Fish Food! Your Vegan Source of B12 is in Algae

by Lauren Armstrong — Registered Dietician, BSc Dietetics
August 31, 2020

You usually can’t get away with being a vegan without someone expressing concern regarding how much vitamin B12 you get. It’s a valid topic to discuss since vitamin B12 is almost exclusively animal-based and only found in tiny traces in plant-based foods.

Vitamin B12 is essential to life as it plays a role in creating new DNA for new cell growth. If you’re not getting new DNA, then there will be no new cells. That includes our blood cells, which are vital to survival.

If B12 is exclusive to animal products, how can vegans ensure they are meeting their needs? We’re diving underwater to answer that.

Role of vitamin B12 in a vegan diet

We discussed how vitamin B12 creates new DNA, but it has several other vital functions. It keeps your nerves healthy and prevents a condition called megaloblastic anemia, which produces symptoms of feeling weak and tired.

Some other symptoms that may occur If your intake is limited and you’re becoming deficient includes:

Another B vitamin called folic acid can mask a B12 deficiency by correcting megaloblastic anemia, one of the most significant deficiency indicators.

Since B12 is a big component of keeping your nervous system healthy, it will still create damage since folic acid cannot correct that. For this reason, keeping folic acid intake to no more than 1,000 mcg per day is ideal.

What are the symptoms of B12 deficiency?

You never know when symptoms may show up once you become B12 deficient. Some show their face quickly, but sometimes they appear gradually and become more intense with time.

Since there are so many different symptoms from a vitamin B12 deficiency, it can be easily confused with another condition.

Symptoms that may occur If your B12 intake is limited and you’re becoming deficient includes:

Getting B12 deficiency detected early is crucial. When untreated, it can result in severe neurologic conditions and blood diseases.

If you’re noticing these symptoms, ask your doctor to get your blood levels checked. This will be able to confirm if what you’re experiencing is a B12 deficiency.

So, if I’m vegan, how hard is it to meet my Daily Value?

We’ll be honest; it can be pretty tough to get enough vitamin B12 via diet when you’re vegan.

Most B12 sources are animal products, with very minimal being vegan-friendly. Even if you were to stock up on vegan B12 foods, some factors could affect your body from absorbing it entirely. Even how the product is shipped or stocked could affect the overall balance of B12.

There are back and forth beliefs you can get in enough B12 if you eat the right plant foods or even choosing unwashed organic produce, but there aren’t enough scientific studies to back those up.

That’s why vegans should choose a B12 supplement to take regularly. Especially if you’re over the age of 51 because your ability to absorb B12 decreases with age. This ensures that your daily value is being reached consistently.

Food sources of vitamin B12

This is where it gets tricky! The majority of foods containing vitamin B12 come from animal products, with beef liver, clams, fish, and other dairy products containing high amounts.

Some plant-based foods can contain lower amounts of B12, these include:

Nori, spirulina, and chlorella are all types of algae that contain traces of vitamin B12. This is due to a bacteria that resides on their surfaces. Unfortunately, it’s hard to measure how much B12 these algae contain since the factor can depend on regions and the physiological state of the algae, according to a 2017 article.

Your body also uses a protein called intrinsic factor, which is necessary for your body to absorb vitamin B12. It’s found in cells that line your stomach and attach to B12 for it to be absorbed by your intestines. The kicker is, only 56% of a one mcg dose of vitamin B12 is absorbed.

For these reasons, it’s best not to depend on algae for your B12 needs ultimately. You likely need to eat large portions to even make a dent in your recommended intake of vitamin B12.

Here are the Recommended Dietary Allowances (RDAs) in micrograms (mg) for vitamin B12.

Age Male Female Pregnancy Lactation
Birth to 6 months 0.4 mcg 0.4 mcg    
7 to 12 months 0.5 mcg 0.5 mcg    
1 to 3 years 0.9 mcg 0.9 mcg    
4 to 8 years 1.2 mcg 1.2 mcg    
9 to 13 years 1.8 mcg 1.8 mcg    
14+ years 2.4 mcg 2.4 mcg 2.6 mcg 2.8 mcg

Is a vitamin B-12 supplement necessary in a vegan diet?

As a vegan, your best to ensure the proper intake of B12 is by committing to a daily supplement.

A 2019 study oversaw 151 healthy vegans and 85 healthy non-vegans. The purpose was to find whether there were nutritional deficiencies among vegans and if supplement use is beneficial. The results found that vegans have much lower vitamin B12 compared to non-vegans, except when they supplement vitamin B12.

When it comes to B12 supplementation, vegans who are taking a supplement irregularly have a 4% higher risk of deficiency, and non-supplement vegans have about a 22% higher risk of deficiency than vegans who are supplementing on the reg.


Algae is why fish contain B12 (it’s their food!), but it’s not enough to keep our B12 stores up to par. This doesn’t mean that you can’t eat algae if you enjoy it, but it’s essential to add a supplement to your day.

Have a chat with your doctor first, but it’s almost certain they will want you to be supplementing B12 if you are following a strict and long-term vegan diet.