All you need to know about vitamin B12
by Simone do Carmo
in Blogs

A recent study published in the Journal of Affective Disorders shows that vegetarian diets are associated with depressive symptoms among men. The authors speculate that this association could be explained by nutritional deficiencies.

Indeed, not being properly educated about plant-based eating can lead to many nutritional deficiencies, including iron and vitamin B12. Because it is only found in animal foods, vitamin B12 deficiencies can be a major concern for restrictive vegetarians.

What is vitamin B12 and why is it important?

Vitamin B12 is a water-soluble vitamin, meaning that it’s easily absorbed in the body and any excess amounts are excreted through our urine. Our body can’t make vitamin B12 so we need to obtain it through food or supplements.

We need vitamin B12 to make our red blood cells and DNA. It’s also vital for proper neurological function by maintaining healthy nerves and for protecting our cardiovascular function by helping to remove a harmful protein called homocysteine that can damage our arteries if left to travel through the bloodstream. Vitamin B12 also supports our energy production by participating in various chemical reactions that release energy from the food we eat.

How much vitamin B12 do I need?

Below is a table with the current Recommended Dietary Allowances (RDAs) for vitamin B12 in South Africa. For infants aged 0-12 months, these values are Adequate Intakes (AIs) as no RDAs have been established. AIs are based on the average intake of vitamin B12 in healthy populations.

Table 1 vitamin B12

Table 1 – Adapted from The Nutrition Information Centre of the University of Stellenbosch. Recommended Dietary Allowances (RDAs) for vitamin B12 among different age groups in South Africa.

As I pointed out in my previous article on iodine, we have to be cautious in relation to RDAs. They are based on the ‘average’ and what one person requires to prevent deficiency might not be enough for another person. Therefore, they should only be used as a reference. This is particularly pertinent for vitamin B12 since absorption is a major factor as I’ll discuss below.

Vitamin B12 deficiency

A lack of vitamin B12 occurs when our body doesn’t get enough vitamin B12 through our diet or if our body cannot absorb enough of it to be healthy.

To absorb vitamin B12, we need to have a normal functioning digestive system, including adequate acid secretion and the production of a compound called intrinsic factor in the stomach. We also need a healthy small intestine. I say this because vitamin B12 binds to protein in foods and needs to be released with the help of our stomach acid. It then has to bind to intrinsic factor in order to be absorbed in the small intestine. The absence of intrinsic factor results in very poor vitamin B12 absorption.

Having low stomach acid levels and digestive enzyme secretions, a condition called hypochloridia, is very common nowadays. The older you are, the more likely you are to have low levels. But the stress from modern-day life can also be a factor. As younger people are increasingly suffering from this condition, this also puts them at a high risk of vitamin B12 deficiency. Individuals who have had surgery to remove part of their gastrointestinal tract or who have a stomach or intestinal disorder, such as coeliac disease or Crohn’s disease, are also more likely to develop vitamin B12 deficiency. Older adults are also at high risk as they tend to eat less, while 10 to 30 per cent of individuals develop atrophic gastritis, an age-related condition of chronic inflammation that decreases the amount of stomach acid secreted, similar to hypochloridia. In addition, people with pernicious anaemia are at great risk of vitamin B12 deficiency as they cannot produce intrinsic factor.

Common symptoms of vitamin B12 deficiency are fatigue, weakness, constipation, reduced appetite and weight loss. Other symptoms include numbness and tingling of the arms and legs, a sore tongue, loss of balance, depression, loss of memory and cognitive function. Vitamin B12 may also result in megaloblastic anaemia, a condition characterised by abnormal red blood cell production.

It’s important to get your vitamin B12 levels checked by your healthcare practitioner as permanent nerve damage can occur if vitamin B12 deficiency is not treated. A more sensitive method is measuring your homocysteine levels as they increase in early vitamin B12 deficiency. It’s also important to monitor folate serum levels as high levels can mask vitamin B12 deficiency.

Vitamin B12 deficiency is normally treated with intramuscular vitamin B12 injections to bypass potential absorption barriers in the gastrointestinal tract. However, oral vitamin B12 supplements in high doses may also be effective. Your healthcare practitioner can determine what should work best for you. As certain medication such as metformin, which is commonly prescribed for diabetic patients, can also interfere with vitamin B12 levels, it’s vital that you discuss what medication you’re taking with your healthcare practitioner.

Vitamin B12 food sources

As I’ve said above, vitamin B12 is naturally found in animal food sources only, such as meat, fish, eggs and dairy products. It isn’t found in plant food sources apart from fortified foods like processed breakfast cereals, plant-based milks and nutritional yeast.

Table 2 Vitamin B12

Table 2 – Adapted from the Vitamin B12 Dietary Supplement Fact Sheet for Health Professionals of the National Institutes of Health. Selected vitamin B12 food sources.

Restrictive vegetarians and vegans should be cautious since their only dietary vitamin B12 sources come from fortified foods. If they rely solely on these, it’s essential that they check food labels to make sure they’re getting enough vitamin B12 (which can be hard). Relying on processed breakfast cereals isn’t a great nutritional choice in my opinion, as they’re probably one of the most popular food sources that are furthest removed from nature. To be on the safe side, restrictive vegetarians and vegans should therefore take a vitamin B12 supplement as there’s no harm in exceeding the recommended daily amounts.