Medical Bulletin 12/December/2025

Your body relies on vitamin B12 for everything from energy production to nerve repair—but not all forms of this essential vitamin work the same way. A new comprehensive review in Cureus examines how natural and synthetic types of vitamin B12 differ in absorption, metabolism, and health effects, revealing why some people benefit more from certain forms than others.

Vitamin B12, also known as cobalamin, exists in three main forms—cyanocobalamin, methylcobalamin, and adenosylcobalamin. Found mainly in meat, eggs, and dairy, it plays a crucial role in red blood cell production, nerve function, and DNA synthesis. A deficiency can lead to megaloblastic anemia, neuropathy, and pregnancy complications. Although supplements can boost levels, the body’s ability to absorb and activate B12 depends on intricate biological steps.

When consumed through food, B12 is bound to protein and must first be freed by stomach enzymes. It then attaches to a protective carrier called haptocorrin, which shields it from stomach acid. In the small intestine, pancreatic enzymes break down this complex, allowing B12 to bind to intrinsic factor, a molecule secreted by stomach cells. This pair travels to the ileum, where specialized receptors absorb it into the bloodstream. Once absorbed, B12 binds to transcobalamin II to reach tissues, including the brain and bone marrow.

Inside the body, B12 acts as a cofactor in two key reactions: converting homocysteine into methionine, essential for DNA and cell repair, and supporting fat and protein metabolism through the enzyme methylmalonyl-CoA mutase, vital for healthy myelin in nerves. Without enough B12, cells divide abnormally, leading to enlarged red blood cells and neurological complications like numbness, memory loss, and balance problems.

The review highlights important differences between methylcobalamin (natural) and cyanocobalamin (synthetic) forms. While both raise blood levels, methylcobalamin appears more bioavailable and better for nerve health, partly because it doesn’t require the cyanide group to be detached before activation. It may also enhance serotonin production and support mood regulation.

Researchers recommend stronger B12 screening in vegans, vegetarians, older adults, and those with absorption disorders such as gastritis or Crohn’s disease. Ensuring adequate intake—about 2.4 µg per day for adults—from foods like salmon, beef liver, yogurt, or supplements is vital for long-term neurological and metabolic health.

This review reinforces one message: vitamin B12 is small but mighty, and choosing the right form—especially for those at risk—can make all the difference for your brain, blood, and body.

REFERENCE: Behringer, C. R., Kulkarni, A., Weinstein, A. (2025) Vitamin B12: A Comprehensive Review of Natural vs Synthetic Forms of Consumption and Supplementation. Cureus. doi:10.7759/cureus.96258, https://www.cureus.com/articles/403180-vitamin-b12-a-comprehensive-review-of-natural-vs-synthetic-forms-of-consumption-and-supplementation#!/

Omega-3 fats aren’t just good for your heart—they’re essential from birth to old age. A sweeping new review in Nutrition Research Reviews has brought together national and international data to outline how much omega-3 we really need, uncovering huge differences in recommendations across the world. These crucial long-chain fats—EPA, DHA, and DPA—support brain, eye, and heart health, strengthen immunity, and may even cut the risk of preterm birth, depression, and cognitive decline.

Omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) are most commonly found in fatty fish like salmon and sardines, but many people consume far less than their bodies need. The researchers examined 42 technical and dietary guideline documents (TSDs) from around the globe using records from the Food and Agriculture Organization’s global dietary repository and structured Google searches. Their goal was to map out how each country and organization defines adequate intake across life stages—from infants to older adults.

About 71% of these TSDs provided specific daily targets, while others included health messages or safety thresholds. Roughly half covered general healthy populations, while others addressed children (10%), adults (14%), pregnant women (12%), and older adults (5%). For infants, recommendations ranged widely—from 200 mg/day of DHA in Korea to 0.32% of all dietary fats from DHA for babies up to six months old. Children aged four to twelve were advised anywhere between 55 mg and 500 mg/day of DHA + EPA, while teenagers were recommended 70 mg to 500 mg/day depending on region.

For adults, 250 mg/day of DHA + EPA emerged as the most common benchmark, appearing in 18 national and international guidelines—including global authorities from Europe and the World Health Organization. During pregnancy, additional DHA is emphasized, often 100–200 mg/day above the adult recommendation, to support fetal brain and retinal development. Higher doses of up to 1 g/day were sometimes suggested for reducing preterm birth risk.

Interestingly, no clear upper limit was defined for infants, though most expert bodies capped adult intake between 2–5 g/day to avoid bleeding risks. Yet most populations worldwide still fall far short of even the minimum recommended levels.

The review concludes that achieving optimal omega-3 intake—through fish, fortified foods, or supplements—is vital for lifelong health, especially for populations with low seafood consumption. As the researchers note, consistent global guidelines and sustainable omega-3 sources will be key to closing this nutritional gap in the years ahead.

REFERENCE: Calder PC, Cawood AL, James C, Page F, Putnam S, Minihane AM (2025). An overview of national and international long chain omega-3 polyunsaturated fatty acid intake recommendations for healthy populations. Nutrition Research Reviews, 1–12. DOI: 10.1017/S0954422425100279, https://www.cambridge.org/core/journals/nutrition-research-reviews/article/an-overview-of-national-and-international-long-chain-omega3-polyunsaturated-fatty-acid-intake-recommendations-for-healthy-populations/2B7F6FD161EE90A7472B2B20909C4926