Body odor, or BO, is a natural human phenomenon, but when the scent changes unexpectedly, supplements are often the cause. The smell we perceive as body odor is not actually sweat itself, but the byproducts of skin bacteria breaking down sweat and other secretions. Supplements can introduce high concentrations of specific compounds into the body that, when processed, result in volatile, odorous molecules. These molecules are then excreted through various pathways, leading to temporary or persistent changes in a person’s natural scent.
How Supplements Change Metabolic Odor
The process begins in the digestive system, where gut microbiota interact with supplement compounds before they are absorbed into the bloodstream. The body’s primary detoxification organs, the liver and kidneys, work to metabolize and neutralize these chemical substances. When the intake of certain compounds exceeds the body’s capacity to process them efficiently, the excess is diverted for excretion through alternative routes.
The skin and lungs become major pathways for eliminating these metabolic byproducts, leading to distinct odors in sweat and breath. For instance, sulfur-containing compounds are highly volatile and easily pass through the bloodstream to the lungs, causing odorous breath, and to the eccrine sweat glands, resulting in a noticeable skin scent. Similarly, the breakdown of certain nutrients by gut bacteria can produce compounds that circulate in the blood until they are released through the pores.
A key metabolic pathway involves intestinal microbes converting compounds like choline into trimethylamine (TMA). Normally, the liver enzyme flavin-containing monooxygenase 3 (FMO3) converts the fishy-smelling TMA into its odorless form, trimethylamine N-oxide (TMAO). However, a high load of TMA precursors can overwhelm FMO3, causing TMA to accumulate and be released through sweat, urine, and breath. This mechanism explains the distinct fishy odor associated with certain supplements, especially in individuals with reduced FMO3 enzyme function.
Key Supplements Linked to Odor Changes
Several common supplements contain compounds that produce distinct metabolic odors when taken in high doses. Supplements containing high levels of choline, such as lecithin and alpha-GPC, are often implicated in causing a fishy body odor. This occurs because gut microbiota metabolize the excess choline into trimethylamine (TMA). L-carnitine supplements can cause the same fishy scent, as this compound is also a precursor to TMA production.
High-dose B vitamins, particularly Thiamine (Vitamin B1), can lead to a “yeasty” or strong, medicinal scent. Thiamine is an organosulfur compound, and its metabolism releases volatile, sulfur-containing byproducts that are easily excreted in sweat and urine. When B-complex formulas contain choline, they can also contribute to the fishy odor.
Fish oil, rich in Omega-3 fatty acids, can cause a fishy smell, often manifesting as “fish burps” or a faint odor on the skin. This effect is related to the quality and freshness of the oil. Polyunsaturated fats are highly susceptible to oxidation (rancidity) upon exposure to light, heat, or air. Consuming rancid or oxidized fish oil, common in many commercial products, leads to unpleasant tastes, smells, and the excretion of oxidized metabolites.
Herbal supplements like garlic and fenugreek are notorious for causing a persistent, pungent body odor and breath. Garlic contains alliin, which converts into allicin when ingested, becoming the precursor to various volatile organic sulfur compounds (VOSCs). These VOSCs, such as diallyl disulfide and allyl methyl sulfide, are absorbed into the bloodstream and slowly released through the lungs and skin pores, leading to a long-lasting scent. Fenugreek contains sotolone, a compound also found in maple syrup, which can give sweat and urine a sweet, curry-like smell.
Strategies for Managing Odor Side Effects
For people experiencing supplement-related odor, the first intervention is dosage adjustment. Splitting the daily dose of a supplement, such as choline or L-carnitine, into smaller amounts taken throughout the day prevents the metabolic system from becoming overwhelmed. This allows the liver more time to process the compounds into non-odorous forms, reducing the amount of volatile chemicals released.
Improving hydration aids the kidneys in flushing out water-soluble metabolic waste. Pay attention to the quality of fish oil supplements; fresh fish oil should not taste or smell strongly fishy. Switching to an enteric-coated fish oil capsule can prevent the oil from being digested until it reaches the small intestine, significantly reducing fish burps and resulting odor.
In cases of persistent fishy odor, particularly with choline or carnitine, supplementing with Riboflavin (Vitamin B2) can help. Riboflavin is a cofactor that increases the activity of the FMO3 enzyme, assisting the body in converting odorous trimethylamine into odorless trimethylamine N-oxide. If simple adjustments fail to resolve the issue, or if the odor is severe and accompanied by other unusual symptoms, consult a healthcare provider.