Thursday, July 22, 2010

Zinc!

When one makes a study of evolutionary medicine-type issues (that is, all chronic Western disease mediated by inflammation and diet and lifestyle so far removed from the life our bodies were designed for), the same nutrients keep popping up again and again. Fish oil is a good example. Yes, for heaven's sakes. I'm taking my fish oil. Shut up about it already.

When examining the small unexplored niche of nutritional evolutionary psychiatry, however, another trace mineral nutrient keeps bobbing to the top. This warrants a post, of course (or two, or three). Yup, no surprises here - I'm talking about zinc.

Let's start with the basics. This first bit of info comes from a rather abruptly titled "Zinc and depression. An update." from Poland in 2005. No cutesy titles in Poland! They get down to business. Good. I'm from Texas. I prefer cute yet vaguely threatening, myself (i.e. "Don't mess with Texas" as an anti-littering campaign - Also, driving out in the hill country, a large sign with scarecrow: "No trespassing. We don't call 911.") Gulp.

Zinc is a trace mineral (like magnesium, iodine, selenium, et al) that is essential for our continued life. Turns out that 300 or more enzymes in our bodies use zinc as a buddy to help them do their thing. DNA replication, protein synthesis, cell division - basic, mondo important, reliant on the presence of zinc. And guess what - the highest amount of zinc in our bodies is found in the brain - specifically in our hippocampus and cerebral cortex. Zinc deficiency can therefore lead to all sorts of unlovely consequences, such as ADHD, depression, alterations in behavior, learning, mental function, and seizures.

Turns out scientists of yore did all sorts of horrible tests on rats to figure out how zinc might be related to depression. Antidepressants seem to increase the ability of zinc to work as an anti-inflammatory agent in rat brains, zinc alone seems to be an antidepressant for rats, and the combination of zinc + small amounts of different classes of antidepressants (TCAs and SSRIs) enhanced the ability of the antidepressants to do their thing (helping the rats swim longer in hopeless situations, for example, or endure being held by their tails. Is reality TV really any different?).

Zinc therapy in rats also increases the amount of BDNF in rat hippocampi. Readers of the archives will note I am a big fan of BDNF in the hippocampus. And zinc reduced the fighting behavior of rats (and prisoners) too!

Yes, humans. Turns out Maes (my new hero - churned out a 62 page article on inflammation and depression this year, which I now have in my hot little hands!) discovered that zinc is low in the serum of humans with depression. Also, that low zinc seems to affect inflammation and immunity. Our T-cells (members of the immune system who hunt and kill infection) don't work well without zinc, and seem to release more inflammatory cytokines (IL-6 and IL-1) with low levels of zinc. Also, one of zinc's special actions is to inhibit the NMDA receptor in the brain. In suicide victims, there seems to be an alteration of zinc's ability to affect the NMDA receptor. (Turns out, BDNF + zinc helps calm down the NMDA receptor, leading to antidepressant effects.) Can zinc supplementation have antidepressant effects in humans? You may not be surprised at this point that the answer is yes (1).

There is more, much, much more to the story of zinc and psychopathology, but for now, let's end with good sources of zinc in our diets. Not surprisingly, the best sources of zinc are protein-rich meats, such as beef, pork, lamb, shellfish (especially oysters), chicken, turkey, etc. Pumpkin seeds are also a good non-meat source, and while grains have zinc, the absorption is strongly affected by the phytic acid in grains (2). Vitamin C, E, and B6 help you absorb zinc also. Seems that people with intestinal problems (celiac disease, inflammatory bowel), vegetarians, those with chronic kidney and liver diseases, alcoholics, and the elderly are most likely to suffer from zinc deficiency (3). Intake of more than 50mg a day (both from diet and from supplements) can lead to improper copper metabolism, altered iron function, reduction of HDL and reduced immune function.

More on zinc to come!

6 comments:

  1. The primal diet--something to smile about. ;-) Thanks for the informative post. I've been eating smoked oysters (canned in olive oil) a coupla times a week for the past year. Sardines on alternating days. And grass-fed beef, pastured lamb or chicken, and wild caught fish is a daily dinner in my household. Somehow, I'm having a dickens of a time trying to get my 4-year old to eat the beef/lamb/fish. She'll eat the chicken, but only if she can smear lots of avocado all over it, which even I think is sinfully delicious. She will also eat hot-dogs made from grass-fed beef, which I get a my local Sprouts supermarket. Forget about trying to get her to eat a single oyster. My 2-year old, however, will eat fish, chicken, and lamb. Yippee!

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  2. My one year old will eschew grains and eat just meat, dairy, veggies, nuts, fish, and fruits, bless her heart. The three year old asks for a jelly sandwich or pasta every day, but can be bribed to eat real food with the promise of dark chocolate in the evening. Like most toddlers she would prefer to drink milk alone! Whole of course!

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  3. Wow, two young kids. I don't know where you find the time to keep up such an informative and well-constructed blog! I'm guessing your 3-year old encountered SAD food before you started making the switch in your life to more primal fare. That's what happened in my case and my 4-year old (about to turn 5) loves pasta, rice, tofu, ice cream, and cake, and chocolate. At least I've gotten her to really enjoy 85% dark chocolate.

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  4. Hah! I consider this sort of thing to be "fun." (Yes, the older child knows SAD! I've only been paleo since the end of March. Whole real foods and avoiding vegetable oil for three years prior, but plenty of grains then.)

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  5. Zinc! My new obsession. Any info on postpartum, post breastfeeding depletion? Here's my story - just weaned my one year old and got hit with BIG TIME depression. I breastfed my first son 2 years and did not experience this. Also, I blew up overnight. Headaches, bloating, PMS symptoms. So I start Googling and come up with this theory:

    Nursing can cause zinc depletion.
    Maybe I did not feel the symptoms while I was breastfeeding because of the estrogen damping effects of nursing.
    Weaning caused my body to start producing mondo estrogen, but because I was zinc deficient not making enough progesterone to balance.
    Thus overnight bloat, PMS, depression, headaches.
    Taking some supplemental zinc has totally helped this problem!

    Still reading about the bounty of zinc - dopamine, leptin, insulin, HGH........

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  6. Weaning is a very common time for depression to rear its head. Zinc seems a logical culprit, but also you go from lots of oxytocin to little oxytocin and then those other hormonal changes - there are probably multiple culprits. I'm not aware of data on this, but I haven't looked too hard.

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