Why the body needs vitamin B12
Vitamin B12 is actually a whole group of essential vitamins, also called cobalamins. These are important for
the production of genetic material in our cells, i.e. for growth and development
the formation of red blood cells
the function of the nervous system
the absorption of folic acid and carbohydrates in our food
vitamin B12 also plays a role in homocysteine metabolism. Homocysteine is considered a risk factor for arteriosclerosis and cardiovascular diseases
A vitamin B12 deficiency can lead to a specific form of anaemia and nerve damage. In some cases, the damage is permanent.
Typical symptoms of a deficiency
If the vitamin B12 deficiency is mild, there are usually no symptoms. However, if the deficiency is severe, the following symptoms may appear:
- burning tongue
- unsteadiness when walking
- tingling in hands and feet
- memory problems
- depressive mood
Why a deficiency can develop almost unnoticed
The liver and some of the body's muscles can store vitamin B12. Up to 5 milligrams can be found in the body, forming a supply that lasts for several years. This means that if too little of the vitamin is obtained through food, the body will first tap into its own reserves. It can take months or even years before a deficiency becomes apparent.
Daily requirement of vitamin B12
The reference values* have been adjusted according to current scientific data and depend on the person’s age. This means that daily requirements change during the course of childhood:
- it increases from 0.5 micrograms (µg) for infants to 3.5 µg for 12-year-olds.
- from the age of 13 and for adults, 4 µg is recommended.
- pregnant and breastfeeding women require 5.5 µg.
* According to the Deutsche Gesellschaft für Ernährung (German Nutrition Society), vitamin B12 requirements cannot be determined exactly. The new reference values are therefore estimates of what is deemed to be an adequate intake.
Vitamin B12 deficiency levels
To detect a deficiency, the overall B12 level in the blood is measured. If this is less than 150 pmol/l, treatment is advised. However, because the test is considered inconclusive, it is useful to also measure holotranscobalamin (holo-TC) and methylmalonic acid (MMA) levels.
Vitamin B12 injection or tablets
If a person’s vitamin B12 intake is deficient, tablets are usually prescribed. If their absorption of vitamin B12 is the problem, treatment by injection is an option. Depending on the cause of the deficiency, treatment may be necessary for the rest of their life.
Vitamin B12 deficiency due to the wrong eating habits – a mass phenomenon?
It would be easy to get this impression, since there's a lot of reporting about vitamin B12 today, especially in connection with dietary trends. The fact is, however, that we can usually easily cover our daily requirement with food, provided we eat a balanced diet.
- Those who follow the recommendations of the Swiss Food Pyramid consume about 10 micrograms of vitamin B12 a day.
- However, some population groups have to be careful, either because their bodies cannot absorb enough vitamin B12, or because they get too little through their diet.
- Special recommendations apply to vegans.
Foods with vitamin B12
According to the latest research, vitamin B12 can be absorbed through foods such as meat, fish, seafood, eggs and dairy products. The following is a selection:
- 100g beef or veal liver: 60 bis 65 µg
- 100g lamb liver: 35 µg
- 100g caviar: 16 µg
- 100g oysters: 14.5 µg
- 100g rabbit: 10 µg
- 100g mackerel: 9 µg
- 100g mussels: 8.5 µg
- 100g lean beef: 5 µg
- 100g trout: 4.5 µg
- 100g Emmental or Camembert cheese: 3.1 µg
- 100g cooked salmon: 2.9 µg
- 100g mozzarella: 2 µg
- 1 cooked egg: 1.1 µg
- 3 heaped tablespoons of quark: 0.7 µg
- 1 small glass of cow's milk: 0.6 µg
- 1 small pot of yoghurt: 0.6 µg
- 60g cream cheese: 0.3 µg
Almost all animals depend on a supply of vitamin B12 through what they feed on. In livestock farming, however, this can become a problem, such as when ruminants don’t get enough cobalt to form vitamin B12. Artificial vitamin supplements are therefore mixed into the fodder. As a result, those who cover their vitamin B12 needs with animal products are in many cases ingesting the vitamin B12 that has been added to the animal feed.
There is no harm in consuming too much of the water-soluble vitamin B12 through food. Superfluous amounts are discharged through the urine. Before resorting to supplements, it’s advisable to consult a doctor.
Vitamin B12 in plant foods
Vitamin B12 is produced exclusively by micro-organisms and is found almost exclusively in animal foods. We often read that other good sources include fermented soy products, sauerkraut or beer; plus, sea buckthorn or tuber and root vegetables with soil still sticking to them. Nonetheless:
- the small amounts of vitamin B12 in plant foods are not enough to meet the body's needs. It's also unclear whether the form of vitamin B12 it contains can be metabolised by humans. The same applies to seaweed such as nori.
- spirulina and other products with cyanobacteria, which are marketed as good sources, are also ineffective. The vitamin analogues in them may even be harmful because they interfere with the absorption of true vitamin B12.
- studies indicate that shiitake mushrooms contain vitamin B12. However, the content can vary greatly.
Why fortified foods aren't enough
Cornflakes, juice, soy milk, vegan meat substitutes: there are now a number of foods that are fortified with synthetic vitamin B12.
- According to the Vegan Society of Switzerland, however, the quantities in them are small for legal reasons. It is therefore difficult to obtain a sufficient dosage.
- Vitamin B12-enriched toothpaste, which has been on the market for a few years, is also an unreliable source of supply.
Who else should pay attention
Vegetarians whose diet contains only a very small portion of animal foods should also have their vitamin B12 levels checked regularly. This is especially true for pregnant and lactating vegetarians, as their nutrient requirements are higher.
The consequences of a vitamin B12-deficient diet
An adequate vitamin B12 intake is particularly important for babies, children and adolescents, i.e. during growth phases. And also for women who are pregnant or breast-feeding, because babies need their own supply too. Authorities advise against eating a vegan diet during these «sensitive phases of life», for reasons that include:
- a vitamin B12 deficiency before pregnancy is deemed an independent risk factor for miscarriage or pre-eclampsia.
- newborns may have lower weight or neural tube defects.
- young children may suffer permanent neurological damage.
Important note: women who are pregnant or breast-feeding are best advised to consult their gynaecologist for information on special diets and nutrient supplements.
- Swiss Society for Nutrition, SSN
- German Nutrition Society, DGE
- Federal Food Safety and Veterinary Office, FSVO
- Vegane Gesellschaft Schweiz (Vegan Society of Switzerland)