What Are the Dangers of Comfrey?
Comfrey is has been used through the ages as a healing herb for various ailments of the digestive track and broken bones. In modern times, information about the plant has caused concern over some of the chemicals contained in comfrey. Although the results have been debated, after much research, it has been proven that comfrey contains compounds which harm the liver.
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What Is It?
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A flowering herb with bell-shaped pink, white, blue, or purple blooms. Comfrey has long been used as a garden fertilizer in compost due to its easy and hardy reproducibility. Resembling a turnip in shape, comfrey roots are black in color externally and white and juicy on the interior. The plant can reach 2 to 5 feet in height. Typically, the leaves can be harvested as many as five times per the growing season of spring and summer. Comfrey is native to Europe, especially Great Britain, and some parts of western Asia and is also grown in North America.
Toxicity
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It has been known since the 1960s that comfrey contains pyrrolizidine alkaloids (PAs) which are toxic to the liver and can cause liver damage, cancer, and death. In July of 2001, the FDA banned the internal use of comfrey and all dietary supplements of this herb were pulled from shelves. Other countries that ban internal use of comfrey are Great Britain, Canada, Germany, and Australia. Some proponents of comfrey challenge the study "The Carcinogenic Activity of Symphytum Officinale" by Hirono, Mori, and Hago (Japan, 1978) which sparked the U.S. legislation regarding the use of comfrey. Proponents feel that a segment of the research results which focused on injecting newborn rats with PAs was unrealistic in comparison to human adults. Nonetheless, several studies have been published since which support the findings of Hirono, et al.
Cancer Link
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Comfrey contains lasiocarpine. Lasiocarpine is a hepatoxin (liver poison) and a carcinogenic member of the PA family. It interferes with RNA and DNA synthesis within the liver cells. Largely, this information is from the study performed in 1978. Rats ingested comfrey in amounts multiple times their body weight on a daily basis for 1.5 to 1.75 years, and, at the end of the experiment, all the rats in the comfrey group developed a type of tumor known as adenoma, which is a benign growth. Hemangiosarcomas, easily metastasized vascular malignant tumors, were seen infrequently in the comfrey rats. The control group did not develop tumors of any type.
Liver Disease
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The PAs in comfrey cause cell enlargement in the liver, often three times the size of normal liver cells. An enlarged liver is a fundamental diagnostic tool in liver disease. Lacarpine also causes congestion in the liver due to blockage of veins and other sinus cavities. Additionally, PAs have been known to negatively affect metabolic processing of vitamin A, reducing circulating levels in the blood. Vitamin A is required for healthy vision, skin, bone, and supports the immune system.
Conclusions
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The safety of ingesting comfrey is too questionable to gamble one's health. Nearly all the research supports the early study in 1978 that comfrey has carcinogenic and hepatoxic side effects. Although, applying externally as a poultice to unbroken skin is still considered safe and beneficial. Comfrey contains allantoin which has healing properties for the bones and skin. However, even externally, no more than 10 micrograms of PAs should be applied on a daily basis.
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