According to U.S. government data, dairy products are the primary source of calcium in the American diet.
That’s a primary reason to include dairy in our dietary intervention study of the human effects of Bisphenol A and other plastic-derived environmental chemicals. Indeed, some studies consider milk as an almost nutritionally complete food.
And while dairy consumption is a relatively recent phenomenon — evident in pottery shards, ancient bones, and plaque from Neolithic teeth, indications are that it provided a significant evolutionary advantage among ancient humans who consumed it.
In fact, one significant 2004 study indicated that humans with the mutation which allowed the human digestion of lactase would have produced up to 19% more fertile offspring than those who lacked it. The investigators of that study termed that increase in natural selection advantage “among the strongest yet seen for any gene in the genome”
Multiple confounding factors complicated the study protocol
Our study was originally approved in November 2014 by the Committee on Human Research at the University of California San Francisco Medical School. But, as we worked to make sure that our study could be replicated by other investigators, we ran into massive issues with sourcing uncontaminated foods.
For dairy products, we created a ultra-strict sourcing protocol that assumed that the introduction of plastic chemicals into the dairy food chain begins with the milking process.
That assumption was based on the dairy chain’s many contamination sources from plastic-derived chemicals (BPA and phthalates. Plastic-based materials, coatings, tubing, pipes, liners, valves and other components in the milking machines and in materials used in the transfer of milk to holding tanks, cooling tanks, and truck transport the creamery.
In addition, once at the creamery, there are polymer-based components used for the movement of milk through filtering, pasteurization, cream separation, homogenization, and finished packaging.
Back to the future for the sake of replicability
Based on this set of assumptions, we hypothesized that the minimum contamination and the best chances of replicability of the study demanded a “back to the future” effort that required us to acquire raw milk — milked by hand (with conditions).
That protocol then required us to:
- pasteurize the milk
- use a cream separator to produce different butter-fat components that were appropriate for:
- consuming as milk,
- making cheese, and
- churning butter.
How “Back to the future failed”
After our study received a one-year extension by the UCSF Committee on Human Research in late 2018, we set out to obtain the milk that we needed for that.
Unexpectedly, we ran into a stonewall of silence and lack of cooperation from the dairy industry. That resulted in months of failure to get even a reply from dairies, creameries, farm organizations, ag-oriented educational institutions — even — cheese and yogurt makers — anyone who might know a dairy farm who would cooperate.
That frustrating effort is told in more detail in this DRAFT post “No milk for research!” (A Sisyphian tale … still in progress).
Aggravating the milk acquisition problem was the fact that we bought a cream separator — said by the seller to contain no plastic — full of plastic parts and “stainless steel” that was actually aluminum. That will be the subject of another article and associated photo essay.
So, there we were in July 2019 with two new major problems.
New confounding problem solves the two previous problems. (Sort of)
While we were knock, knock, knocking on dairy’s door, the lack of cooperation from dairies and creameries combined with the inability to obtain an appropriate cream separator sent us back to our towering pile of scientific literature in search of a valid path from this latest dead end.
That paper upended our concept that the least-contaminated milk would be obtained by hand, rather than via machine milking which has many plastic components.
That paper noted that, “The mean BPA concentrations were 0.757 µg/L in manually milked samples, 0.580 µg/L in mechanically milked samples, and 0.797 µg/L in milk from the cooling tank.”
Unexpectedly, hand-milked had a higher concentration of BPA than milk samples obtained by machines!
That sent us back to an extensive literature search which revealed that there is little data done on looking at BPA/phthalate contamination along the entire dairy production chain. However we found a remarkably thorough 2012 paper that looked at the entire chain beginning with groundwater.
That paper found that phthalate concentrations were inconsistent: machine-milked samples were sometimes more contaminated than those obtained by hand … and vice-versa.
While not mentioned by either of these two papers, it’s notable that people who hand-milk cows wear polymer-based gloves which could be a source of contamination.
Regardless, these study results of inconsistencies disproved our hypothesis that the least-contaminated milk would come from hand milking.
Even more significantly, the study found further inconsistencies in contamination depending upon the seasons, silage (feed) as well as in the cooling tanks, and the trucks used to transport the raw milk to the creamery.
Those inconsistencies are further complicated by variations in the presence of plastic materials associated with different creamery operations: pasteurization, cream separation, homogenization and consumer packaging.
This meant that there was no valid way of predicting BPA/phthalate levels based upon intercepting samples at the milking stage.
Finally, because the dietary significance of dairy demands that it be included in our intervention diet, the only remaining tactic was to have commercial samples directly tested to select the “before” source and the “after.”
And while we would have milk to drink and to make cheese, the lack of a valid cream separator meant that making butter would be impractical given the 4% butterfat of commercial milk.
The new milk measurement
I dug deep into the vacation fund and bought six samples to be tested at Eurofins, a large international commercial laboratory corporation which has a facility in Fresno specializing in food analysis. It’s accredited to the ISO 17025.
The milk with the highest level will be used in the “before” diet and the lowest in the intervention.
All are whole milk ( approximately 4%) except for the 2% reduced fat at the far right.
From left to right: Safeway supermarket brand, Clover (large local creamery), Whole Foods Brand, Organic Valley, Straus Family Creamery (local organic creamery) and Straus Family Creamery 2%
All were sourced at Whole Foods Market and Safeway in the town of Sonoma on September 3, 2019. The items were placed in a cooled ice chest immediately after leaving the store.
All were stored in a refrigerator at 35 degrees F within half an hour of the first purchase.
I attempted to avoid plastic packaging which has higher levels of BPA and phthalates, but the Whole Foods milk was only available in plastic. Straus was only available in glass.
In order for this analysis to be reproducible by other investigators, I chose products that are more easily obtainable nationwide. Those opportunities are enhanced by obtaining them at a national (Whole Foods) or a very large regional chain.
I also chose the Straus products because they were the first organic creamery in the United States uses “minimally processed” processes and packaged in glass to avoid plastic food contact chemical contamination. I hypothesized that they are likely to show the lowest BPA levels.
All samples remained unopened until the day that samples were transferred to freshly cleanedm 120 ml glass bottles which had been triple rinsed with carbon-filtered water. Aluminum foil was placed over the mouth of each bottle to prevent contact with the plastic cap.
A few photos are below. I have photos of the expiration dates and nutrition labels as wel.
Relevant supplemental links
Phthalate Concentrations and Dietary Exposure from Food Purchased in New York State Published:1 April 2013https://doi.org/10.1289/ehp.1206367 (open access)
Zota A, Calafat A and Woodruff T (2014) Temporal Trends in Phthalate Exposures: Findings from the National Health and Nutrition Examination Survey, 2001–2010, Environmental Health Perspectives, 122:3, (235-241), Online publication date: 1-Mar-2014.
Phthalates in Belgian cow’s milk and the role of feed and other contamination pathways at farm level https://doi.org/10.1016/j.fct.2012.05.036
Determination of free and total phthalates in commercial whole milk products in different packaging materials by gas chromatography-mass spectrometry https://doi.org/10.3168/jds.2015-10066