This is something that has peeked my curiosity. I am seeing way too many correlations with the human colon, our skin, fermentation and its metabolite melanoidins not to document this. Apparently our skin has the ability to ferment sugars.
Many topical self-tanners contain the compound dihydroxyacetone (DHA)[sugar]. Topical DHA[sugar] formulations come in lotions, gels, mousses, sprays, and wipes. DHA is a sugar molecule derived from plants that reacts chemically with the amino acids[proteins] in the stratum corneum[skin] to produce pigment when applied to the skin. This reaction is known as the “Maillard reaction,” and it does not require UVR[sun] to produce a pigment change. The resulting pigments are called melanoidins, which are similar in pigment to melanin.
Once DHA[sugar] is applied to the skin, it takes approximately two to four hours to begin the tanning[fermentation] process and can continue for 24 to 72 hours. DHA is resistant to normal water, soap, and sweat exposure. The tan will begin to fade gradually three to seven days after application result of normal skin exfoliation.
Melanoidins are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine (through the Maillard reaction) at high temperatures and low water activity. Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning, such as 1. Barley malts (Vienna and Munich), 2. Bread crust, 3. Bakery products and 4. Coffee. And humans too.
KEY -|- They are also present in the wastewater of sugar refineries, necessitating treatment in order to avoid contamination around the outflow of these refineries.
The polymers make the constituting dietary sugars and fats unavailable to the normal carbohydrate and fat metabolism. Dietary melanoidins themselves produce various effects in the organism: they decrease Phase I liver enzyme activity and promote glycation in vivo, which may contribute to diabetes, reduced vascular compliance and Alzheimer’s disease.
Some of the melanoidins are metabolized by the intestinal microflora.