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This week's topic: Mercury and Human Health
Are you well-versed in the health effects of mercury?
- There are 3 primary forms of mercury; which form can cross the BBB and affect the brain?
- What molecule in fish complexes with methylmercury (MeHg) and may prevent mercury from being absorbed?
- Which is the best method for evaluating MeHg body burden: blood, urine, or hair?
- Which form of mercury does DMSA or DMPS mobilize best?
You can find the answers to the above questions below!
To prepare for this newsletter, I read the Clinical Environmental Medicine textbook chapter on this topic, perused PubMed articles (focusing on human studies), and brought in my clinical experiences.
Overview of today's email:
- Overview of Mercury (with a Practical Clinical Pearl on testing)
- Clinical tip on Mercury in Fish
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1. Overview of Mercury
There are 3 forms of mercury:
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Elemental/Metallic
- Most exposure is from vapor (especially amalgams, which are 55% mercury; 9x higher exposure to mercury vapor in those with amalgams); if metallic mercury comes from the environment, it is often methylated by bacteria or algae (and this MeHg is what fish absorb)
- Fat-soluble
- Can cross BBB
- Half life is 1 day to 3 weeks, mainly eliminated via urine
-
Methylmercury (MeHg)
- Mostly found in fish
- Fat-soluble; can cross BBB if bound to L-cysteine (but L-methionine blocks absorption), so this form is potentially the most detrimental to human health
- Half life is 70 days in blood (longer half life since 70% of mercury is reabsorbed in the gut)
- Hair testing in particular can assess for ongoing MeHg exposure, but blood mercury is also mostly MeHg
-
Inorganic mercury
- Water soluble
- If exposed, mainly the kidneys are vulnerable
- Biphasic elimination process - rapid phase followed by slower phase (half life can be 1-2 months, per animal studies)
- Urine mercury levels tend to have more inorganic than organic mercury, and DMPS or DMSA provocation primarily mobilizes inorganic mercury (but there must be adequate L-cysteine or GSH available, since heavy metals that are "grabbed" by DMSA must be conjugated with L-cysteine)
Symptoms
Neurological symptoms are the primary result of mercury toxicity, but hypothyroidism, hypertension, persistently elevated ALT, hair loss, and musculoskeletal pain can also be connected to chronic mercury body burden.
In those with amalgams who have these removed and undergo a chelation protocol, the primary symptoms that improve are:
- Fatigue
- Depression
- Memory
Testing
Blood and hair testing mostly evaluates for recent or ongoing MeHg, and urine testing reflects some MeHg exposure but more inorganic mercury. Although I found mention of a saliva or vapor release test for mercury, I could not find any great scientific article that validates a "best" method for evaluating elemental mercury burden from amalgams.
Use NHANES criteria for evaluating whether a blood or urine mercury level is elevated (mostly due to recent exposure). The following values are for those that are in the 75th percentile or higher for mercury levels:
- Blood: Over 1.38 mcg/L
- Urine: Over 0.67 mcg/G-CRE
Testing (with references) was discussed in more detail in a previous newsletter, and a table of NHANES values is included in the extended (paid) Substack newsletter on heavy metal testing! But if you want to take a deep dive into mercury specifically, peruse this article.
Practical Clinical Pearl on testing:
If you see persistently elevated levels of mercury in blood, and the patient has avoided fish for at least 5 days before testing, test hair and urine levels. If hair and urine levels are low, this may be a result of genetic polymorphisms affecting glutathione enzymes, selenoproteins, or metallothionein. These individuals may be less able to excrete mercury and are more susceptible to the damaging effects of mercury.
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2. Clinical Tips on Mercury in Fish
It has been an ongoing discussion and source of research to determine the negative health effects of mercury in fish.
However, fish and seafood are high in selenium. And there are many benefits to consuming fish!
Selenium irreversibly binds to mercury, forming a SeHg complex.
So when we consume these foods, even if we see elevated mercury levels in blood or urine after recent consumption, the SeHg complexes may not be diffusing into tissues and causing harm.
Note, there's more research coming out on the ways mercury induces genetics and is affected by epigenetics. I may see if Dr. Sharon Hausman-Cohen (founder of IntellexxDNA) can do a talk on this. If anyone is interested in this talk, reply to this email! If there is enough interest, we can get this on the schedule for 2026!
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If you want to take a deep "practical" dive with me and the FMC members on the topic of MCAS, I am doing a 6 week workshop on this topic from February 1st through mid-March! More information to come in the next newsletter!
And as a reminder, if you are looking for support and mentorship, join the Functional Medicine Collective (FMC)! In this (intentionally) small collaborative community, I aim to get to know each member and their unique challenges as we navigate the nuances of real-world functional medicine. There is a $49 a month option (no access to mentor calls), and $99 a month option (includes mentor calls). Click on one of the buttons below to learn more!
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I hope this was clinically useful!
To see my deep dive into the literature on therapeutic treatments to reduce mercury levels and minimize mercury-induced damage, and hear more of my thoughts and experiences on testing and treatment of mercury toxicity, subscribe to my paid Substack ($8 a month) for the extended version of this email!
Meg
P.S. These emails take a lot of time to create (and I don't receive a lot of feedback on whether they are useful to those that receive them), so I've moved to Substack for an extended version of these at a low monthly cost (available within 24 hours of releasing this email). Why Substack? It has the benefits of being able to comment and ask questions about the posts, you're not bombarded with ads, I'm using the platform as a "micro-mentorship", and it's low cost!
Additional resources that may be helpful:
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