Humic substances are complex organic substances of soil, which are formed in the process of humification. Humification involves natural chemical and microbial activity that transforms the dead remains of living things into humic substances.

It is the second greatest organic process on earth after photosynthesis and is responsible for fossil coal, oil deposits and others. Microorganisms utilize and break down organic substances and lead to accumulation of recalcitrant molecules. When microorganisms die, they are themselves broken down and added to the recalcitrant humic mass. The concurrent chemical-physical polymerization modifies humic substances in an unpredictable matter. In all, the genesis of humic substances can take hundreds or even thousands of years and leads to high variety, unique composition and extreme difficulties in characterization of these.

The growing interest of the modern society for environmental and biological welfare refreshed the attractiveness for implementation of humins. Gastroenterologists are often confronted with a wish of patients to be treated with “natural” products and asked for opinion on humic acids.

The study of the scientific literature reveals a large number of medical trials with dietary supplements of humic acids conducted all over the world. The reported effects include different, partially incoherent properties such as anti-inflammatory and immune-stimulatory as well as analgesic, antimicrobial, antiviral/anti-HIV activity, antioxidant and even stroke protective effects. The striking eclecticism of the findings and the lack of systematic studies make it difficult to build an unbiased opinion. Furthermore humic substances are distributed under a wide variety of trade names and descriptions in an unregulated market.

The colon is a central bio-fermenting organ degrading digestive leftovers. Since microbial activity is central in genesis and processing of humic acids, the innate human microbial communities should be the main object on which the effects of humic acids will be apparent.

Astonishingly, we found no data to this topic in the literature. In order to close this gap, we investigated the impact of orally applied Activomin® (Pharmawerk Weinboehla, Weinboehla, Germany) on concentrations and diversity of the human colonic microbiome. Activomin® is the only registered and standardized humic acids preparation in Germany.