Tuesday, February 28, 2012

Zinc Deficiency and Children with Autism

Thanks to a commenter for pointing me to a newish study (open access):  Infantile zinc deficiency: Association with autism spectrum disorders.

I see Paul Whiteley already covered it here.  If you are interested in the autism spectrum disorders, I very highly recommend his blog.  Paul is very sober and clear-sighted about the limitations of the research information but has an open mind about what might be clues to the pathophysiology of these disorders.  Since it is a long paper, and Paul and I have quite different styles, I think there is plenty of room for my own thoughts.

Atlas Genius:  Trojans (right click to open in new tab)

In this study, nearly 2000 children with autistic disorders had hair tested for zinc deficiency.  584 (29.6%) subjects had levels lower than two standard deviations below the mean of the reference range.  43.5% of the male children ages 0-3 and 52.5% of the female children 0-3 in the sample were zinc deficient.  Older children with autism in the study had a lower incidence of zinc deficiency, which continued to decrease with the age of the subject sample, to the point where autistic children over the age of 10 had normal zinc levels.  Normal hair zinc in healthy children appears to be around 130 ppm, and one autistic 2 year old in the study had a level of 10.7 ppm.

However you slice it (and let's take into account the limitations of a strictly observational study), that is an impressive finding.  The authors speculate that epigenetics could be a factor in the pathophysiology of autism.  Epigenetics is the alteration of gene expression by environmental influences.  Mineral deficiencies could certainly alter gene expression and perhaps cause an epigenetic disorder.  The other side of the argument is that active inflammation and stress causes us to waste zinc (and other minerals) as part of the inflammatory process.  Since we know autistic spectrum disorders are related to inflammation, it would make perfect sense that babies and toddlers with autism would have low zinc levels.  Low serum zinc also seems to be associated with heavy metal toxicity, which is also associated with autistic spectrum disorders (more often cadmium and aluminum, according to the study authors, than mercury).

But measuring a mineral deficiency is more tricky than it might appear.  Zinc can be sequestered in the bones or liver and bound up by protein in the serum.  Zinc levels can vary considerably based on infection, stress, low protein levels in the blood, and even time of day.  Hair levels could perhaps be considered a more reliable indicator of full-body zinc stores, so may be a more useful measure for these sorts of studies.

Zinc deficiency could very plausibly be part of what causes the symptoms of autism.  Zinc plays an important role in protein synthesis, cell growth and repair, and levels need to be super topped off in pregnant women and infants where all these processes are occurring at a more rapid rate than any other time in one's life.  Also, we know that a "leaky gut" has been associated with autism in a rather well-designed study, and with leaky guts there is malabsorption of nutrients and minerals.  Many children with autism have signs from birth (when everyone has a leaky gut, up through 6 months of age when there is no argument that exclusive breastmilk is best, period), but some children seem to develop normally and do not exhibit symptoms until later.  Could leaky guts leading to toxin exposure, and micronutrient deficiency have something to do with these cases?  Seems a plausible theory.

In addition, in the setting of zinc deficiency, the intestinal zinc importer (the awesomely named Zip4) is upregulated, sensibly enough.   Increasing Zip4 can increase the absorption of toxic heavy metals such as cadmium and lead.  Therefore an early zinc deficiency could plausibly lead to more absorption of toxic metals.   (Creepy fact from the article:  soy-based infant formulas have 6 times higher cadmium levels than cow's milk formulas, and cereal-based formulas 4-21 times higher levels (1).)

I don't think there is any argument that we all need sufficient zinc, particularly pregnant women and babies.  As far as I know, there are no controlled studies of zinc supplementation in pregnant women and babies and autism risk, so we really can't make any conclusion or recommend any sort of increased zinc supplementation in babies at this point.  There is more data in ADHD and I should probably pull those papers myself (some of them are too old to pull easily) and do a post on it.  Super-high zinc intake has killed older people who used zinc-based denture cream by causing copper deficiency and heart arrhythmia, and babies and little children (like the elderly) will be more vulnerable to these sorts of insults.

More data please!  Researchers, rescue us from the rocky shoals of the unknown.

(Hmmm.  My favorite diaper cream is zinc-based.  I wonder how much is absorbed and if that has any bearing on zinc levels, zinc deficiency, etc.)




6 comments:

  1. Thanks for posting this. I am constantly amazed at the huge number of conditions that are increasingly considered to have an epigenetic base. Bad news - we're doing it to ourselves. Good news - we can STOP. :)

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  2. Zinc is extremely important to prenatal development.

    In reproductive aged females, zinc deficiency will lead to adaptive amenorrhea by suppressing leptin synthesis, the same as deficiency of total calories and body fat or excessive stress (all of these are obviously bad signs for reproducing at that time).

    I wonder if avoidance of animal food correlates with risk of autism? If zinc deficienc is an etiological factor, then it will, as zinc is primarily found in protein food (which is also crucial for proper prenatal development).

    Kind of an ironic follow up to the previous entry where a couple of idiots argue that eating meat = being stressed and tense!
    Factoid: humans need animal food to thrive.

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  3. What is it about the phrase "my favorite diaper cream" that gives me pause?

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  4. Our daughter was diagnosed with High Functioning Autism at the age of 2. I can't speak for her zinc levels, but after starting her on a Paleo diet, we saw an immediate improvement in her socialization, particularly eye contact. Our theory is that she was had nutrient deficiency and definite Leaky Gut. She just turned 4 and we continue to keep her diet very clean and nutrient-dense as her symptoms improve. Thank you for this post.

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  5. I just started reading your blog. So far I have enjoyed it immensely (both for post content and soundtrack). I thought this song by Of Montreal (Heimdalsgate Like A Promethean Curse) might be suitable for your soundtrack one day if it is not included on it already.

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  6. There is a condition called pyroluria which is actually not recognised by mainstream medicine (yet treated by many trained MDs, GPs etc) that results in a zinc deficiency, copper excess and B6 deficiency. The doctors that are trained in this field (see biobalance.org.au for more information) have identified that many children with autism who have been tested via urine for the pyroluria marker (kryptopyrrole) do indeed have elevated kryptopyrroles which are the substance that binds to zinc and B6 and excrete them from the body, leaving the individual low in those.

    It's tragic that this condition is not recognised - I have personally had great improvements in my health by treating my zinc:copper imbalance (that results from pyroluria) - no more extreme noise and light sensitivity (which is common in autistic people) and I reversed an igG subclass immune deficiency.

    Zinc is needed in 200+ metabolic reactions in the body, so if there isa frank deficiency or if there is too much copper in balance with zinc, then it stands to reason that the individual will have far reaching health problems - mental, behavioural and physical.

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