Vitamin B12

Becky
Jul 23
4 min read

Updated: Aug 31

Vitamin B12 – The Energy and Nerve Protector

Vitamin B12 (cobalamin) is an essential water-soluble vitamin that supports energy production, red blood cell formation, and the nervous system.

It is also vital for DNA synthesis and mental clarity.

Since the body cannot produce B12, it must be obtained through food or supplements.

Up to 39% of the US population could have low B12 levels.

Why Vitamin B12 Is Important

Boosts Energy – Helps convert food into energy at a cellular level.

Supports Nerve Health – Maintains the protective myelin sheath around nerves.

Prevents Anaemia – A deficiency can lead to megaloblastic anaemia, causing fatigue and weakness.

Brain Function – Linked to memory, focus, and mood regulation.

Homocysteine Balance – Works in conjunction with folate and vitamin B6 to maintain healthy homocysteine levels, reducing the risk of heart disease, stroke, and dementia.

Active Forms of B12 that our cells use:

Methylcobalamin: Used in homocysteine metabolism (works with folate).

Adenosylcobalamin: Required for mitochondrial energy production (fatty acid/amino acid breakdown).

Vitamin B12 needs to be activated by Riboflavin B2 (in the form of FMN/FAD).

B2 activation into FMN & FAD requires three key minerals: Iodine, Selenium, and Molybdenum.

Any deficiencies in these minerals: → B2 remains inactive → B12 can't function.

For more information, see my blog on vitamin B2.

Recommended Daily Intake (RDI)

• Adults (men & women): 2.4 μg/day

• Pregnancy: 2.6 μg/day

• Breastfeeding: 2.8 μg/day

(Older adults and vegans are at higher risk of deficiency and may need supplements.)

Signs of Vitamin B12 Deficiency

Fatigue or low energy

Numbness, tingling, or "pins and needles"

Brain fog or poor memory

Pale skin or shortness of breath

Mood changes, anxiety, or depression

Smooth, sore tongue or mouth ulcers

Top Food Sources of Vitamin B12

Chicken liver: 1 liver (50 g) = 8.3 μg

Beef: 100 g = 5.0 μg

Sardines: 100 g = 8.9 μg

Salmon: 100 g = 4.2 μg

Eggs: 2 eggs = 1.1 μg

Greek yogurt (plain): 200 g = 1.4 μg

Fortified nutritional yeast: 1 tbsp = 2.4 μg

Fortified plant milks: ~1 μg per cup (check label)

Why Keeping a 5-Day Food Diary is So Helpful

(Especially with a Free App Like Cronometer)

If you've ever wondered whether you're getting enough vitamins and minerals from your diet, keeping a food diary for 5 days can be a real eye-opener. Using a free app like Cronometer makes the process simple and surprisingly insightful.

Cronometer doesn't just track calories — it gives you a full nutritional breakdown of the food you eat each day. You'll quickly see where your diet is strong and where you might be missing out on important nutrients like B12, magnesium, or iron.

One of the best things about using an app like this is that you can experiment. Try swapping in nutrient-dense foods — such as chicken liver, beets, or romaine lettuce — and see how even small changes can dramatically improve your nutrient intake.

If you're using my one-day meal plans for specific vitamins and minerals, keep in mind: they're just examples to show what's possible. Cronometer helps you take it a step further by tailoring things to your own diet, preferences, and needs.

Tracking for just 5 days can give you a clearer picture of how your current eating habits support your health — and where a few smart tweaks can make all the difference.

Meal Plan to Meet B12 Needs (2.4 μg)

Breakfast: = 2.1 μg

Scrambled eggs (2 eggs – 1.1 μg)

A cup of fortified oat milk in coffee or porridge (1 μg).

Lunch: = 4.4 μg

Sardine salad on wholegrain toast (50 g sardines – 4.4 μg).

Snack: = 1.4 μg

Greek yoghurt (200 g – 1.4 μg).

Dinner: = 8.3 μg

Grilled chicken liver (1 liver, 50 g – 8.3 μg) with sautéed greens.

Total: ~16.2 μg (well above the RDI).

Vitamin B12 and Vegan Diets

Vitamin B12 is found almost exclusively in animal products. There is no bioactive B12 in plants unless they have been fortified with it.

Note: Spirulina contains analogues that block B12 absorption.

Vegans must rely on fortified foods or take a reliable B12 supplement.

Vitamin B12 Supplements – Do You Need Them?

The most common cause of B12 deficiency is poor absorption, which can result from conditions such as irritable bowel disease, celiac disease, AIDS, or bacterial overgrowth in the small intestine.

Elderly individuals: Atrophic gastritis can lead to a 10–30% reduction in the ability to absorb food-bound vitamin B12, necessitating the use of fortified foods or supplements, as vitamin B12 absorption declines with age.

Vegan Diets and Infants of Vegan Mothers: Risk of Deficiency.

Pernicious anaemia (autoimmune destruction of IF-producing cells) makes absorbing oral B12 impossible.

The only B12 I use is Greg Russell-Jones’ B12 topical skin oils; the version I like is the B12 Ice version, which helps with inflammation, or the methyl/adenosyl B12 available here.

B12 Oils

This video is a must-watch for anyone looking to learn about vitamin B12.

It provides comprehensive information on how oral B12 is absorbed, the importance of testing B12 levels, and how high-dose oral supplements can exacerbate B12 deficiency.

It also highlights the importance of activating B12 through the active form of vitamin B2.

Interactions

PPIs/H2 blockers (reduce stomach acid impacting B12 absorption.

Metformin: Reduces B12 absorption (monitor levels).

Nitrous Oxide: Inactivates B12 (acute deficiency risk in surgery/drug abuse).

Paclitaxel, an anticancer drug that leads to irreversible cell injury, B12 was protective against the known free radical damage.

Hydrochlorothiazide - B12 reduced toxicity, a diuretic drug used to treat high blood pressure and fluid-related swelling.

Some people like Elliot are sensitive to B12 supplements and require a lot of high-potassium food to cope with the increased adrenaline it produces (see the video above).