Production of serotonin: This piggy-backs on the vitamin B6 role highlighted in point number 2 above. ADHD is often considered a disorder associated with the neurochemicals dopamine and norepinephrine. However, serotonin may also play a role in this disorder. For individuals who exhibit anxiety and depressive symptoms alongside their ADHD (which is surprisingly common), a serotonin deficiency is often partly to blame. Serotonin is synthesized in the body from the amino acid tryptophan. However, for this conversion process to go through, sufficient and functional vitamin B6 is required for serotonin to be formed by the tryptophan conversion process via a special type of enzyme known as aromatic amino acid decarboxylase. As previously mentioned, zinc is needed for functional vitamin B6, and therefore plays an indirect role in the synthesis of serotonin. Thus, zinc may be extremely important in individuals with ADHD and comorbid (co-occurring) depression or depressive-like symptoms.
Reduction of hyperactivty, impulsivity and antisocial behavioral symptoms: For direct treatment of ADHD, it appears that zinc may be more effective in treating the hyperactive/impulsive aspects of the disorder than the inattentive portion of the disorder. This study also noted the effectiveness of zinc for older children and children with a higher body mass index, which at least suggests that the effectiveness of zinc as a treatment for children with ADHD may increase as the child ages and grows.
Zinc may also play a role in the process of brain waves associated with ADHD as well as other disorders: We have already investigated differences and discrepancies in the brain wave patterns of ADHD children, including how these may actually be tied to an individual's genes. Information processing, which is often impaired in ADHD individuals, is believed to be tied to a brain pattern known as N2 (which is short for second negative wave, no need to concern ourselves with the exact details of this process here). Some research suggests that N2 mediated information processing may be negatively affected by zinc deficiency. This relates to unwanted attentional shifting (i.e. distraction) to irrelevant stimuli. In other words, N2 is related to the "novelty effect" of a specific stimulus or change in stimuli. As an interesting aside, N2 brain patterns are thought to be affected by serotonin, which, as mentioned in point #5, is indirectly tied to zinc levels. Based on this, it is at least plausible that zinc may play an integral role in this mechanism of distraction.
Boosting the effectiveness of ADHD medications: While we have reported on this in an earlier post on zinc and Ritalin, I believe it is worth repeating here. Multiple studies suggest that zinc can boost the effectiveness of methylphenidate for treating ADHD and related disorders. This may be of importance with regards to reducing some of the negative side effects associated with the drug. Many of these negative side effects often don't set in at the lower doses of the various forms of the drug, but instead, begin to appear with greater frequencies at higher doses. Taking this into account, it seems reasonable (at least in this blogger's opinion) that concurrent treatment with zinc may be enough to hold some of these methylphenidate dosages below the threshold of some of these negative symptoms, thereby increasing the tolerability of this common ADHD drug.
Zinc Inhibition of the Dopamine Transporter Protein: This may offer a further explanation as to why zinc is effective in boosting the effectiveness of methylphenidate. We have spoken extensively about the dopamine transporter ( DAT ) protein and its effects on dopamine levels and ADHD. Several ADHD medications, especially of the stimulant variety (such as methylphenidate), work by inhibiting or blocking DAT. It appears zinc may also act as a natural DAT inhibitor, thereby mimicking the effects of some of the more commonly used drugs.
In my previous post on zinc and its amplification of Ritalin's effectiveness, I wondered aloud as to whether zinc could be used as an outright substitute for the medication methylphenidate. While still a personal hypothesis, I still believe that for low level doses, zinc may be an ample natural alternative, but, this hypothesis obviously needs to be tested at a clinical level. Nevertheless, I personally believe it to be worthy of investigation.
Zinc as a possible treatment option for juvenile growth impairments: It is suggested that children with ADHD exhibit a delay in the overall growth process. We actually discussed this very topic in an earlier post titled: Do ADHD stimulant drugs stunt growth? Now it appears that zinc may possibly play a role in this. Using a primate model of zinc deficiency, Golub and coworkers found that zinc deficient monkeys showed a slowing of the growth process during what would normally be a period of growth spurt. If this translates into humans, then it is possible that underlying growth and attentional impairments, as well as abnormalities in activity levels (which is sometimes evident in children with ADHD, often more alongside those with the inattentive subtype of the disorder), may actually be due to zinc deficiencies.
Perhaps on an even more interesting note, the study found that "attention performance was also impaired before the onset of growth retardation". In other words, an attentional deficit may serve as a proverbial canary in the coal mine that a child may suffer from a subsequent delinquency in growth in the upcoming years. As a result, this blogger personally believes that some of these "attentional deficits" may not simply indicate an isolated case of ADHD, but rather serve as a warning of a much larger underlying problem that may be tied to a nutritional deficiency. Furthermore, it is at least possible that the underlying problem of attentional deficits and growth impairments in children with ADHD may be remedied by an intervention strategy that involves adequate dietary zinc or treatment via zinc supplementation.
Given that zinc deficiencies are common in both Western countries such as the U.K., as well as developing countries such as China it seems evident that ADHD symptoms may be part of a larger picture, a proverbial cry for help due to a widespread nutritional deficiency. In addition to ADHD, other disorders dealing with cognitive development may be susceptible to zinc deficiencies. Of course, a great deal of further study is needed to back up this assertion, but it leads us to wonder exactly how often a case of ADHD is actually due to something as simple as a deficiency in zinc or another common nutrient. We will have further discussions regarding this important mineral in future posts.