Understanding the Different Forms of Indigo
The term “indigo” refers to a blue dye, but it can be derived from various sources, each with a distinct safety profile. The three most common forms are synthetic indigo carmine (used in food), certain medicinal plant extracts, and unprocessed or toxic plant species. Confusing these different types can have serious health consequences.
Indigo Carmine (FD&C Blue No. 2 or E132)
Indigo carmine is a synthetic food dye created in a lab, not derived directly from plants for this purpose. It is approved for use in the food and pharmaceutical industries to provide a blue color in certain products like confections and coatings. Regulatory bodies such as the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) have established maximum permitted levels for its use. While considered safe at these controlled levels, the ingestion of indigo carmine has been associated with adverse effects in some individuals. Reported side effects can include nausea, vomiting, and diarrhea. It is crucial to understand that the approval for food use applies specifically to this highly purified synthetic compound and not to other forms of indigo.
Plant-Based Indigo Extracts (Herbal and Medicinal Use)
Historically and in certain traditional medicine systems, indigo has been used for medicinal purposes. The herbal preparation known as Indigo naturalis or qing dai, derived from plants like Baphicacanthus cusia or Strobilanthes formosanus, has been used in Traditional Chinese Medicine. This preparation has been studied for its potential in treating conditions like psoriasis and ulcerative colitis. However, this is not the same as consuming raw indigo plant matter.
Several studies and case reports have highlighted significant safety concerns with oral indigo naturalis. Adverse reactions reported include reversible liver dysfunction, gastrointestinal distress (abdominal pain, diarrhea, colitis), and in rare cases, pulmonary arterial hypertension. The safety of these plant extracts is not fully established, and they are typically used under the supervision of a healthcare professional. Unprocessed or improperly prepared plant material should never be consumed.
Wild and Toxic Indigo Species
Not all plants that contain or are named indigo are created equal. Some species are explicitly toxic. Baptisia tinctoria, or 'wild indigo,' is considered likely unsafe when taken orally, especially in high doses, and can cause severe side effects such as vomiting and diarrhea. Similarly, the species Indigofera spicata (formerly I. endecaphylla) is known to be poisonous and has caused livestock deaths due to the presence of hepatotoxic compounds like indospicine. Consuming any part of these plants is extremely dangerous and should be avoided.
Potential Health Risks of Unregulated Indigo Consumption
Consumption of non-food-grade indigo can pose several serious risks due to variations in processing and potential toxic contaminants. The following are some of the dangers:
- Gastrointestinal Distress: Nausea, vomiting, diarrhea, and abdominal pain are common side effects associated with ingesting some forms of indigo, including both regulated food dye at high doses and unregulated herbal preparations.
- Hepatotoxicity (Liver Damage): Some species and unpurified extracts can cause liver damage. The presence of toxic amino acids like indospicine in certain Indigofera species makes them particularly dangerous.
- Pulmonary Hypertension: In rare but serious cases, long-term use of herbal indigo preparations for conditions like ulcerative colitis has been linked to pulmonary arterial hypertension, a severe condition affecting the heart and lungs.
- Allergic Reactions: As with any substance, allergic reactions can occur. Some individuals may experience skin irritation, and there have been reports of respiratory issues in people exposed to the powder.
- Contamination Risks: Unregulated herbal indigo, especially if purchased from unreliable sources, may be contaminated with other toxins or heavy metals, adding another layer of risk.
Comparison of Indigo Types
| Feature | Synthetic Indigo Carmine (E132/FD&C Blue No. 2) | Medicinal Plant Extracts (e.g., Indigo naturalis) | Wild & Toxic Indigo Species (e.g., I. spicata) |
|---|---|---|---|
| Source | Produced chemically in a lab | Derived from specific plants (B. cusia, P. tinctoria) | Various wild plants (Baptisia tinctoria, I. spicata) |
| Edibility | Approved food additive in controlled amounts | Used in Traditional Medicine, but safety concerns exist | Toxic; absolutely NOT for consumption |
| Regulation | Regulated by FDA, EFSA, etc. | Unregulated in most regions; efficacy and safety lack robust scientific support | Not intended for consumption; toxic compounds present |
| Key Concerns | Minor gastrointestinal issues, allergic reactions | Reversible liver damage, colitis, pulmonary hypertension | Severe toxicity, vomiting, diarrhea, liver damage |
The Verdict on Consuming Indigo
The safety of consuming indigo is not a straightforward yes or no answer. The crucial distinction lies in the type of indigo being considered. The only form generally accepted for human consumption is the synthetic food additive, indigo carmine (FD&C Blue No. 2), which is used in limited, regulated amounts in certain food products. Any attempt to consume other forms, including raw plant material, unprocessed herbal preparations, or wild species, carries significant and often serious health risks.
For those interested in the potential therapeutic benefits of plant-based indigo, it is vital to consult with a healthcare professional and use only expertly prepared and high-quality products under careful supervision. Given the documented risks of liver toxicity and other adverse effects, unsupervised use of herbal indigo is strongly discouraged. In summary, while a small, regulated amount of synthetic indigo dye is found in some foods, the raw plant material is not safe to consume and can be toxic.
For more information on the history and chemical properties of indigo carmine, read this detailed review of its uses and concerns: Indigo Carmine: Between Necessity and Concern - PMC.
