Have You Had Your B12 Test?
What Are B-Complex Vitamins? What Do They Do?
B vitamins consist of eight essential vitamins involved in processes such as the body's energy metabolism, cell function and blood cell production: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B9 (folate) and B12 (cobalamin).
These vitamins help the body use nutrients in energy metabolism; however, taking them as supplements does not guarantee increased energy or improved stress management in people without a deficiency. Most people can meet their requirements through a varied and balanced diet. Supplements should be considered on a doctor's advice, particularly when there is a risk of deficiency or increased requirements.
Functions and Food Sources of B Vitamins
| Vitamin | Some of its main functions in the body | Examples of food sources |
|---|---|---|
| B1 (Thiamine) | Energy metabolism and normal cell function | Whole grains, legumes, meat |
| B2 (Riboflavin) | Energy production and cellular metabolism | Dairy products, eggs, meat, green vegetables |
| B3 (Niacin) | Energy metabolism | Meat, fish, poultry, legumes |
| B5 (Pantothenic acid) | Forms part of coenzyme A; plays a role in metabolic processes | Meat, eggs, legumes, some vegetables |
| B6 | Protein metabolism, production of haemoglobin and certain neurotransmitters | Fish, poultry, potatoes, chickpeas |
| B7 (Biotin) | Fat, carbohydrate and amino acid metabolism | Eggs, meat, fish, seeds and nuts |
| B9 (Folate) | DNA synthesis and cell division; fetal development during pregnancy | Green leafy vegetables, legumes, fortified grains |
| B12 (Cobalamin) | Nervous system function, DNA and blood cell production | Meat, fish, eggs, dairy products; also some products fortified with B12 |
The food sources in the table are examples; the amounts in foods and the body's absorption can vary from person to person. B12 occurs naturally mainly in animal-based foods. People following a vegan diet and those with certain health conditions or taking medications that may affect B12 absorption can therefore discuss their risk of deficiency with a doctor.
Who May Develop B Vitamin Deficiency?
B vitamin deficiencies can develop for various reasons, and their symptoms vary depending on which vitamin is deficient. Signs and symptoms such as anaemia, fatigue, tongue tenderness, and numbness or tingling in the hands and feet can have different causes and do not, on their own, indicate a B vitamin deficiency.
The risk of B12 deficiency may increase in situations such as a vegan diet, certain gastrointestinal diseases or surgeries, pernicious anaemia, and long-term use of metformin or medicines that reduce stomach acid. Neurological symptoms related to B12 deficiency can also occur without anaemia. Therefore, if risk factors or symptoms are present, assessment should be planned by a doctor.
Are “Active Form” B Vitamins Always Better?
B vitamins occur in different chemical forms in the body; some forms function as coenzymes. However, this does not mean that everyone needs to use only supplements marketed as “active”. For example, current evidence does not show that absorption of B12 supplements varies according to the form of the vitamin. Common MTHFR gene variants also do not mean that a person cannot use folic acid.
For people planning a pregnancy or who could become pregnant, 400 micrograms of folic acid daily is recommended to reduce the risk of neural tube defects. The folic acid recommendation still applies even if an MTHFR variant is present; a doctor determines whether a higher dose is needed in certain specific circumstances.
B Vitamins, Homocysteine and Cardiovascular Disease
B6, B9 and B12 play a role in homocysteine metabolism. Supplementation with these vitamins may lower homocysteine levels; however, this reduction alone has not been shown to reduce the risk of heart attack or stroke. Elevated homocysteine can occur for various reasons, and the result should be assessed in the context of the clinical situation.
Are B-Complex Supplements Safe?
Most B vitamins are water-soluble; however, this does not mean that high doses are always harmless. Long-term use of high-dose B6 can cause nerve damage and numbness or tingling. High-dose niacin can cause side effects, while excess folic acid can mask some blood-related signs of B12 deficiency, making assessment more difficult. High-dose supplements containing biotin can also interfere with certain laboratory tests. If you take supplements, inform your doctor and the laboratory before a blood test.
B Vitamin Tests
No single test measures the levels of all B vitamins. Which vitamin to measure is determined by the person's symptoms, diet, health status and medications. For example, Wellcare check-up packages may include B12 and folate tests, depending on the contents of the selected package.