Fulvic Acid and Humic Acid are related compounds from decaying organic matter that have been employed to color some food and beverages black. The substances have been associated with natural medicine.

In the United States, products with fulvic/humic acids in them are labelled, "These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease." 

In Canada, there is a vodka [link] colored black with fulvic/humic acid. In the US, there are water and water additive drops colored black with these acids marketed as a sports recovery beverage. These products carry the FDA warning mentioned above. 

Definitions of Humic, Fulvic, Shilajit

"Humic substances are complex, weakly bound, superstructures of heterogenous, small organic compounds resulting from the decomposition of biological matter (i.e., plants and animals) and are ubiquitously present in soils and waters. Historically, humic acids have been defined as precipitates that form when basic extracts of humic matter are acidified while fulvic acids are those that remain in solution following this process. [source] 

"The origin of the idea that it might be healthful can be traced to the use of “shilajit” (rich in fulvic acids) in ayurvedic medicine—a holistic healing system developed in India." [source]

Safety and Danger of Fulvic/Humic Compounds

These compounds have been associated with treating everything from diabetes to pollen allergies, and the United States FDA has issued several warnings to products making unproved health claims for fulvic/humic acid products. For the purposes of their application as a coloring agents in food and beverages here we highlight some of the reported warnings and interactions:

• “Fulvic acid can increase oxidative stress and damage at higher doses,” says Dr. Bradley. “The actual pharmacological dosing is unknown in humans for safety.” [source]
• "If you’re pregnant, fulvic acid has not been proven safe to use; it also may worsen conditions like multiple sclerosis, lupus or rheumatoid arthritis, because of a possibly detrimental effect it can have on the immune system. Fulvic acid may also cause a condition called Kashin-Beck disease when consumed through drinking water in some people. In addition, fulvic acid can cause drug interactions. Some immune system therapy drugs that you do not want to take fulvic acid in tandem with include azathioprine, basiliximab, cyclosporine and prednisone, among others. Also, if you take anti-coagulants like Warfarin or aspirin, fulvic acid may cause these meds to work more slowly, putting you at an increased risk for blood clots. Thyroid medication may also be adversely affected in combination with fulvic acid." [source]
• "Fulvic acid products specifically containing shilajit products have actually caused lead poisoning due to high heavy metal concentrations. You just don’t know what you’re getting, and you don’t know how much is safe to take. Bottom line: never self-medicate with fulvic acid, or with any drug." [source]
• “Basically, it is a very potent compound, so I can tell you this is not something to be played with,” says Ghosh. “People have this idea that just because it’s a natural compound, it must be having a big therapeutic window. It is not like that.” [source]

Legal Status

It does not appear that humic/fulvic acid is approved in the United States as a food colorant. Much like activated charcoal, the black substance is used as a supplement instead of a food coloring, carrying the warning, "These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."

In the case of activated charcoal, some stores selling black-colored ice cream in the US were required to dispose of it, as it was not an approved coloring agent. Fulvic/Humic acid products are likely in this same legal status: a not-forbidden supplement as long as it is appropriately labelled, but not an approved food coloring. 

Recommendations for Alternatives

As with activated charcoal, if the goal is to turn cocktails black safely, some alternatives include:

• Squid or cuttlefish ink (note: not vegetarian)
• Black food coloring
• Ground black sesame seeds
• Black currant 

Further Reading

"A toxicological evaluation of a fulvic and humic acids preparation" Toxicology Reports [link]

"What’s the deal with all the black food and drink?" Toronto Star [link]

"What Is Fulvic Acid and Can the Supplement Help Treat Diabetes? We Investigated" Parade [link]