Vitamin B12 is one of the most essential nutrients for human health, yet many people don’t get enough — particularly those following plant-based diets. This nutrient plays a critical role in energy production, nerve function, DNA synthesis, and the formation of healthy red blood cells. Without enough B12, fatigue, low mood, neurological symptoms, and even anemia can develop over time.
Humans cannot produce B12 on their own. Unlike some vitamins that can be made in the body from precursors or found widely in plant foods, B12 is naturally synthesised only by certain bacteria. Animals obtain B12 by consuming these bacteria, often indirectly through soil, water, or other animals, and humans then receive B12 when eating animal-derived foods such as meat, fish, eggs, and dairy.
Why Plant Sources Aren’t Enough
Some plant foods are sometimes cited as containing B12, such as algae (spirulina, nori, chlorella), fermented foods (tempeh, miso, kimchi), or certain mushrooms and seaweed. While these foods may contain traces of B12 or B12-like compounds, most of these are inactive analogues that the human body cannot use. The amounts in these foods are also highly variable and unpredictable.
This means that relying on unfortified plant foods alone is not sufficient to meet daily B12 requirements. The only reliable plant-based sources of B12 are fortified foods such as plant milks, breakfast cereals, or nutritional yeast, or supplements that provide a consistent, usable form of the vitamin.
For vegetarians, vegans, older adults, and people with absorption issues (such as those with gastrointestinal conditions), supplementation or fortified foods are essential to prevent deficiency.
Signs You May Need More B12
B12 deficiency can take years to develop because the body stores it in the liver. Symptoms can be subtle initially but may include:
- Fatigue or low energy
- Pale or jaundiced skin
- Numbness or tingling in hands and feet
- Mood changes, irritability, or low motivation
- Cognitive difficulties or brain fog
- Glossy or sore tongue
Routine blood tests can check B12 levels, especially if you are at risk due to diet or medical conditions.
How Much B12 Do You Need?
The recommended dietary intake (RDI) for adults is around 2.4 micrograms per day, increasing slightly during pregnancy or breastfeeding. While small amounts are sufficient, the body relies on consistent intake because it cannot make B12 independently. For those at risk of low absorption, higher doses via supplements may be recommended.
Practical Ways to Meet B12 Needs
For omnivores, animal-based foods remain the most reliable sources:
- Lean meats such as beef, chicken, or pork
- Fish and seafood
- Eggs and dairy products
For vegetarians and vegans:
- Fortified plant milks, breakfast cereals, or nutritional yeast
- B12 supplements (oral tablets or sublingual forms)
- Regular monitoring of blood levels to ensure adequacy
It’s important to note that simply eating more plant foods alone will not provide enough usable B12. Fortification and supplementation are the safest ways to prevent deficiency.
Tips for Daily B12 Support
- Include a fortified food or supplement daily
- Pair supplements with meals that contain some fat for better absorption
- For older adults, check with a healthcare provider about the best supplement form
- If you follow a vegan or vegetarian diet long-term, consider a B12-only supplement rather than relying on multivitamins that may have insufficient amounts
Take Home Message
Vitamin B12 is vital for energy, nerves, blood health, and brain function. Humans cannot make it, and plant foods alone do not provide sufficient active B12. Ensuring reliable sources — either through fortified foods or supplements — is essential for maintaining health, particularly for vegetarians, vegans, older adults, and those with absorption issues.
If you would like personalised guidance on meeting your B12 needs or managing a plant-based diet without compromising your health, Feed Your Future Dietetics can help. With over 10 years of experience and voted one of Canberra’s best dietitians in 2025, Feed Your Future Dietetics provides individualised Telehealth and Zoom consultations to support clients all around Australia.
