As I was hiking up our mountain the other morning I came upon a beautiful patch of Horsetail growing on a hill by the side of the road. I bent over and sang to it, while harvesting some of the young shoots. As I turned to run down the hill with my basket of harvest, I ran into a woman from town who asked me about what was in the basket. I told her, in short, most of what I said here, then I quickly ran home to lay the herb on screens so that they would dry properly and retain their minerals. It was lovely to impart some Horsetail wisdom onto someone else, and I felt inspired to continue talking about it to people throughout most of the day.
Then, a few days ago, that same woman came in to my store and asked me if Horsetail was poisonous. I told her that it could be toxic if the matured plant was picked late in the season, but besides that I knew of no other dangers it could pose. She then told me that she read that it contained nicotine and inhibited the body's ability to absorb Vitamin B-1, or Thiamine. These were good questions, so I told her I would look into it and write something on it this week.
Let's first discuss the concern of vitamin B deficiency caused by Horsetail. Thiamine (B-1) is a crucial vitamin that helps the body transfer carbohydrates into glucose, which then allows the nervous system to function properly. Without it, we develop a condition known as "beriberi" which manifests as overall weakness, mental confusion, body pains, tingling in the fingers, and other symptoms of a damaged nervous system.
Horsetail contains an enzyme known as "Thiaminase" which breaks down the Thiamine molecule into two parts, rendering it obsolete to the body. Thiaminase, like most enzymes, is destroyed by heat, alcohol, and other forms of processing. Mussels, scallops, carp, and many other wild aquatic foods contain Thiaminase, but pose no threat if cooked properly. Horsetail should never be eaten, only extracted. Whether it's tinctured in alcohol, or infused by boiling into water, herbal extracts of Horsetail should have no Thiaminase present due to the enzyme destroying properties of the heat, or alcohol, that processes them into medicinal formulas.
Horsetail is toxic to cattle and horses who graze in pastures abundant with fresh shoots, or who eat hay that have dried shoots of Horsetail mixed into it. Though there has never been one case of Horsetail toxicity in humans, the alarm was sounded due to the widespread toxicity in these animals. It is important to understand that these animals were eating raw or dried Horsetail, not taking Horsetail tinctures or infused teas. The mainstay of their diets were made up of raw Horsetail shoots rich in Thiaminase, unlike a small percentage of our diets made from Horsetail tea or tincture.
The second reason of concern was that Horsetail contains nicotine and, as we know, nicotine can be toxic and addictive. It is true that Horsetail contains nicotine, but less than 1 part per million, which is .00004% of its entire volume. Once again, heating, picking the plant early, and other processing factors can possibly rid all, or most, of the minute nicotine content from the final product. When you compare the miniscule amount of nicotine in Horsetail to that of common, everyday foods you can see there is little to worry about.
Tomatoes and peppers have 7ng (nanograms) of nicotine per gram of tomato, potatoes have an avergae of 15ng per gram, cauliflower has 16ng of nicotine per gram, and eggplants have a whopping 100ng per gram - the highest concentration next to tobacco. The latter is interesting because this study suggests that nicotine may help improve memory, protect neurons, and stimulate the brain. I'm certainly not advocating nicotine patches, but I find it interesting that they are claiming nicotine to be beneficial for memory and, at the same time, many studies have found that eggplants can prevent Alzheimer's.
A cigarette contains 9mg of nicotine, in comparison to a tomato that has 32ng of nicotine. To understand how small a nanogram is, consider that there are one billion of them in one gram. This poses little to no threat to your nervous system or body.
In conclusion, I believe Horsetail is a safe herb to use for urinary health, bone health, skin health, and overall body mineralization. If you feel it is unsafe, simply stay away from it. If you want to use it, but still feel concerned, use it for six weeks then discontinue for eight weeks before using again. This way you can still absorb the plentiful silica and other complementary minerals, while avoiding too much of the nicotine or Thiaminase that may, or most likely may not, be present.
Lastly, most plants and teas have natural detoxification, diuretic, and liver cleansing properties. The minute amount of questionable compounds in them would surely be outweighed, and quickly eliminated, by the massive mineralizing, detoxifying, and diuretic properties natural to these herbs.
I drink from thee.
Give my bones strength,
Make my skin clean,
I invoke thee.