Can heavy metals like mercury, lead, or cadmium play a role in developmental disability? We have known for decades that the answer is an emphatic yes. Toxic heavy metals can cause developmental injury and many other problems. Babies and young kids are especially vulnerable, both because of the timing of exposure when the brain is developing, and because of dose. Babies and kids are a lot smaller than a teen or adult!
The only routine screening children get for this is a blood test for lead. There is no safe level of lead according to the CDC, but an arbitrary cap of 10 micrograms per deciliter (ug/dL) of blood has been set as a cut off. The dilemma with this well intended measure is that lead – and other heavy metals like mercury, arsenic, or cadmium – don’t like blood. They don’t like watery environments. They are lipophilic – meaning they naturally migrate to fatty tissues. Brain, nerve cell coating (myelin), cell membranes (which contain fatty molecules), and kidney are favorite fatty targets. Lead, mercury, cadmium, arsenic – when measured in blood, only a recent or active exposure will be captured, because these metals move out of blood and into fatty tissues relatively quickly. Lead will move out of blood in 2-4 weeks; mercury can migrate out of blood and into brain in as quickly as 3-5 days, and both ethyl and methyl mercury forms are noted to cross into brain tissue. Once deposited in fatty places, these can wreak oxidative and inflammatory havoc. While still in blood, they effectively bump essential minerals like iron, zinc or copper off the functional pathways we depend on for cellular function.
One of the clues that this may be an issue at any age is a behavior called pica. Pica means eating non-food objects, especially metal. Here’s the extreme example that prompted me to write this blog! –>
A friend of mine is a care provider for a disabled adult. She told me a little about this client, who in his forties, and what kind of care he needs. He is infantile due to a head injury as a boy. She happened to mention, “he has pica” – so, all sorts of non-food things have to be kept out of his reach lest he eat them or chew them. Well, he can’t chew, she explained. He doesn’t have teeth, so all his food is pureed. No teeth at all.
Why no teeth, I asked. Did they all rot? Did he lack access to dental care at some point? Does he have poor immune function? My friend wasn’t sure because the teeth were gone when she began working with this man, but she implied his teeth were removed because of his pica “behavior”.
Somewhere along the way, apparently, it was decided that the best solution to this behavior was to remove all this man’s teeth.
I hope this isn’t true. I’m hoping there is a reasonable explanation for why this individual no longer has teeth – besides ignorance on the part of a physician or dental surgeon somewhere – but my friend confirms that this disabled man’s primary care doctor has told them that pica is purely a behavior.
Not exactly. Pica is a well-known clinical sign of iron deficiency anemia. It also indicates other mineral imbalances or deficiencies – like zinc or magnesium deficiency, or copper or lead toxicity. Mouthing or chewing objects is expected for teething babies, or during the developmental phase when oral exploration is key. Beyond that, persistently eating things that aren’t food – erasers, dirt, sand, rocks, clay, metal objects, plastic, wood, ice – should be regarded as a flag for iron deficiency anemia, zinc deficiency, or mineral imbalances for magnesium, copper, lead, cadmium, or manganese.
Could it be in this day and age that such a fundamental tenet of nutrition was overlooked? Or even more crazy, that it might have cost a developmentally disabled adult who can’t speak for himself every tooth in his head? Was this man’s suffering avoidable?
Possibly. His head injury may have left him with pica that is purely behavioral or developmental in origin. But, it’s simple to screen for mineral imbalances by checking clinical signs and lab tests. My friend tells me she has no idea if anyone ever did this for this man. It can be straightforward to correct pica with the right nutrition measures. When this is done, pica “behavior” can resolve or improve – as can other behaviors that attend mineral deficits or toxicities, like aggression, attention deficits, criminality, or even schizophrenia.
Pica can mean that minerals necessary for learning, growth, behavior modulation, and development are not fully on board, or that they have been displaced by toxic minerals instead. It’s common in people with developmental disabilities, including autism – no coincidence, given the known neurotoxic effects of excessive lead, cadmium, copper, or mercury. Deficiency for essential minerals for a growing fetus, and in the zero to three years, is well documented too. An iron deficiency for mom during pregnancy – all by itself – can cause a full term baby to be born at low birth weight (less than 5 lbs 5 oz or 2500 grams). Stunting, learning delays, behavior problems, attention deficits, and lower IQ have all been linked to pica and/or mineral imbalances in babies and toddlers. Pica can also predispose people to greater lead exposure, for two reasons: They may ingest objects containing lead; and, the lower one’s iron status is, the easier it is to absorb more lead, with any exposure.
Before it’s assumed that eating weird stuff is just a behavior – especially in a developmentally or learning disabled person – a doctor should do a full iron study. Blood work should assess ferritin, serum iron, total iron binding capacity (TIBC), hemoglobin, and hematocrit. Your doctor might look at red blood cell shape, size, and number to fully rule out anemia or pre-anemia. Reference ranges for iron parameters are wide. Children should fall solidly in the middle of the ranges for ferritin and serum iron. Teetering at either edge of the range, high or low should prompt more investigation. Marginal iron markers often go hand in hand with inattention, insomnia, picky appetites, or behavior and learning deficits. It is also wise to check serum copper, serum zinc, and ceruloplasmin (a copper transport protein in the blood), to rule out toxic levels of copper. Copper circulating unbound in serum can become neurotoxic, while ceruloplasmin will safely transport this mineral for us. Adequate zinc status can keep copper levels in check.
People with iron deficiency anemia often have pica for pebbles, ice, sand, dirt, clay or metal objects. Those with poor zinc status often uncontrollably chew fabric, clothing, erasers, wood, or pencils, or clench and grind teeth, in sleep or when awake.
One caveat: If iron supplementation is warranted per your provider’s advice, make sure your child is not ill, with a fever, or has active infections, including gut candida infections. Microbes love iron, and will thrive when it is supplemented – which can make your child feel some GI discomfort at the least, or worsen a fever, trigger pain, and worsen behavior outbursts. Iron is also poisonous at the wrong dose, so only use supplements with professional guidance.
To learn more on how kids present when they need iron, zinc, or other minerals, or when they may have toxic mineral loads, see Special Needs Kids Eat Right. Correcting mineral balance is an easy nutrition fix that is worth the effort. Check status of all essential minerals and rule toxic mineral exposures, to really know if pica has a physiological underpinning. Toxic minerals don’t remain in whole blood for long, so a knowledgeable practitioner may want to check packed red blood cell elements to more accurately assess presence of toxic metals. Optimizing minerals means optimizing many pathways in the brain for learning, processing, and emotional regulation – something that will benefit any person with a developmental disability – without pulling all their teeth!
My 3 yo girl has Down syndrome and eats loads of non food items. She particularly favours rubber and plastic. Even knows where to find it without knowing if you know what I mean..opens the fridge drawer and bites the seals. And the seal around the boot of the car if the door is opened.. what could this possibly indicate?
This warrants a conversation with your primary care doctor. Teething at this age would be unusual even for a child with Down’s syndrome – teeth often come in later than in kids without Down’s syndrome, but typically by now baby teeth are in. If this is a new behavior with an abrupt onset, some screening is worthwhile for mineral status. Ask for bloodwork on nutrient elements like iron, copper and zinc. Screen also for toxic metals like lead, cadmium and mercury. The caveat is heavy toxic metals don’t linger in the blood stream – they hate watery environments. They quickly shift into fatty tissues where they can park indefinitely, displace the necessary nutrient minerals, and become damaging. If you haven’t already, have a dental check up too to make sure there are no issues for pain, infection, or misaligned teeth that might cause her to want to clamp on soft rubbery materials.
My son is eating non food items. Soap, sanitizer, plastic, dirt, things/water from dirt utensils. His iron and zinc levels are good. What other things we could check ?
First, I assume your child is past teething and infancy/early toddlerhood when anything goes in the mouth for exploration.
Next, I wonder what exactly illustrated the iron and zinc levels as “good”. There are detailed iron studies, and then there are less sensitive crude tests, like simply looking at hemoglobin. Hemoglobin tests don’t measure iron itself, and can be in a normal lab range even with iron deficit or other types of anemia. Lab tests can measure serum zinc level, or red blood cell zinc level. If all were checked, all should fall solidly in the middle of the lab reference ranges – not toward the low end, which often describes a marginally deficient state that may trigger pica behavior.
If that truly all looks good, then screen for heavy metal toxicity from mercury, cadmium, lead, or aluminum to start. These are generally not reflected accurately with blood samples alone, because these metals do not like watery environments like blood. They target fatty tissue (brain and kidney especially), where they can get stuck if the body has poor detoxification chemistry.
To test for these heavy metals using a blood sample, the best option is to measure the amounts of heavy metals found inside red blood cells, which have some fats in their cell walls that can retain heavy metals. This is an example of that test. Your pediatrician is not likely to be familiar with this, but you can contact the lab and ask about access to providers who are.
I don’t use hair as a sample for heavy metal testing as I don’t believe it to be very useful or accurate. For example, children who have poor detox won’t push mercury out in hair, as was demonstrated in this study on hair of children with autism.
To use stool or urine tests for heavy metals, a chelating agent – that is, something to pull the heavy metals out of fatty tissue – is needed. You can learn more about removing heavy metals here.
My 2 year old daughter always wants to chew on anything metal. Should I be concerned?
Yes, ask for an iron and lead screening with your pediatrician.
Hi thank you for this information, I found this very interesting. My daughter constantly wants to chew paper. What type of deficiency would you suspect?
I would suspect zinc deficit in kids who like to chew paper, fabric, their own hair. Download my Sensory Nutrition Checklist for more details on this.
What deficiency is present when one chews plastic? Iron or something else?
This is suspect for iron as well as zinc deficit, and for toxicity with heavy metals like lead. In my practice I pursue those screenings for kids who are doggedly determined to chew and swallow plastic, dirt, ice, rocks, sand, sticks, fabric, metal objects, paper and cardboard.
When my daughter Cameo was around 2 and a half she got very sick. She started to eat coloring crayons. She had never tried to eat non food things before this even as a baby. I had to hide all the crayons because if she saw one she would quickly put it in her mouth and start eating it. She was even hunting around looking for them. She was lethargic and had very loose stools. I took her to ER because I knew there was something wrong.
When we saw the doctor he told me that it is normal for a two year old to eat crayons and to not worry about it. I said she is not acting the way she normally does and that something is wrong with her. She was limp in my arms. I asked if it could have anything to do with the lead poisoning she recently had. He said she no. She did get better in a few days and stopped craving crayons but I wish he would have done some tests.
How horrific to pull out all his teeth because of a behavior. I hope that’s not really the case, but if it is, it’s criminal.
My mother in law has struggled with bipolar her whole life, and became bulimic late in life (around age 40). As she hit 50, her teeth started rotting and falling out, and she had to have them all pulled eventually. She described the pain to me, and said she wouldn’t wish it on anyone.
I don’t think they pulled them. He probably damaged them eating non-food items, cracking them or wearing them down.
Good point Sara! Even in that case, the question of why anyone is eating non-food objects to such an extent that they have damaged their teeth can be investigated and corrected with less invasive measures.