Vitamin B12, (Part 2) - Vitamin B12 Deficiency

Vitamin B12 Deficiency

Vitamin B12 is an essential nutrient that we have to take in through our food. According to the American Society for Nutrition (ASN), the recommended daily intake is 4 µg. Since this vitamin is only found in foods of animal origin, vegetarians and vegans in particular have an increased risk of vitamin B12 deficiency. However, due to the complex absorption mechanism of the vitamin, which we described in our previous vitamin B12 article, non-vegetarians are also often affected. There are many reasons for a deficiency and the health consequences can be just as far-reaching. In this article you will learn more about the causes and symptoms of a B12 deficiency.

This article describes the risks, symptoms, and causes of deficiency. If you want to learn more about absorption, take a look at part 1 of our vitamin B12 series.

Causes of Vitamin B12 Deficiency

Low intake

A vitamin B12 deficiency can be caused by low intake, decreased absorption or an increased need. A low intake that leads to inadequate B12 levels can occur in particular with a vegan or plant-based diet. Since B12 is the only nutrient found exclusively in animal foods, vegans are strongly recommended to regularly take a dietary supplement or consume fortified foods. Vegetarians who rarely consume dairy products or eggs can also benefit from a vitamin B12 supplement. In short, dietary supplements and fortified foods are the only reliable alternatives to animal foods.

Our liver can store excess B12, and the liver stores are sufficient for about a year. This means that vegans have to start taking B12 supplementation after a year at the latest.

There can also be a nutritional deficiency due to malnutrition, especially in risk groups such as the elderly. Those with anorexia or chronic alcoholism also run the risk of not getting enough B vitamins.

Increased need

Pregnant and breastfeeding women have a higher need for vitamin B12. You need about 4.5 or 5.5 µg daily to support the growth of your baby. Pregnant and breastfeeding mothers on a vegan diet in particular can risk symptoms of deficiency in their infants if they do not meet their nutritional needs. Mothers who do not include enough B12-containing foods in their diet should take a dietary supplement.

Poor digestion

While some people consume enough foods rich in vitamin B12, they are still prone to deficiency because their digestive systems cannot properly absorb the suppliment. There are many causes for this problem that can be divided into two categories. On the one hand, food can no longer be broken down and digested properly due to maldigestion and, on the other hand, malabsorption means that nutrients in the intestine can no longer be properly absorbed. Both types of indigestion can lead to vitamin B12 deficiency.


Natural vitamin B12 found in food sources is bound to proteins. In order for the vitamin to be transported and absorbed in the intestine, however, our body must first detach it from the proteins. Since stomach acid helps break down the B12-protein bonds, decreased stomach acid production can interfere with the complete digestion of foods rich in B12. In addition, pancreatic enzymes help break down and transport vitamin B12 from food. Accordingly, a reduced pancreatic function can also lead to a vitamin B12 deficiency. Fortunately, vitamin B12 in dietary supplements and fortified foods is not bound to proteins and can usually be absorbed without any problems despite maldigestion.


In order for the vitamine to be absorbed into the bloodstream through the intestines, a protein called intrinsic factor (IF) is required. This protein is produced in the stomach and binds to vitamin B12. Vitamin B12 can only be recognized and absorbed through this IF-B12 complex.

Malabsorption of occurs in some people who are unable to produce enough IF. Inflammation in the small intestine can cause malabsorption by reducing the area of ​​absorption. This is often the case in people who have inflammatory diseases such as celiac disease or Crohn's disease. Operations on the stomach or small intestine can also reduce the absorption of by reducing IF production or the absorption area.

In contrast to maldigestion, a dietary supplement can unfortunately not help with an absorption disorder. Instead, an intramuscular injection given by the doctor can ensure the supply of vitamin B12.


How Vitamin B12 Deficiency Affects the Body
How Vitamin B12 Deficiency Affects the Body

Low levels can lead to a variety of symptoms, depending on their severity. However, many symptoms take a long time to show up. In order to avoid permanent damage, it is therefore important to intervene early and remedy the cause of the deficiency.

If left untreated, deficiency can cause what is known as megaloblastic anemia. Anemia is a disease in which the blood cannot carry enough oxygen and the total number of healthy red blood cells is reduced.

Symptoms of megaloblastic anemia include:

  1. Fatigue
  2. Low appetite
  3. Weakness
  4. Headache
  5. Pale skin
  6. Diarrhea
  7. Constipation

In addition to anemia, a deficiency in can also cause neurological disorders. Signs of neurological damage are seen in around 20-30% of patients with vitamin B12 deficiency. The symptoms can occur independently of anemia.

Symptoms from neurological damage include:

  1. Reduced cognitive performance.
  2. Apathy.
  3. Depressions.
  4. listlessness.
  5. Psychosis.
  6. Bad memory.
  7. Dementia.
  8. Numbness and tingling in hands and feet.

Children with a deficiency run the risk of impaired growth and cognitive development. Low levels are also linked to cognitive decline in the elderly. However, many of the symptoms of megaloblastic anemia and neurological damage are non-specific and can also be caused by conditions unrelated to deficiency.


Several population groups are at increased risk of deficiency:

Vegans and vegetarians, the elderly, people suffering from gastrointestinal diseases, pregnant women and newborns.

It is important not to wait so long for symptoms to appear, but to take action beforehand. Check out the next article in our Vitamin B12 series to find out which foods are particularly high in B12 nd to read our detailed supplement guide.

If you are unsure of your vitamin B12 supply, a blood test is a good way to determine if you are at risk of deficiency. Routine checkups are especially important for those with Celiac disease and Crohn's disease.


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