Mercury Toxicity - Is Your Whey Protein Worse than Your Amalgam Fillings? Maybe, but That's not so Bad, Anyway...

Could your whey protein contribute more to your mercury exposure than your 20-year old amalgam fillings?

30 years ago Eggleston, et al. published a paper in "The Journal of Prosthetic Dentistry" which confirmed that there is a statistically significant "positive correlation between the number of occlusal surfaces of dental amalgam and mercury levels in the brain (p < .0025 in white matter)" (Eggleston. 1987). Only recently Bentsson et al highlighted that modern amalgam fillings may leak even more of the toxic substance into your saliva (from where it will take a tour around your body). And earlier this year the European Union banned amalgam fillings - albeit only for kids and without admitting that they are a definite health threat.
You already knew all that? Well, in that case, you were probably also aware of the fact that the dietary and environmental mercury exposure of the average Westerner will significantly outweigh the contribution of amalgam fillings to your daily mercury load. Furthermore, I would venture the guess that you are soon going to tell me that you're avoiding high-mercury fish, live in a very clean area and don't buy food and other products from China, right? That's all good for you, but have you ever thought about the mercury content of your beloved whey protein?

Table 1: Sources and estimates of daily human exposures to various forms of mercury (Gochfeld 2003).

No!? Well, I have to admit, I haven't done that either... at least not before I hit on Leticia Fraga Matos Campos de Aquino's latest paper in the Journal of Food Composition and Analysis (de Aquino 2017).
It's a study in which the authors measured the total mercury (THg) content of nineteen brands of whey protein with different formulations and estimated the potential health risks of mercury exposure to humans through whey protein consumption.

Figure 1: Total (organic + inorganic) mercury content of 19 samples of whey proteins from Brazil (de Aquino 2017)

As you can see in Figure 1 the exact amount of mercury in the nineteen (undisclosed) whey protein products varies significantly, ranging from 0.548 ± 0.029 ng/g 9.41 ± 0.295 ng/g of whey protein. Sounds pretty bad, right? Well, as the authors point out, "[t]hese concentrations [are] below the maximum limit for food products" (de Aquino 2017). Still, the scientists' calculations indicate

"that potential health risks related to exposure to total mercury from whey protein ingestion need more attention from researchers and more studies are needed, especially including specific intake of mercury from other food products that are included in a balanced diet" (de Aquino 2017).

Eventually, only more sophisticated follow-up studies will be able to assess the influence of the other components in whey protein, its solubility, the metal oxidation state, the retention percentage, the intake frequency, and the absorption rate and efficiency of excretion mechanisms and thus to determine if the up to ~300 ng of mercury you could be washing down with every 30g shake is a significant threat to your health, or not. As of now, it appears to be very unlikely, though - if nothing else than because a US study shows that a single serving of fish (228g) bought in New Jersey could contain 50000 ng or 50µg according to a 2005 study by Burger, et al (learn more about mercury in fish).
References:

• de Aquino, Leticia Fraga Matos Campos, et al. "Mercury content in whey protein and potential risk for human health." Journal of Food Composition and Analysis (2017).
• Bengtsson, Ulf G., and Lars D. Hylander. "Increased mercury emissions from modern dental amalgams." BioMetals (2017): 1-7.
• Burger, Joanna, and Michael Gochfeld. "Heavy metals in commercial fish in New Jersey." Environmental Research 99.3 (2005): 403-412.
• Egan, S. K., et al. "US Food and Drug Administration's Total Diet Study: intake of nutritional and toxic elements, 1991–96." Food Additives & Contaminants 19.2 (2002): 103-125.
• Eggleston, David W., and Magnus Nylander. "Correlation of dental amalgam with mercury in brain tissue." The Journal of prosthetic dentistry 58.6 (1987): 704-707.
• Folwaczny, Matthias, and Reinhard Hickel. "Should amalgam fillings be removed?." The Lancet 360.9350 (2002): 2081.
• Gochfeld, Michael. "Cases of mercury exposure, bioavailability, and absorption." Ecotoxicology and Environmental Safety 56.1 (2003): 174-179.
• Larkin, Marilynn. "Don't remove amalgam fillings, urges American Dental Association." The Lancet 360.9330 (2002): 393.
• Rice, Deborah C. "The US EPA reference dose for methylmercury: sources of uncertainty." Environmental research 95.3 (2004): 406-413.
• Rose, Martin, et al. "Dietary exposure to metals and other elements in the 2006 UK Total Diet Study and some trends over the last 30 years." Food Additives and Contaminants 27.10 (2010): 1380-1404.