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Vitamin B12: Vegetarian Nutrient of Concern #1

Jennifer Hanes MS, RDN, LD

As we discussed before, a vegetarian diet can be very healthy when it is well-planned. However, if you aren’t ensuring you meet all of your nutritional needs, it is possible to have certain nutritional deficiencies that can have a bad effect on your health.

This post is the first in a series on the nutrients that were briefly discussed in my post: Are You An Unhealthy Vegetarian?

Understanding Vitamin B12

B12, otherwise known as cobalamin, serves many functions in our body.

It is commonly touted as a nutrient to give you more energy, which can be true. But only if you are deficient.

This vitamin is found only in animal products, so vegetarians, particularly vegans, need to pay attention to their intake. Vegans must seek out supplementation or fortified foods, or they may experience irreversible neurological problems.

Frustratingly, vitamin B12 deficiency is not always caused by an inadequate intake. Because this nutrient can be hard to absorb, certain GI conditions, advanced age, medication interactions, and more can lead to deficiency despite getting enough in your diet.

Functions of Vitamin B12

Vitamin B12 has a variety of functions in the body.

Vitamin B12 is directly responsible for red blood cell formation, neurological function, and DNA synthesis.

It is also involved in approximately 100 different metabolic processes, including the function of our genetic material (DNA and RNA), various proteins, hormones, and fats. 

Vitamin B12 is also a component in the metabolic breakdown of proteins, fats, and the formation of hemoglobin which is the oxygen-carrying component of your red blood cells.

Additionally, cobalamin is also responsible for the metabolism of another B vitamin, folate. If B12 and folate are deficient, homocysteine can build up in the bloodstream, increasing your likelihood of developing heart disease.

B12 deficiency has been linked to an increased risk of breast cancer and neural tube deficits in babies.

Finally, it has been suggested that B12 deficiency contributes to dementia symptoms in older adults due to its role in the protection of various neurons.

Cheese plate, a minor source of B12 in the vegetarian diet.

Recommended intake of Vitamin B12

After the age of 14, the recommended intake of vitamin B12 is 2.4 mcg per day.

Your B12 needs increase to 2.6 mcg in pregnancy and 2.8 mcg when breastfeeding.

Milk, which has plenty of vitamin B12


Vitamin B12 is only found in animal sources. Oysters and liver actually contain over 100% of your daily needs in a 3oz serving!

Fish and beef are the top sources of vitamin B12 in most Americans.

A cup of milk contains 1.2 mcg, and 8 oz of yogurt has 1.1 mcg.

Ham, eggs, chicken, and cheese also contain some vitamin B12.

Finally, fortified foods can be good sources, such as nutritional yeast and fortified breakfast cereals.

Non-food sources of vitamin B12 include sublingual drops, dissolvable tablets, nasal sprays, and injections.

It has been suggested that all individuals over the age of 51 should ensure that they get at least 2.4 mcg from supplements and/or fortified foods.

This is because the absorption of B12 tends to be better from supplements (by up to 50%) when compared to natural food sources.

Eggs in heart shape, on toast.
Eggs contain some B12 as well

Symptoms of deficiency

Because your liver can store up to 6 months of your B12 needs, inadequacy in your diet may be slow to reveal itself.

The major symptoms of B12 deficiency are anemia (different from iron deficiency anemia), fatigue, weakness, constipation, loss of appetite, and weight loss. 

If deficiency persists, you may experience neurological symptoms such as numbness or tingling of the hands and feet.

Less common symptoms can include difficulty maintaining balance, depression, confusion, dementia, poor memory, and soreness of the mouth and tongue.

Causes of secondary deficiency

When talking about nutrients, primary deficiency occurs when the diet does not include enough of that particular nutrient. Secondary deficiency occurs due to poor absorption, increased elimination, or increased needs for that nutrient.

In the case of vitamin B12, secondary deficiencies occur when people have pernicious anemia or gastrointestinal disorders (such as Celiac or Crohn’s diseases).

Those who have had surgery on their GI tract may be missing key components in the B12 absorption process.

Sometimes, medications can interfere with the absorption of B12. Heartburn medications are the most common culprit for this. 

Medications used to treat gout, diabetes (Metformin), and high cholesterol can also inhibit the absorption of vitamin B12.

Finally, substance abuse, particularly alcohol, can increase your body’s use of B12 while simultaneously reducing food intake and the amount of B12 that is absorbed.

Treatments for deficiency

Treatment for B12 deficiency involves injections. Many times, taking high doses of oral supplements is not effective. This is because the absorption of vitamin B12 involves many steps, and failure of any of those steps means you cannot absorb the nutrient. 

Injections cause the B12 to go directly into your bloodstream, bypassing any potential points of poor absorption.

Yogurt with berries. Greek yogurt is an excellent source of B12 and protein.

Symptoms of toxicity

There are no documented reports of toxicity from vitamin B12, regardless of if the high amounts come from food or supplement sources, possibly due to the low absorption rates of the nutrient.

Assessing B12 status

The first time vitamin B12 deficiency is detected is usually due to symptoms the person is experiencing. Fatigue and brain fog, in the absence of thyroid problems, is a good example.   

Annual lab work usually doesn’t include testing for vitamin B12 levels. However, the basic workup could potentially show a low number of red blood cells (anemia) that are larger than normal.

If symptoms, lab work, and intake analysis indicate vitamin B12 deficiency, there are 2 labs that can assess your status.

Serum vitamin B12 is a simple blood test that is usually the first option. If you’ve already had your blood drawn, it is likely that your doctor can simply call the lab and have them test rather than getting more.   

Most labs consider levels over 200-250 ug to be normal. However, optimal levels are over 500 ug, and many people will feel deficient if their serum B12 is <500 ug.

Another test, Methylmalonic Acid (MMA), is a more sensitive test for B12 status. In reality, elevated serum levels of MMA can indicate vitamin B12 deficiency BEFORE low levels of B12 show up on lab work. 

However, kidney disease can also cause high MMA levels.

Elevated homocysteine levels can also be due to vitamin B12 deficiency. However, there are a lot of other causes for high homocysteine levels. This is not a test that holds a lot of value for most people.

Not everyone needs to have their B12 levels evaluated regularly. 

However, I strongly believe that anyone struggling with substance abuse, anyone with GI disorders, vegans, and individuals who take medications that interfere with vitamin B12 absorption should have their B12 and/or MMA levels checked at least once per year.

Should I take a Vitamin B12 supplement?

For a large proportion of people, supplementation is not necessary. However, if you are taking a medication that inhibits absorption or if you have GI problems or have had GI surgery, you should discuss the need for supplementation with your doctor.

If you are vegan or vegetarian with low dairy intake, you should also take a supplement or make sure to include vitamin B12-fortified foods.

What supplementation won’t do

If your diet includes adequate B12 and you don’t have any problems that inhibit absorption, supplementing with B12 probably won’t help you.

Despite common claims, B vitamins do not give you more energy, though deficiency reduces your ability to convert your food into useful energy.

Any concern for the omnivores?

For the omnivores in your family, B12 is not generally a nutrient of concern, even if they eat vegetarian only at home. Meals that include meat otherwise will cover them! 

Bottom Line

For vegans, vitamin B12 is a nutrient that should be supplemented daily, as they have no natural source in their food supply. Vegetarians can eat adequate amounts throughout their diet and are less prone to B12 deficiency than their vegan counterparts.

However, depending on how much dairy and eggs they consume, primary deficiency is possible. Their risk of deficiency increases if they are taking certain medications or have malabsorption difficulties due to gastrointestinal disorders.

Our omnivorous buddies are probably okay, unless they have the conditions listed above for secondary deficiency of vitamin B12.

infographic summarizing the functions, recommended intake, sources, symptoms of deficiency and causes of secondary deficiency of vitamin B12
Is it okay to take Vitamin B12 daily?

For the most part, yes. The risk of vitamin B12 is very low. If you don’t need the B12, your body will make sure it’s liver storage is full, then you’ll pee it out.
That being said, there could potentially be financial harm from taking a supplement that isn’t necessary. 
Vegans should be taking a supplement daily.

What happens when your Vitamin B12 is low?

Essentially, your metabolism slows down. You’ll experience fatigue and brain fog, or confusion. If not treated, low B12 can lead to anemia and neurological damage.

How does vitamin B12 deficiency occur?

Primary B12 deficiency occurs when you do not ingest enough vitamin B12, either through food or supplements. This is most likely when on a vegan diet, but can occur in some vegetarians as well.
Secondary B12 deficiency occurs when you take in enough vitamin B12, but your body does not absorb it as it should. This can occur in all gut diseases, alcohol abuse, and because of some medications.

Should Vitamin B12 be taken in the morning or at night?

In general, it doesn’t matter. Take it when you’ll remember it.
However, sometimes, if you’ve been deficient, you may feel a “boost” of energy as you restore your vitamin B12 stores. Some people find that this can interfere with sleep and should take the supplement in the morning.

Should Vitamin B12 be taken with or without food?

This won’t matter. Vitamin B12 is a water-soluble vitamin, meaning it does not need fat to be absorbed. However, the presence of fat does not reduce the absorption of B12.
The best time to take a vitamin B12 supplement is when you will consistently remember it.

Should Vitamin B12 be refrigerated?

Most b12 supplements do not require refrigeration, but will also not be harmed by it. 
The best bet is to follow the storage instructions on the label of your favorite brand.

Jenn in a grey and white half sleeved shirt in front of a beige wall and a abstract city painting

Jennifer Hanes MS, RDN, LD is a registered dietitian, mom, wife, and vegetarian in North Texas. She has dedicated Dietitian Jenn to be a source of information, ideas, and inspiration for people like her, vegetarians that live with people with different dietary beliefs and/or needs in a multivore household.

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