Horsetail Safety Questioned

Reference: Fabre B, Geay B, and Beaufils P: Thiaminase activity in Equisetum arvense and its extracts. Plantes Medicinales Phytotherapie 26: 190-197, 1993.

Summary: These investigators set out to study the properties of an enzyme called thiaminase from the herb Equisetum Arvense (Horsetail). This enzyme breaks down vitamin B1 and in animals has lead to the signs of vitamin B1 deficiency: spasm, loss of appetite and weight, ataxia, etc. Three different types of horsetail preparations were studied: a dry and fresh plant powdered extract of 1:1 and 1:3 ratio respectively, an aqueous (water) dry extract of 4:1 ratio; and a fluid extract of 1:1. The powdered plant extracts exhibited a potent anti-thiamine effect in vitro. In contrast, both the aqueous and the fluid extract had minimal or no anti-thiaminase action. Temperature of 100 degrees centigrade as well as alcohol and a pH of 8 to 9 all seem to inactivate the thiaminase enzyme.

Comments/Opinions: Horsetail (Equisetum arvense) has been used as a medicinal plant for its diuretic and anti-hemmorhagic properties. Horsetail is also rich in the trace element silicon and as such has an impact on the integrity and health of connective tissue throughout the body. Nor example, "French researchers have reported that the silicon content of normal human aorta decreases markedly with age and that the concentration of silicon in the arterial wall decrease with the development of atherosclerosis." Furthermore, because silicon affects cartilage composition, including articular cartilage, inadequate silicon nutriture may be of consequence in some joint disorders such as osteoarthritis."(1)

The recommended intake of elemental silicon is 5 to 10 milligrams per day. Interestingly enough, according to Drs. Seaborn and Nielsen, aging and low estrogen levels decrease the ability to absorb silicon. This could account for why silicon is another important ultra trace mineral necessary for the development and maintenance of a healthy bone.

Despite the benefits of silicon, not all forms of horsetail are safe for human consumption. It would seem prudent to suggest that infants, young children, and pregnant women not ingest this herb for any length of time unless the thiaminase enzyme has been deactivated. The onus is on natural product manufacturers to document their products' safety for public consumption.

(1) Seaborn C and Nieslen F: Silicon: A nutritional beneficence for bones, brains, and blood bessels? Nutrition Today 28: 13-18, 1993.

Natural Product Research Consultants, Inc.

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By R. Reichert

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