted methods to reduce dietary exposure to phthalates and BPA (e.g. minimize contact with plastics) may not actually reduce urinary concentrations of these chemicals. This study highlights how contaminated foods can contribute to excessive phthalate exposure. However, it is not known whether this was a isolated and rare contamination event or whether the food supply is systematically contaminated with high phthalate concentrations.

With no change in phthalate and BPA levels between baseline and intervention days in the group who received written materials, the trial supported the team's hypothesis that providing written recommendations to reduce dietary exposure to plastics is insufficient. This is corroborated in primary practice where it has been shown that written guidelines are ineffective to change health-related behaviors.

Families can focus on buying fresh, low-fat foods and avoiding plastic packaging and dishware. But this study demonstrates that it may take federal regulation to eliminate phthalates from the food supply.

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