Body odor (BO) is primarily caused by bacteria on the skin breaking down sweat. A persistent, unusual odor that hygiene practices fail to resolve often points toward internal metabolic processes and nutrition. The body’s ability to process compounds from food directly impacts the volatile chemicals released through the skin, breath, and urine. This suggests that nutritional deficiencies or metabolic conditions may cause a distinct, chronic smell originating from within the body.
Riboflavin Deficiency and the Metabolic Odor Connection
The vitamin deficiency most closely associated with a systemic body odor is a lack of Riboflavin (Vitamin B2). Riboflavin is a necessary component for the proper function of a liver enzyme involved in a specific metabolic pathway. While the chronic odor condition, Trimethylaminuria (TMAU), is typically genetic, a severe B2 deficiency can mimic or worsen its symptoms. TMAU is characterized by a strong, often fishy or rotten odor.
TMAU is linked to the liver’s inability to process the compound Trimethylamine (TMA), which is a product of gut bacteria. Riboflavin is a precursor to a cofactor that helps the Flavin-containing monooxygenase 3 (FMO3) enzyme function correctly. Without enough B2, the FMO3 enzyme becomes less efficient at neutralizing TMA. A nutritional deficiency in riboflavin can thus impair the metabolic function needed to prevent the odor from manifesting.
In patients with a known FMO3 gene variation, administering riboflavin supplements has been shown to reduce the excretion of the foul-smelling chemical. This effect highlights the vitamin’s role in supporting the enzyme’s activity, even in individuals with a genetic predisposition to the disorder.
The Chemical Process Behind Body Odor Formation
The specific, strong odor associated with metabolic issues like TMAU is caused by the chemical Trimethylamine (TMA). This volatile organic compound is produced in the gut when intestinal bacteria break down dietary substances, such as choline and carnitine. These precursors are abundant in foods like eggs, meats, and legumes. Once formed, TMA is absorbed into the bloodstream and travels to the liver for detoxification.
In a healthy system, the FMO3 enzyme, which is primarily found in the liver, performs a chemical reaction called N-oxidation. This process converts the fishy-smelling TMA into an odorless compound known as Trimethylamine N-oxide (TMAO). The resulting TMAO is easily excreted by the kidneys through urine without causing any noticeable scent. This conversion is the body’s primary defense against the odorous chemical.
When the FMO3 enzyme is impaired, due to a genetic variant or lack of necessary cofactors derived from Riboflavin, this conversion fails. Unprocessed TMA accumulates in the bloodstream and must find alternative routes for elimination. The excess TMA is released through all bodily secretions, including sweat, breath, saliva, and urine, causing the distinct, persistent, and unpleasant odor.
Other Dietary Influences on Body Odor
Beyond the metabolic disorder linked to riboflavin, other dietary choices can influence a person’s scent. Foods containing high levels of sulfur compounds, such as garlic, onions, and cruciferous vegetables like broccoli and cabbage, contribute to altered body odor. The breakdown of these compounds releases volatile sulfur-containing gases that are absorbed into the bloodstream and released through the lungs and skin. These odors differ from the fishy smell of TMAU and relate to the concentration of sulfur gases.
High-fat, low-carbohydrate plans like the ketogenic diet can lead to a distinctive scent often described as fruity or similar to nail polish remover. This “keto body odor” results from the body entering ketosis, where it burns fat for fuel and produces ketone bodies. One of these ketones, acetone, is volatile and is excreted through the breath and sweat glands. This scent change is a sign of metabolic shift and usually subsides as the body adapts.
Diets extremely high in protein can also result in a pungent, ammonia-like odor. When the body breaks down excessive protein, it must process more nitrogen, which is converted to ammonia. If the liver and kidneys are overwhelmed, this surplus ammonia is released through sweat, contributing to a strong, sharp smell. These diet-related odors represent a functional overload or metabolic byproduct rather than a true vitamin deficiency or genetic enzyme failure.