Urolithin A vs Vitamin B12: Energy Metabolism vs Energy Production

Reviewed by SOMA HEALTH's Medical Research Team

Both vitamin B12 and urolithin A get talked about in the language of energy, but they do very different jobs. B12 is a cofactor that helps convert the food you eat into usable fuel. Urolithin A supports the quality of the mitochondria that actually produce cellular energy from that fuel. This guide separates the two so you can see where each fits.

The one-line difference

Think of it as two stages of the same supply chain. Vitamin B12 works upstream, helping unlock energy from food. Urolithin A works on the machinery itself, supporting the mitochondria that carry out energy production and the cellular housekeeping that keeps those mitochondria in good shape. One is an essential micronutrient you must obtain to avoid deficiency; the other is a postbiotic studied for supporting mitochondrial quality as we age. They are not interchangeable, and they are not really competitors.

What vitamin B12 actually does

Vitamin B12 (cobalamin) is a water-soluble essential vitamin, which means your body cannot make it and you must get it from diet or supplements. It is found almost entirely in animal foods such as meat, fish, eggs, and dairy, which is why vegans, many older adults, and people with absorption issues are the groups most likely to fall short. Absorption also depends on a stomach protein called intrinsic factor, so it is not only about how much you eat.

Biochemically, B12 serves as a cofactor for two enzymes. One helps convert a byproduct of protein and fat breakdown (methylmalonyl-CoA) into a molecule that can enter the citric acid cycle, the pathway that feeds energy production. The other supports methylation and the recycling of homocysteine, which matters for DNA synthesis and healthy red blood cells. This is the real basis for B12 being described as helping turn food into energy: without enough of it, that conversion and healthy red-blood-cell formation stumble.

An important nuance about B12 and energy

Here is the honest part that supplement marketing often glosses over. B12 reliably relieves fatigue when that fatigue is caused by a deficiency. If your levels are already adequate, taking extra B12 has not been shown to hand you additional energy, because the vitamin is a facilitator, not a fuel. Persistent tiredness has many causes, so it is worth a conversation with your doctor and, if appropriate, a blood test rather than assuming a supplement is the answer. B12 supplementation is a treatment consideration for a diagnosed deficiency, which is a medical matter for your clinician, not something to self-diagnose.

What urolithin A does, and where the evidence stands

Urolithin A is not a vitamin. It is a gut postbiotic your body can make when specific bacteria break down ellagitannins from pomegranate, walnuts, and berries, though only some people carry the microbiome to convert it efficiently. Rather than helping extract energy from food, urolithin A is studied for supporting mitophagy, the process cells use to recycle worn-out mitochondria so healthier ones can do the work of energy production. Our explainer on mitophagy and the complete urolithin A guide go deeper on the mechanism.

Proven in humans

The first-in-human study (Andreux and colleagues, Nature Metabolism, 2019) found urolithin A safe and well tolerated up to 1,000 mg per day and produced a mitochondrial gene-expression signature. A 2022 trial in older adults (Liu, D'Amico and colleagues, JAMA Network Open) over about four months reported improved muscle endurance, and a 2022 trial in middle-aged adults (Singh and colleagues, Cell Reports Medicine) using 500 mg and 1,000 mg arms over four months found benefits in muscle strength and exercise performance.

Newer human research

A 2024 randomized trial in resistance-trained men (Journal of the International Society of Sports Nutrition) ran eight weeks, a 2025 Nature Aging randomized controlled trial of about 28 days reported support for immune-cell mitochondrial health in midlife adults, and further work in distance runners appeared in 2025. A 2024 systematic review in Ageing Research Reviews characterizes the overall picture as promising but still emerging.

Preclinical only

Foundational laboratory work, including Ryu and colleagues (Nature Medicine, 2016), demonstrated mitophagy, extended lifespan in C. elegans, and muscle effects in rodents, while later models explored joint and other endpoints. These are animal and cell findings and should be read as such, not as human-proven outcomes.