Vitamin B12: Benefits, Deficiencies, Food Sources

I haven’t bought meat or fish for over 10 years, and I don’t eat cheese either.

So I dug deeper into the question of vitamin B12: am I getting enough of it, since it’s particularly present in certain meats and fish?

What exactly is it used for? Where is it found? Can you really run out of it even if you eat a little animal products?

Here’s the fruit of my research and what I’ve learned to avoid vitamin B12 deficiency on a daily basis.

♻️ Last update: July 14, 2025.
👩‍⚖️ Declaration of financial interests: Amazon affiliate link. My complete declaration of financial interests is available in the legal notice section.
Written by Nelly Darbois, physiotherapist and scientific editor

A quick reminder of vitamin B12 (aka cobalamin) and its benefits

Vitamin B12 is an essential vitamin.

It helps your body to :

• produce red blood cells,
• protect your nerves, thanks to the sheath that surrounds them,
• make your brain work properly,
• make DNA.

Your body doesn’t produce them on its own. You must therefore consume it through food or supplements.

It is found mainly in animal products : meat, fish, eggs and dairy products. Some plant-based beverages and vegan products are enriched with B12, but this is not always sufficient.

If you’re deficient, it may take some time for the effects to appear. But a deficiency that is not taken seriously can have serious consequences (chronic fatigue, neurological disorders, etc.), even in children.

What are the signs of vitamin B12 deficiency?

B12 deficiency can cause :

• fatigue, even after a good night’s sleep,
• memory or concentration problems,
• dizziness,
• tingling in the hands or feet,
• a red, painful tongue,
• an unexplained drop in morale,
• paleness or yellowing of the skin.

The signs vary from person to person. And they may be discreet at first. So you may have a deficiency without knowing it.

A blood test is the quickest way to determine your vitamin B12 level. No need to fast.

This is a simple test, which can be prescribed by your GP. It can also be done directly in the laboratory, with or without a prescription (not reimbursed if without prescription, costing around €12).

Can B12 deficiency be compensated for by diet alone?

B12 deficiency can sometimes be compensated for by diet alone, but not always.

If you’re deficient but eat animal products regularly, you can sometimes slowly build up your levels with diet alone.

But it all depends on the severity of the deficiency and your ability to absorb B12 (some people, especially the elderly and those with digestive problems, absorb it poorly).

👉 In the case of a real deficiency, a supplement or injection is often necessary at the beginning, on medical prescription.

Only a blood test can tell you how far along you are.

Which foods are rich in vitamin B12?

This vitamin is produced… by bacteria!

Here are the main dietary sources of B12 (per standard serving):

Feed 🍽️	B12 (µg)	% of requirements / day ✅
Cooked beef liver (85 g) 🐄	70.7 µg	2940 % 🔥
Cooked clams (85 g) 🐚	17 µg	708 % 🔥
Cooked oysters (85 g) 🦪	14.9 µg	621 % 🔥
Enriched nutritional yeast (1/4 cup) ✨	8.3 to 24 µg	346 à 1000 % 🔥
Cooked salmon (85 g) 🐟	2.6 µg	108 % ✅
Canned tuna (85 g) 🐠	2.5 µg	104 % ✅
Cooked ground beef (85 g) 🍔	2.4 µg	100 % ✅
Milk 2% (250 ml) 🥛	1.3 µg	54 % ✅
Plain yogurt (170 g) 🥣	1.0 µg	43 % ✅
Enriched cereals (1 serving) 🥣	0.6 µg	25 % ✅
Cheddar cheese (40 g) 🧀	0.5 µg	19 %
Boiled egg (1 piece) 🥚	0.5 µg	19 %
Roast turkey (85 g) 🦃	0.3 µg	14 %
Tempeh (1/2 cup) 🌱	0.1 µg	3 %
Banana (1 piece) 🍌	0 µg	0 %
Wholemeal bread (1 slice) 🍞	0 µg	0 %
Strawberries (1/2 cup) 🍓	0 µg	0 %
Cooked kidney beans (1/2 cup) 🫘	0 µg	0 %
Spinach, cooked (1/2 cup) 🌿	0 µg	0 %

✅ Foods that cover 20% or more of daily B12 requirements are considered good sources of this nutrient.

➡️ Conclusion: if you don’t eat any animal products (including eggs and seafood), you should consume fortified products (such as yeast or cereals) or take a B12 supplement.

How much vitamin B12 should I take?

Here’s the minimum amount we think you should consume per day.

Age	Men 👨	Women 👩	Pregnancy 🤰	Breastfeeding 🤱
👶0 to 6 months*	0.4 µg	0.4 µg	–	–
👶7 to 12 months*	0.5 µg	0.5 µg	–	–
👶1 to 3 years	0.9 µg	0.9 µg	–	–
🧑4 to 8 years	1.2 µg	1.2 µg	–	–
🧑9 to 13 years	1.8 µg	1.8 µg	–	–
🧑14 to 18 years	2.4 µg	2.4 µg	2.6 µg	2.8 µg
19 years and over	2.4 µg	2.4 µg	2.6 µg	2.8 µg

These recommendations come from a group of experts in the United States: the Food and Nutrition Board (FNB), which is part of the National Academies of Sciences, Engineering and Medicine (see precise source at end of article).

There’s a broad consensus among health professionals (vegan and non-vegan alike) that B12 supplementation is essential for the optimal health of vegans. And the good news is that vegans who supplement often have better B12 status than meat eaters!

What can prevent the absorption of B12?

Some people do not produce an essential protein called intrinsic factor, which blocks absorption (this is rare).

Stomach surgery or illnesses such as Crohn’s or celiac disease can also impair assimilation.

Certain medications (such as omeprazole or metformin) or excessive alcohol consumption may reduce absorption.

To better absorb B12, chew supplements (if B12 tablets alone) andswallow multivitamins without chewing.

What can I do on a daily basis to prevent B12 deficiency?

During my 2 pregnancies and subsequent breastfeeding, I took a 25 µg B12 capsule every day, without exception (see on Amazon).

It was simple, well tolerated, and reassuring to know that our needs were well covered.

Outside these periods, I didn’t take any.

But lately, I’ve been re-evaluating the benefits of taking them more regularly. I need to motivate myself to quantify over a week the amount I consume with my current diet (I use the free FatSecret app for this, which is very handy).

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That’s all I wanted to say on the subject! Any questions or comments? See you in comments!