Food selections for both legs of the study were patterned after a “typical American diet”as defined by the United States Department of Agriculture (USDA).
In addition, identical (or extremely similar) foods chosen for each leg needed to be widely available in the United States in a practical manner convenient to other investigators.
Absent an unrealistically massive budget that would allow LC/MS testing on every food component in both legs of this study, certain assumptions needed to be made regarding food sourcing and the effects on replicability.
Investigators based those assumptions on (among many considerations) on how food processing adds plastic-derived chemical (PDC) contamination and the ways that PDCs infiltrate the food chain.
Baseline leg
For the “typical” plastic-contaminated baseline leg, food was sourced from national brands available at a large chain store, Safeway. While there are no truly national food chains[x], large regional chains such as Kroger, Safeway and others offer many of the same national brands.
Because national brands are processed according to consistent corporate manufacturing standards [x] investigators gave them preference. This is preference based on an unverifiable assumption that, for example, Oreo cookies purchased at a California Safeway are likely to have the identical (or close to) nutritional composition and plastic-derived chemical contamination as Oreo cookies purchased in Ohio, New York or Florida.
In addition, processed foods provide nutrition information that is likely to be relatively accurate and probably consistent regardless of the purchase location. Further, these foods experience a higher degree of processing than fresh foods which exposes them to numerous additives and polymer surfaces[x]. lastly, these national brands are frozen, canned, and packaged in other extended-shelf life materials which are substantially plastic-based[x].
That set of assumptions also postulates that these foods are likely to provide sufficient plastic-based contamination levels to contrast with levels in the intervention leg.
It’s important to acknowledge that many items in chain stores — such as fresh fruit, vegetables and milk — are obtained from local or regional sources whose contamination levels likely vary widely. Investigators in this study, therefore, relied upon frozen fruit and vegetables for the contamination leg.
Because milk is sourced locally or regionally even by large chains we had milk samples analyzed via LC-MS/MS which offers future investigators the advantage of choosing milk with the same or similar BPA quantification. This testing was also performed because our original protocol called for using the least contaminated milk to produce our own cheese. Time constraints and other issues of practicality make that unfeasible. We elected to select cheese from a nationally available dairy brand whose milk scored below LOQ in the LC-MS/MS tests.
Food Sourcing: Intervention leg
For the intervention leg, food was sourced as close as possible in the food chain to its actual production from a vendor capable of shipping nationally.
Investigators developed detailed standards for intervention food selections based on literature searches detailing detected or projected contamination sources. Special attention was devoted to the health effects of micro- and nanoplastics and to minimizing exposure to those particles.
Key for these considerations were that the producer:
- Either dry-farmed or used well water for irrigation
- No irrigation with recycled wastewater or biosolids (sewage plant sludge)
- Adhered — as a minimum — to USDA organic standards
Food was sourced by the ability to trace items to the source of production, and vetting of the source for complying with standards according to food type.
The exhaustively detailed standards used are described in Appendix 2 of the Revised Stealth Syndromes Human Study Protocol,
If the absence of contamination could not be determined, then specific foods were considered contaminated and eliminated from the intervention diet. Some entire classes of food — such as fish and seafood –were excluded because the constant environmental pollution variability makes it impossible to assess contamination potential (fish).