Sulfites
in Chinese Herbs
Sulfur dioxide is one of the
standard preservative agents used in the Chinese herb industry. Preservatives
can be categorized into three general types: antimicrobials that inhibit
growth of bacteria, yeasts or molds; antioxidants that slow oxidation
of fats and lipids thus slowing the rate of rancidity; and a third type
that blocks the natural ripening and enzymatic processes that continue
to occur in foodstuffs after harvest.
Sulfur dioxide serves all three functions, which is one reason why it and related compounds called sulfites are found in so many household products. Sulfur dioxide is a pungent, colorless gas formed when mined sulfur is heated. For hundreds of years, sulfur dioxide and more recently chlorine and aluminum phosphates have been used on Chinese herbs to prevent mold and insect infestation, to bleach the color of the herbs, and as a fumigant.
When sulfur dioxide comes into contact with a liquid, such as water or wine, it changes into sulfites. While we are not aware of sulfites in their solid, powder form being used directly on dried Chinese herbs, when sulfured herbs are used to prepare soups, herbal teas, extracts, pills and tablets, etc., sulfites become concentrated in the resulting liquid or end product. Unknown to most herb suppliers, manufacturers, and practitioners, sulfured herbs may also change the herbs energetic nature and can affect the efficacy of a formula.
Dairy, wine, and fruit products that contain sulfites or that are treated with sulfur dioxide are required to disclose this on their packaging. Unfortunately, this requirement does not apply to traditional Chinese herbs. In fact, herb distributors who consider their herbs completely natural may be unaware of the high amounts of sulfur dioxide used to preserve and whiten their herbs during processing.
Between five and ten percent of Americans are at least slightly allergic to sulfites. Reactions include breathing difficulties, hives, headaches, and sinus congestion. 0.4% of Americans are highly allergic to sulfites and can suffer more acute symptoms, even from very low levels. Sulfites can be particularly detrimental to individuals who suffer from asthma.
Although most people are not allergic to sulfites, sulfite sensitivity can develop at any point in life. No one knows what triggers onset or the mechanism by which reactions occur. Doctors believe that asthmatics develop difficulty breathing by inhaling sulfite fumes from treated foods. Asthmatics who have more severe symptoms and are dependent on corticosteroids are especially prone to sulfite sensitivity and are most at risk of having a severe reaction. However, it's a chicken-and-egg situation. It is unknown whether asthma causes sulfite sensitivity or vice versa, as some people's first experience with asthma is a sulfite reaction, and as their asthma becomes more severe they may eventually become steroid-dependent.
The deleterious effects of the sulfuring process on the health of workers involved in the processing is gravely concerning; as are the environmental impacts of the sulfuring process itself. Inhalation of sulfur dioxide fumes burns the lungs, and health impacts such as death and respiratory failure can be both immediate and cumulative.
On an environmental scale, when sulfur dioxide comes into contact with water, besides sulfites, a variety of sulfurous acid salts form: sulfurous acid, bisulfite ions and sulfite ions. In nature, these acid salts are formed when erupting volcanoes cause sulfur dioxide to escape into the atmosphere and come into contact with moisture and clouds. Unfortunately, this contributes to the formation of acid rain, one of the most prevalent and destructive forms of pollution in our environment. The sulfuring process of herbs is the same process on a much smaller scale, but is ongoing and serves to add to the accumulation and spread of acid rain in our environment.
TCM perspective on sulfur
Technically, according to traditional Chinese herbal sources, the medicinal properties of sulfur are Sour, Hot and Toxic. Medicinal plants which should be Sweet become Sour when treated with sulfur dioxide. As taste is an important indicator of function in Chinese medicine, there is a potential for sulfur dioxide to compromise the intended action of the herbal ingredients. The Hot, Toxic nature of sulfur also raises questions regarding its use and effects within medicinal formulations. In addition, sulfur's sour taste makes the herb's taste even less palatable for your patients, making compliance more difficult.
Sulfur dioxide serves all three functions, which is one reason why it and related compounds called sulfites are found in so many household products. Sulfur dioxide is a pungent, colorless gas formed when mined sulfur is heated. For hundreds of years, sulfur dioxide and more recently chlorine and aluminum phosphates have been used on Chinese herbs to prevent mold and insect infestation, to bleach the color of the herbs, and as a fumigant.
When sulfur dioxide comes into contact with a liquid, such as water or wine, it changes into sulfites. While we are not aware of sulfites in their solid, powder form being used directly on dried Chinese herbs, when sulfured herbs are used to prepare soups, herbal teas, extracts, pills and tablets, etc., sulfites become concentrated in the resulting liquid or end product. Unknown to most herb suppliers, manufacturers, and practitioners, sulfured herbs may also change the herbs energetic nature and can affect the efficacy of a formula.
Dairy, wine, and fruit products that contain sulfites or that are treated with sulfur dioxide are required to disclose this on their packaging. Unfortunately, this requirement does not apply to traditional Chinese herbs. In fact, herb distributors who consider their herbs completely natural may be unaware of the high amounts of sulfur dioxide used to preserve and whiten their herbs during processing.
Between five and ten percent of Americans are at least slightly allergic to sulfites. Reactions include breathing difficulties, hives, headaches, and sinus congestion. 0.4% of Americans are highly allergic to sulfites and can suffer more acute symptoms, even from very low levels. Sulfites can be particularly detrimental to individuals who suffer from asthma.
Although most people are not allergic to sulfites, sulfite sensitivity can develop at any point in life. No one knows what triggers onset or the mechanism by which reactions occur. Doctors believe that asthmatics develop difficulty breathing by inhaling sulfite fumes from treated foods. Asthmatics who have more severe symptoms and are dependent on corticosteroids are especially prone to sulfite sensitivity and are most at risk of having a severe reaction. However, it's a chicken-and-egg situation. It is unknown whether asthma causes sulfite sensitivity or vice versa, as some people's first experience with asthma is a sulfite reaction, and as their asthma becomes more severe they may eventually become steroid-dependent.
The deleterious effects of the sulfuring process on the health of workers involved in the processing is gravely concerning; as are the environmental impacts of the sulfuring process itself. Inhalation of sulfur dioxide fumes burns the lungs, and health impacts such as death and respiratory failure can be both immediate and cumulative.
On an environmental scale, when sulfur dioxide comes into contact with water, besides sulfites, a variety of sulfurous acid salts form: sulfurous acid, bisulfite ions and sulfite ions. In nature, these acid salts are formed when erupting volcanoes cause sulfur dioxide to escape into the atmosphere and come into contact with moisture and clouds. Unfortunately, this contributes to the formation of acid rain, one of the most prevalent and destructive forms of pollution in our environment. The sulfuring process of herbs is the same process on a much smaller scale, but is ongoing and serves to add to the accumulation and spread of acid rain in our environment.
TCM perspective on sulfur
Technically, according to traditional Chinese herbal sources, the medicinal properties of sulfur are Sour, Hot and Toxic. Medicinal plants which should be Sweet become Sour when treated with sulfur dioxide. As taste is an important indicator of function in Chinese medicine, there is a potential for sulfur dioxide to compromise the intended action of the herbal ingredients. The Hot, Toxic nature of sulfur also raises questions regarding its use and effects within medicinal formulations. In addition, sulfur's sour taste makes the herb's taste even less palatable for your patients, making compliance more difficult.