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Depression may be linked to vitamin B12 deficiency

Depression may be linked to vitamin B12 deficiencyVitamin B12 is involved in the making of red blood cells. Its role in our nervous system is often overlooked. According to a large Irish study of older people that is published in British Journal of Nutrition, there is a link between lacking vitamin B12 and feeling depressed. Depression is a growing problem that comes with a huge human and socioeconomic price tag, which makes this study highly relevant. It is especially older people, public health servants, and politicians that should pay extra attention to vitamin B12 deficiencies and how to prevent them with simple and inexpensive means. It should also be noted that vegetarian and vegan diets, low stomach acid, and diabetes medication can increase the risk of having low levels of vitamin B12.

We need vitamin B12 in order to produce red blood cells. The vitamin also supports our energy levels, our nervous system, our brain, and our cell division. The vitamin is only found in animal sources such as meat, fish, eggs, and dairy products. Our stomach acid helps release vitamin B12 from food so it becomes easier for the small intestine to absorb the nutrient, helped by a carrier called intrinsic factor. Vitamin B12 is stored in the liver which means months or even years can go by before you notice deficiency symptoms caused by things like eating a strictly plant-based diet, having absorption issues, using certain types of medication, or perhaps other reasons.

Older people and their vitamin B status

It is quite common for older people to have low levels of B vitamins such as folic acid and B12. In Ireland, it is reported that one in eight seniors has low vitamin B12 status. Deficiencies have also been observed in other age groups and it is probably the same in Denmark. It is commonly known that a vitamin B12 deficiency can cause two types of anemia: pernicious anemia and megaloblastic anemia. Other symptoms may occur such as cognitive impairment (resembles dementia), or damage to the protective myelin sheaths that coat the brain neurons. Because vitamin B12 has such an important role in our nervous system it is vital to find out if it is a nutrient deficiency that causes depression. Just for the record, depressions are associated with impaired quality of life and an increased need for assistance to get along on a day-to-day basis. Some people are admitted to nursing homes, and there is even a risk of early death.

The most important results from the study

The scientists looked at data from a large Irish population study named TILDA (The Irish Longitudinal Study on Ageing). More specifically, they looked at people older than 50 years of age who were living on their own. Blood levels of folic acid and vitamin B12 were measured in all participants and they were also tested for depression. The study data revealed that the participants who lacked vitamin B12 were 51 percent more likely to develop a depression in the course of the four-year study period. The scientists underpinned the following:

  • The study showed that low levels of vitamin B12 significantly increase the risk of depression. A similar link was not observed with low folic acid levels
  • Lack of vitamin B12 increased the risk of depression by 51% in the course of the four-year study period
  • The results prevailed even after adjusting for confounding factors like physical activity, chronic illness, vitamin D levels, and the use of anti-depressive medication
  • The scientists observed that the risk of developing a depression increases with age
  • The study is very relevant because it links ageing to low vitamin B12 status and an increased risk of developing a depression
  • The study suggests that an updated food policy and the introduction of vitamin B12 enrichment of certain foods may help prevent vitamin B12 deficiencies

Treating vitamin B12 deficiency with high-quality supplements

When people are severely vitamin B12-deficient, injections of the nutrient can offer fast relief of various symptoms. If the vitamin B12 deficiency is related to the diet it may be necessary to make dietary changes or perhaps even start taking a supplement. Vitamin B12 lozenges give better absorption because the nutrient is absorbed directly by the oral mucosa. A supplement should contain at least 2.5 micrograms of vitamin B12 (equivalent to the daily reference intake level). To treat pernicious anemia, a lifelong disease, one must use continuous vitamin B12 injections due to the body’s lack of intrinsic factor, the carrier that helps the body absorb vitamin B12 in the small intestine.

Who is most likely to lack vitamin B12?

  • Older people
  • Vegans and vegetarians
  • People with low stomach acid (that reduces the uptake)
  • People who use antacids
  • Diabetics, especially because of their use of metformin
  • Patients with chronic intestinal diseases
  • People who have undergone gastric by-pass surgery

How to measure levels of vitamin B12

The physician normally takes a blood sample to test levels of vitamin B12. It is always important to inform your doctor about any use of medicine or supplements that may affect the outcome.


Trinity College Dublin. Vitamin B12 Deficiency Associated With Depression Risk in Longitudinal Study. Neuroscience News & Research. 2021

Laird E, O´Halloran AM et al. Low vitamin B12 but not folate is associated with incident depressive symptoms in community-dwelling older adults: a 4-year longitudinal study. British Journal of Nutrition. December 13, 2021.

Jayne Leonard. What is the purpose of a vitamin B12-level test? MedicalNewsToday. 2020

Vanita R Aroda et al. Long-Term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study. Endocrine Society 2016

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