The slimemoldtimemold.com series “A Chemical Hunger” has been a mother lode for things worth talking about in understanding the rise of obesity. I have written three posts in reaction already:

1. Are Processed Food and Environmental Contaminants the Main Cause of the Rise of Obesity?

2. Livestock Antibiotics, Lithium and PFAS as Leading Suspects for Environmental Causes of Obesity

3. How Rising Anorexia Can Go Along with Rising Obesity: Both Can Be Caused By Environmental Contaminants

Overall, I find the argument persuasive that there is some role for environmental contaminants (such as livestock antibiotics, lithium and PFAS) in the rapid rise of obesity since 1980. Sometimes the author goes too far by suggesting that another thing is not contributing because it doesn’t explain part of the observed pattern. But there is every likelihood that environmental contaminants and other causes are contributing to the rise in obesity in general. It may be that the facts can’t be explained without environmental contaminants as part of the picture, but it is easy for other factors to contribute to an overall upward trend both before and after 1980.

A good example of this is that obesity rose across the board for Native Americans as their diets and other aspects of their lives modernized, but obesity rose especially sharply for the Pima, beginning in 1937. The slimemoldtimemold blog focuses on this issue in response to the following comment to that blog:

In another comment, u/evocomp raises a number of points, the most interesting being:

The famous Pima Indians of Arizona had a tenfold increase in diabetes from 1937 to the 1950s, and then became the most obese population of the world at that time, long before 1980s. Mexican Pimas followed the trend when they modernized too.

Slimemoldtimemold fully agrees that there is a mystery to be explained:

The Pima people, sometimes called Pima Indians, are a group of Native Americans from the area that is now southern Arizona and northwestern Mexico. In the United States, they are particularly associated with the Gila River Valley.

What evocamp describes is well-documented. The Pima seem to have had normal rates of diabetes and obesity in 1937, but both increased enormously by 1950, and by 1965 the Arizona Pima Indians had “the highest prevalence of diabetes ever recorded.” By 1970 the diabetes rate was around 40%, and by 2016, around 50%. The numbers on obesity are less specific, but it was also increasing and also very high by the 1970s.

The timeline here is very surprising — before 1970, obesity rates worldwide were almost always 10% or less. This is clearly a mystery that needs to be accounted for, so we really appreciate evocamp pointing us to this example.

Moreover, this was a pattern not seen at that level for other Native American groups:

There were many other groups of Native Americans living in largely similar conditions all over the country, but none of these groups were around 40% obese by 1970. It can’t be food or shelter or oppression by the US government because these things were more or less common to all groups …

Why then? Here is the proposed explanation:

… the difference between the Pima and other Native Americans is that the Pima were being exposed to huge doses of lithium in their food and water and other groups weren’t.

The Pima did seem to be exposed to a substantial dose of lithium in their groundwater:

The report also notes that “lithium is found in the groundwater of the Gila Valley near Safford.” There’s also this USGS report which says a Wolfberry plant (genus Lycium) “was sampled on lands inhabited by the Pima Indians in Arizona; it contained 1,120 ppm lithium in the dry weight of the plant.” To give that number some context, “an average of 150 ppm lithium in the ash and 25.8 ppm in the dry weight of all plants that were collected in both closed and open arid basins is considerably higher than the average of 1.3 ppm in dry weight reported for plants growing in a nonarid climate.” There was serious lithium contamination in this valley as early as 1974!

Also regarding the 1974 source, another USGS report says, “Sievers and Cannon (1974) expressed concern for the health problem of Pima Indians living on the Gila River Indian Reservation in central Arizona because of the anomalously high lithium content in water and in certain of their homegrown foods.”

We couldn’t have cherry-picked this example, because u/evocomp proposed it.

Overall, this is a very interesting piece of evidence that we should be worrying about lithium in our water supply—both in drinking water and in water used on farms.

For organized links to other posts on diet and health, see:

• Miles Kimball on Diet and Health: A Reader's Guide