In a previous post, we examined whether lead exposure was responsible for worsening ADHD symptoms. We saw that there is a solid (although still somewhat hypothetical) connection between lead and hyperactive behavior. This lead to the blog's conclusion that high lead levels (the exact amount is still hotly debated, but a federal recommendations appear to be headed to a cutoff of around 10 micrograms lead/deciliter of blood. This converts roughly to half of a gramof leadtotal in the entire blood supply in the average adult male, or less than half a gram of lead total in a child's blood ). This post can be found here.
A follow-up post suggested that adequate iron intake can help counteract some of lead's negative effects on ADHD and related symptoms through a variety of possible mechanisms. A link to this blog post can be found here.
Now it appears that another metal may be connected to hyperactivity. While the connection between manganese and hyperactivity appears to be more strained that that between lead and hyperactivity, it is at least worth mentioning. Additionally, manganese seems to be less tied to actual ADHD behavior (including inattention and impulse control problems alongside hyperactivity), and more towards generalized hyperactivity. Nevertheless, like the post on lead and hyperactivity mentioned previously, there at least remains that possibility that unhealthy buildup of manganese in the body may lead to hyperactive behavior. This could, at least hypothetically, "push" an individual with the predominantly inattentive form of ADHD to more of a mixed or combined subtype of ADHD, which includes hyperactive/impulsive behavior as well. A study of French Canadian children who lived in an area with naturally high levels of manganese found a significant tie-in between high manganese levels and hyperactive behavior. A summary of that study can be found here. Some key points of the article (along with some of my thoughts and comments) are listed below:
While the study made several noteworthy observations, there are too many loose ends and questions left to be answered before determining whether manganese can pose similar risks to lead as far as inducing hyperactive behavior and ADHD-related symptoms. As of now, we are unsure whether the effects were do more to interference with iron absorption (given that numerous studies have shown that individuals with ADHD are typically iron deficient) or through a non-iron-based regulation of the GABA and dopamine pathways mentioned above. Further clouding this is the fact that iron itself plays a key role in dopamine synthesis and manufacturing.
As of now, my conclusion is that there is a possible correlation between high manganese and ADHD (especially the hyperactive form), but this connection is much weaker than that of lead (which is debatable in its own right at the moment). It certainly appears that manganese is more tolerable and overall more benign than lead, at least with regards to similar levels of exposure.
Unlike lead, manganese is actually a trace element micronutrient (i.e., it's good for the body at low levels). Manganese-rich foods include teas, beans, nuts and many types of whole grains. Additionally, excess manganese can be cleared more easily from the body than can lead. While common sources are food and drinking water (with water thought to be a more potent source of intake than food), inhalation is also a common mode of entry. This is especially true of specific occupations such as welders. Typical blood manganese levels hover around 1 microgram of manganese/deciliter of blood. This roughly translates into about .05 grams total manganese in the bloodstream.
It is easy and often tempting to try to assimilate anything and everything to a disorder such as ADHD. Many professionals and researchers often fall into this trap. However, I caution against this, since this clouds the picture as to what the real underlying causes of the disorder might be. That is why I urge restraint before passing judgment on this particular metal, at least in regards to its causative role with respect to ADHD and related disorders.
Certainly, manganese toxicity is a problem, with the deleterious effects of manganism (sometimes referred to as "manganese poisoning" and is characterized by loss of balance and coordination and impaired reaction timing) going back hundreds of years and still seen in certain metal-related occupations such as welding. Nevertheless, the relative ease of excretion of manganese (at least when compared to other heavy metals such as lead) and somewhat higher limits of tolerability make it a possible foe in the ADHD symptom world, but not a powerful one, at least for the time being.
In the next post, we will be shifting gears a bit and looking into the connection between celiac disease and ADHD and its degree of association with specific symptoms of the disorder.