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Silica: Diatomaceous Earth vs Horsetail Grass

Silica is essential to the body, especially for the production of structural proteins including collagen and elastin. Structural proteins help give strength and elasticity to the hair, nails, bones, cartilage, tendons, ligaments, blood vessel walls, etc.

The body does not absorb and utilize silica in the form of silicon dioxide. Instead, silica reacts with water to form small amounts of orthosilicic acid (OA), which is absorbed by both plants and animals for the formation of tissues. Although OA is not “silica” (silicon dioxide) in the scientific sense it is still referred to as silica. Especially when referring to OA in plants.

The presence of acid increases the conversion of silica in to OA. In the body the primary acid source is stomach acid. Stomach acid declines with age though. This decreases the body’s ability to produce and absorb OA leading to loss of tissue integrity and elasticity frequently associated with “aging disorders”. The use of acid blockers or antacids such as acid heartburn medications, coral, dolomite, oyster shell or alkaline waters can further inhibit the production and absorption of OA.

Primary dietary sources in animals for OA include mineralized water and fibers. OA is formed in natural water sources as water dissolves small amounts of silica in soils and rocks forming OA. OA in water is also taken up by plants where OA helps to give plants strength by incorporating as part of their fibers. When these fibers are ingested the OA in the fibers can be extracted for use by the body.

Horsetail grass (shavegrass) is often incorrectly referred to as the highest herbal source of “silica”, as OA. The fact is that bamboo stalk is 7 times higher in silica than horsetail grass.

Diatomaceous earth (DE) is another excellent source of silica, and also contains much higher levels of silica than horsetail. DE is the skeletal remains of phytoplankton and consists of 80% silica compared to the average 4% silica content for horsetail grass.

As an herbalist I really do not recommend the use of horsetail grass as a silica source for several reasons:

  • Some species of horsetail are very toxic
  • Even the less toxic forms of horsetail grass can cause problems with long term use including nervous system disorders, headaches, loss of appetite and premature labor. In moderately high doses, or as a concentrate, horsetail grass can cause strong contractions of the blood vessels inhibiting blood flow to tissues.
  • Horsetail grass contains the enzyme thiaminase and the toxic alkaloid equisitine, both of which deplete thiamin from the body. Symptoms of thiamine deficiency include depression, lack of appetite, diarrhea, loss of muscle control, arrhythmias and tachycardia. Tinctures of horsetail pose even a greater risk as fresh plants are frequently used to make tinctures. Fresh horsetail contains higher level of toxic thiaminase and alkaloids. Thiaminase in particular is suspected in the poisoning of livestock ingesting horsetail grass. Although these poisonings are more likely due to toxic alkaloids, such as palustrine in horsetail grass, since ruminants can produce thiamine in the rumen.
  • Thiaminase has also been shown to be toxic to the liver.
  • Even though the amount of nicotine in horsetail is small, it does not take much nicotine to cause harm. Nicotine is one of the strongest central nervous system poisons known to man. It only takes 5mg to kill an adult human. To understand how small the amount really is needed to kill an adult consider the average single ‘O’ capsule normally used for capsuling herbs holds an average of 500mg. Because nicotine is also a powerful constrictor of blood vessels much lower levels can still be especially dangerous for some individuals. People with poor circulation to begin with such as diabetics, people with heart disease/failure, people with hypothyroidism and people with Raynaud’s disease or Raynaud’s phenomena are all more prone to the dangerous blood vessel constricting effects of horsetail grass.
  • Horsetail grass is contradicted with the use of diuretics to prevent abnormally low potassium levels and stimulants like caffeine to prevent over stimulation of the nervous system.

It is not clear if nicotine is the only component in horsetail grass that constricts the blood vessels. Other alkaloids present in horsetail may also contribute to this effect.

As an example of this effect a friend of mine was a fitness trainer in excellent shape. After drinking 2 cups of horsetail tea she went to bed. She woke up shortly afterward ice cold because the horsetail grass tea had constricted her blood vessels decreasing her blood flow.
If a herbal source of silica is desired the best choice is bamboo stalk, which unlike horsetail grass dilates blood vessels. This makes bamboo a much safer choice for people with high blood pressure, conditions that reduce circulation or that are on contradicted medications.

Other safe sources of silica include nettle leaf, oat straw and seaweeds.

A better choice though is food grade DE. DE is higher in silica than herbs and does not contain any toxic enzymes or alkaloids as in the case of horsetail grass.

Silica is poorly absorbed, but there are ways to increase levels in the body, even when stomach acid is low. A simple method is to add a spoon full of food grade DE to a gallon of water and allow the DE to settle to the bottom. This may take a few days initially. Pour the water you intend to drink from the top of the container, but be careful not to disturb the DE on the bottom of the container. Refill the container with water and allow it to settle out again. Keep repeating this process. A spoon full of DE should last several years if it is not poured off in the water.

There are several advantages to this method. First of all, small amounts of the silica in the DE are dissolved in to the water every time new water is added forming OA. Secondly, because silica is poorly absorbed only a fraction of the silica from silica supplements will be absorbed. In addition, people will not take silica supplements as often as they will drink water each day. Adding the silica to water results in the formation of OA of which small amounts are absorbed each time a drink of the water is taken. This leads to significantly higher levels of OA absorption from drinking the water throughout the day compared to taking an occasional silica supplement.

Is DE Toxic?

Anything can be toxic is sufficient quantities or if used improperly. DE is only toxic though if inhaled repeatedly over long periods of time, which can lead to silicosis. This is actually a potential problem with other silica sources as well such as clays, which are formed from the weathering of silica containing rocks. Ingested DE has not been shown to be harmful though. In fact, DE has a long history of use in silica supplements and being ingested to eliminate intestinal worms in animals and people with no adverse effects.

The reason DE kills intestinal worms without harming the intestinal wall is simple. Intestinal worms have much thinner and delicate tissues than the human digestive system. Worms therefore are prone to the abrasive effects of DE, unlike the human gastrointestinal tract. In fact, DE is considerably less abrasive than the fibers we ingest in our diets, which are less abrasive than horsetail grass. Horsetail grass is so abrasive that it is also known as scouring rush for its use in the pioneer days to clean pots and pans.

DE is only slightly abrasive being more like ultrafine sandpaper used for polishing. For this reason it is commonly used in toothpaste to safely clean teeth.

Other common uses of DE are:

• Insect control in foods we consume.
• As an anti-caking agent in foods.
• An addition to animal feeds to keep livestock worm free without toxicity.
• In cosmetics as a filler, opacifier and scrub agent since DE is not toxic and it will not harm the skin.
• As an additive to some soaps.
• As a flow agent and filler for the manufacturing of capsules and pills since it does not harm the digestive tract.

Myths About DE

Myth: DE is “agatized” silica and has a hardness of 7 on the Mohs hardness scale making it hard on the tissues.

Fact: This false claim is based on the hardness of pure silica, which has a hardness of 7. DE is not pure silica though. It is comprised of 80% silica, 10% metal oxides and 10% moisture. The actual hardness of DE is actually quite low, 1 to 1.5 on the Mohs hardness scale, which runs from 1 (the softest) for talc to 10 (the hardest) for diamond. This can be verified on this link showing the hardness for various materials on the scale:


Another way to look at this is bentonite clay is a weathering byproduct of rocks, and like DE contains silica and smaller quantities of other minerals. Despite the content of silica, bentonite has nowhere near a hardness of 7.

As for the claim that DE is agatized silica, again this is not true. Agate is formed from extremely hot water supersaturated with silica, and possibly some magmatically dissolved silica. This dissolved silica deposits in to crevices or vugs within rocks or replaces organic matter in items such as shells or wood creating layers of hard silica.

Again, DE is the skeletal remains of phytoplankton that have died and settled to the bottom of ancient oceans and lakes. These phytoplankton, nor their remains, were ever subjected to extremely hot water or magma to dissolve the silica and redeposit it as a quartz such as agate.

Food grade DE is extremely soft having a hardness of 1-1.5, as pointed out earlier, far below the hardness of pure silica that has a hardness of 7. In addition, food grade DE consists of amorphous, not crystalline, silica. Amorphous silica is not as hard and sharp like crystalline silica and does not pose the same health risks as crystalline silica.

Clumps of DE are also sold as kitty litter. If DE was so sharp and hard as claimed, cat’s paws would be shredded from scratching in the litter box. Of course this is not the case since the claims about DE being hard and sharp to the point of damaging tissues are simply untrue.

Myth: Consuming silica causes kidney damage.

Fact: I have heard people claim that they got kidney pain within minutes of ingesting DE. It is hard to say why they experienced this problem, but it was not from the silica in the DE as I have seen claimed. A simple fact of anatomy and physiology can prove this. Once ingested, the silicon dioxide in the DE has to convert in the stomach in to OA in order to be absorbed. When the stomach finally empties its contents in to the in intestines the OA can be absorbed. Next the OA circulates through the blood where most of the OA is utilized in the formation of tissues. Finally traces of OA can reach the kidneys for safe excretion. No damage occurs to the kidneys since the OA is not in a solid crystalline form that can cut thinner tissues of the kidneys. The whole process for the traces of OA to be absorbed and even smaller traces to reach the kidneys takes considerably longer than the few minutes people are claiming to get pain within.


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