Sunday, November 14, 2010

Selenium!

Some of my most popular posts are about the minerals (exclamation point) and I'm guessing this one will be no exception. My least popular/commented upon posts are about ADHD. Not sure why. ADHD is way more common than say, schizophrenia. But I will give my readers what they want! Even though I don't get paid for the blog. Something is wrong with my business model here. I need to be more like those paleo entrepreneur geniuses with 4 hour work weeks and yachts.

So - selenium. This is a micronutrient found in the soil and in marine bivalves, and fixed by plants into more organically bioactive forms. Levels are extremely high in certain parts of China, Turkestan, and the Western United States. Levels are quite low in Finland, Scotland, New Zealand, and other parts of China, so that livestock must be supplemented or will fall ill. (1). According to some gardening message boards, soils here in New England aren't great, and Texas where I grew up is rather middling. And according to the various selenium sources, it is somewhat difficult to figure out how much you do get from the soil, as areas vary widely and many forms of selenium are more bioavailable than others.

What does selenium do? Well, selenium is key to one of the body's master antioxidants, glutathione peroxidase. This complex keeps the delicate polyunsaturated acids in our cell membranes from getting oxidized (rancid).

Selenium deficiency has been described in China as Keshan Disease, a type of heart problem (2). It is also thought to be a factor in gastrointestinal cancer, liver cancer, and prostate cancer. In addition, selenium in concert with iodine seems to be important to thyroid hormone production (specifically in the conversion of T4 to T3). As I've mentioned before, selenium deficiency seems to be one of the major dangers of a carelessly designed ketogenic diet, leading to death via cardiomyopathy and arrhythmia in children. Selenium deficiency was also deemed the cause of death (via cardiomyopathy) of adult patients on selenium-deficient TPN (total parenteral nutrition).

Selenium is a trace mineral. Appropriate amounts for humans are measured in micrograms rather than milligrams. People have died (from hypotension and cardiac muscle depression) via the ingestion of gram amounts of selenium, and toxicity occurs at milligram amounts. Sources indicate that the first symptoms of toxicity are hair and nail brittleness and garlic smell on the breath. The cases of death I read about involved the ingestion of "gun bluing" (2% selenious acid), so don't drink gun bluing, as selenium posioning sounds like one of the more horrific ways to die.

The bioavailability of selenium is best in plant-derived foods (grains, actually) and nuts, while the selenium in animal sources, marine sources, and mineral waters aren't as bioavailable. Fruits and vegetables, however, don't seem to have that much in the US, so if you avoid grains, the best sources are actually brazil nuts (one ounce will get you over 500 micrograms, so take it easy and have just a few at a time). Organ meats are also high in selenium. 3 oz or so of tuna, beef, cod, and chicken breast will get you around 30 mcg (though it is less bioavailable), whereas a typical grain meal (pasta, oatmeal) will net you around 10-15 mcg. Though phytic acids in grains do interfere with mineral absorption, studies of women eating wheat from selenium-rich soils showed a nice elevation in plasma levels of selenium.

The adult US RDA is 55 micrograms (though a bit higher for pregnant or breastfeeding women). (3)The doctors Jaminet recommend 200 mcg daily, and the US upper tolerable limit is 400 mcg (the level above which those nails start to get brittle, you get irritable and tired, and that breath begins to be garlicky.). On the other hand, Chinese studies of daily doses up to 1500 micrograms showed no adverse effects, nor did another study of 600 mcgs daily.

In my next post I'll review the studies of selenium and mental health. In the mean time, eat a few brazil nuts and cool it on the supplements if your breath gets garlicky or your nails start to look like this. (Actually, go see a doctor pronto if your hair falls out and your nails look like that.)

(another iPad post so forgive any bad spelling, and I'll add a few more links later!)

7 comments:

  1. Woohoo! Selenium! Big fan of selenium. Sorry for the overexuberance, just darn excited to see another mineral post. Ever since going primal, my nails are no longer brittle. So despite eating a lot of oysters, duck liver pate, and beef, I'm probably not overdoing the selenium. Good to know the symptoms though. Looking forward to reading your views on the connection between selenium and mental health.

    ReplyDelete
  2. I'm beginning to see a pattern here, people have turned to grains for their daily supplement of selenium, magnesium, B vitamins. Minerals that would otherwise be 'hard' to get.

    With depleting our soil and refining our flour, the negative aspects of grains are greater the positive aspects.

    Paleo nutrition is a solution (stop the grains and return to organ meats and nuts) but also returning to whole/organic foods is a solution.

    See, both Paleo's AND whole/organic food vegetarians are partly right at the same time...

    Most people actually DO initially look/feel better after a they drop all meat/grains and turn to fresh organic greens and smoothies for a few weeks.

    ReplyDelete
  3. Selenium and iodine!

    Deficiency in one and excess of another can cause trouble.

    We all know of the increase in incidence of Hashimoto thyroiditis in coutries that have begun to supplement iodine, most of them deficient in selenium also. My country, Brazil, was one of them:

    http://www.ncbi.nlm.nih.gov/pubmed/11708308

    And we already know one country (Zaire) deficient in both that begun supplementing selenium:

    http://www.ncbi.nlm.nih.gov/pubmed/2045471

    Iodine and selenium go hand in hand:

    http://www.ncbi.nlm.nih.gov/pubmed/20517655
    http://www.ncbi.nlm.nih.gov/pubmed/20453397
    http://www.ncbi.nlm.nih.gov/pubmed/19689065
    http://www.ncbi.nlm.nih.gov/pubmed/19175172
    http://www.ncbi.nlm.nih.gov/pubmed/19035182
    http://www.ncbi.nlm.nih.gov/pubmed/17828501
    http://www.ncbi.nlm.nih.gov/pubmed/17484205
    http://www.ncbi.nlm.nih.gov/pubmed/17159829
    http://www.ncbi.nlm.nih.gov/pubmed/17044649
    http://www.ncbi.nlm.nih.gov/pubmed/17028378
    http://www.ncbi.nlm.nih.gov/pubmed/16943608
    http://www.ncbi.nlm.nih.gov/pubmed/16758970
    http://www.ncbi.nlm.nih.gov/pubmed/16598934
    http://www.ncbi.nlm.nih.gov/pubmed/16484530
    http://www.ncbi.nlm.nih.gov/pubmed/8427203

    ReplyDelete
  4. Selenium is another of the minerals that, if you look at your diet (alone), chances are you are not taking in even close to the RDA/RDI.

    Brazil nuts are rich in selenium, but you get a lot more selenium from unshelled nuts (you shell them then eat them). If you buy them already out of the shell, as I understand it the selenium is much reduced. Brazil nut trees are old and have huge root systems, and reportedly this results in absorption of radioactivity which gets to the nuts. So, I have seen suggestions that you not eat too much in the way of Brazil nuts for that reason. One unshelled nut a day is a good supplement.

    ReplyDelete
  5. Just a quick vote for more articles about ADHD!

    ReplyDelete
  6. Hi Aaron - Most nutrition is familiar to me from the elementary classes I took in college and the biochemistry and pathology from med school - but minerals were left out. So it's neat to go back and learn about them.

    Mario - lots to look through! Thanks for the links. I have some other links from you I need to sort through too on the thyroid. I think selenium and iodine is a natural bridge to thyroid discussion.

    Barkeater - my father has a Geiger counter. Maybe I'll have him test the brazil nuts over the holidays.

    MB - okay! More upcoming!

    ReplyDelete
  7. hi Emily
    I like ADD posts, don't give up on them

    ReplyDelete