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Vegetarians and vegans need to focus more on vitamin B12, vitamin D, iodine, iron, and selenium

Vegetarians and vegans need to focus more on vitamin B12, vitamin D, iodine, iron, and seleniumMore and more people in the Western world shift to a plant-based diet but may find themselves challenged when it comes to getting enough of certain essential nutrients. A new German study shows that most vegetarians and vegans get enough vitamin B12, provided they take supplements. However, many lack iodine and iron. Also, plant-based diet fails to deliver enough vitamin D, and many lack selenium due to the nutrient-depleted farmland. A lot of deficiency diseases are insidious, which makes it difficult to link them to the diet. It is therefore a good idea for children and adults who are vegetarians or vegans to take relevant supplements.

A varied plant-based diet provides a lot of vitamin C, vitamin E, most B vitamins, potassium, magnesium, dietary fiber, and secondary plant compounds that are good for you. An American study of Seventh Day Adventists has demonstrated that their plant-based diet (both vegetarian and vegan) lowers the risk of overweight, hypertension, type 2 diabetes, cardiovascular disease, and cancer, even after adjusting for factors like smoking and BMI (body mass index). But the jury is still out on whether or not vegetarian or vegan diets are linked to specific health risks.
The number of vegetarians and vegans in Germany is increasing. Therefore, a group of German scientists decided to look closer at the relation by collecting data from a large study of advantages and disadvantages of vegan diets. The scientists looked closely at diet habits, lab tests, vitamin status and mineral status in 36 vegans and 36 people on normal diets. Each group consisted of 18 men and 18 women aged 30-60 years. Nearly all vegans and one third of the controls had taken supplements within the previous four weeks.

Lack of nutrients and important supplements

It turned out that both groups had similar vitamin B status. Because vegan diets do not contain vitamin B12, the scientists assumed that nearly all vegans were in the habit of taking a supplement. Both groups got too little iodine. The deficiency among vegans was alarming. Also, there was iron deficiency in both groups, especially among the vegans.
Because the sun is our most important source of vitamin D, not the diet, the scientists did not find any difference in vitamin D status among the two groups. Still, most people need to take a vitamin D supplement during the winter period where the sun is too weak to enable the body to synthesize the vitamin.
The vegans also had less selenium in their blood compared with the control group. The scientists used selenoprotein P as a marker to establish selenium status. They refer to other studies that show widespread selenium deficiency in Europe because of the selenium-depleted farmland. The researchers recommend selenium supplements but warn against excess intake, as selenium can be toxic in large quantities. The European Food Safety Authority (EFSA) has established a safe upper daily intake level of 300 micrograms.
The new German study is published in the scientific journal Deutsche Ärzteblatt. Its results support an earlier study from the University of Copenhagen where scientists compared 70 Danish vegans aged 18-61 years with 1,257 regular meat eaters. The study revealed that the vegans got too little protein, vitamin D, iodine, and selenium. Other studies show that vegetarians and vegans also lack vitamin B12 if they don’t take supplements. So, what do all these different deficiencies mean for our health?

  • Meat, offal, and fish provide complete proteins, vitamins, minerals, and essential fatty acids that vegetarians and vegans may have difficulty with getting in sufficient amounts
  • For vegetarians and vegans, it takes quite a lot of knowledge about diet to get enough of all the essential nutrients


Too little protein and lack of essential amino acids may cause problems like unstable blood sugar, tiredness, sleep disturbances, overweight, impaired immunity, muscle weakness, and problems with skin, hair, and nails.

Vitamin B12

Deficiency symptoms can be insidious and include anemia, paleness, and fatigue. Also, there can be symptoms from the nervous system such as poor memory, dementia, muscle weakness, and nerve infection. Lack of vitamin B12 can also damage the growth and learning ability of children.
It is recommended for vegetarians and vegans to take a vitamin B12 supplement.

Vitamin D

Lack of vitamin D increases the risk of infections, inflammation, osteoporosis, cancer, and numerous other symptoms because all cells in the body need this vitamin. During the summer period, adequate sun exposure will cover your need for vitamin D. During the winter period, it is advised to take a supplement.


Lack of iodine may cause thyroid disorders and increased risk of breast cancer. Iodine deficiency during pregnancy increases the risk of having a retarded child.


Iron deficiency typically causes paleness because of anemia. It can also cause symptoms like fatigue, dizziness, heart palpitations, impaired immunity, and changes to the skin, hair, and nails. In children, iron deficiency may cause stunted growth and learning difficulty. Women of childbearing age are especially likely to lack iron due to menstrual bleeding.


Selenium deficiency increases the risk of decreased fertility, cardiovascular disease and cancer. There is also an increased risk of thyroid disorders, infections, inflammation, and cataracts.

The Danish Veterinary and Food Administration recommends the following supplements for vegans:

  • 10 micrograms of vitamin D daily during the winter (from October to April)
  • 2 micrograms of vitamin B12 daily

Depending on one’s diet, it may also be relevant to take the following nutrients:

  • Iodine
  • Iron
  • Selenium
  • Zinc

Vegetarians may also need the above listed supplements. It is normally enough to take a high-quality multivitamin and mineral supplement with good bioavailability.

The Danish Veterinary and Food Administration has the following recommendations for children and pregnant women:

Children up to the age of 2 years:

  • Pregnant women on a vegan diet should take a vitamin B12 supplement throughout their pregnancy and as long as they breastfeed
  • Pay special attention to the growth of the child
  • The child must be given certain nutritional supplements
  • The parents should consult with an authorized dietician

Children older than 2 years:

  • The child should be given a multivitamin tablet that contains vitamin B12 and vitamin D
  • The parents should consult with an authorized dietician


Weikert C et al. Vitamin and Mineral Status in a Vegan Diet. Deutsches Ärzteblatt Online. November, 2020

BfR Federal Institute for Risk Assessment. Veganism: Vitamin B 12 is well supplemented, iodine is a matter of concern. Science Daily, November 10, 2020

Else Molander. Anbefalinger vedr. vegansk kost. Fødevarestyrelsen. Januar 2019
Nordiske Næringsstofanbefalinger

Ulla Gjeset Schølberg. Veganere mangler vitaminer og mineraler. 2016

Asoc C. Antony. Vegetarianism and B-12 (cobalamin) deficiency. The American Journal of Clinical Nutrition 2013

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