Evolution Toward a Useless Gut: Physiological Consequences of Unnecessary Supplementation: A Narrative Review

This narrative review aims to critically examine the physiological, microbiological, and public health consequences of chronic dietary supplementation in healthy individuals without clinical indications. The review explores the hypothesis that unnecessary supplementation may impair intestinal function and nutrient homeostasis through adaptive mechanisms.

A narrative review was conducted using indexed scientific literature published during 2009-2024. Studies in both humans and animal models were included. The review examined the effects of prolonged micronutrient and macronutrient supplementation on intestinal transporters, digestive enzyme activity, gut microbiota composition, and evolutionary physiology.

Chronic supplementation was found to induce the physiological downregulation of intestinal transporters (eg, sodium-dependent vitamin C transporter 1 [SVCT1]; transient receptor potential vanilloid 6 [TRPV6], a protein that acts as a calcium channel in cell membranes; and ferroportin), reduce digestive enzyme secretion, and alter gut microbiota composition. The effects included a loss of microbial diversity and short-chain fatty acid (SCFA) production and were associated with impaired absorption, reduced digestive efficiency, and the potential for long-term intestinal dependence on external nutrient input. Furthermore, evidence of pharmacological interactions and adverse effects such as hepatotoxicity and nephrotoxicity has been documented.

In the absence of a qualified health care professional, the chronic use of nutritional supplements may trigger intestinal adaptations that compromise natural digestive and absorptive functions. This phenomenon has physiological, evolutionary and public health implications. Health policies and clinical practice should therefore promote the evidence-based use of supplements and reinforce the importance of dietary diversity.