What is Vitamin B12?
Vitamin B12 is one of the B-complex vitamins and can be obtained through dietary intake. Vitamin B12 plays a crucial role in various processes within the human body, including the formation of red blood cells, cell metabolism, central nervous system development, and DNA synthesis.
Within the human body, vitamin B12 serves as a coenzyme to assist in the metabolic reactions of two enzymes. One of these enzymes is methionine synthase, which helps convert homocysteine to essential amino acids, contributing to various biochemical and physiological reactions [1]. Another enzyme is L-methylmalonyl-CoA mutase, which aids in the metabolism of fatty acids [2].
What are the symptoms of vitamin B12 deficiency?
Mild symptoms of vitamin B12 deficiency include glossitis (inflammation of the tongue), fatigue, palpitations, pale skin, and weight loss. In more severe cases, cognitive decline, infertility, and anemia can occur.
B12 deficiency can also manifest neurological symptoms, such as numbness in the hands and feet and tingling sensations in peripheral nerves [3]. These neurological changes may not necessarily coincide with the occurrence of anemia. This implies that by the time anemia due to vitamin B12 deficiency is detected, the body might have been experiencing a prolonged deficiency, potentially leading to irreversible nerve damage. Therefore, early detection and diagnosis of vitamin B12 deficiency are crucial [4].
Our bodies store approximately 1 to 5 milligrams of vitamin B12 in total, gradually depleting over time. As a result, symptoms of vitamin B12 deficiency may take several years to manifest [3].
What are the benefits of vitamin B12?
1. Prevention of Brain Degeneration (Dementia, Cognitive Function, Alzheimer’s Disease)
Excessive deposition of tau protein in the brain leads to abnormal neural cell function, further resulting in conditions such as dementia, memory decline, decreased cognitive abilities, and Alzheimer’s disease [5] [6]. Research indicates that vitamin B12 can inhibit the synthesis of tau protein and prevent its deposition in the brain, thus assisting in the prevention of neurodegenerative diseases in the brain [7].
💡In a clinical study, participants with both dementia or cognitive impairment and low vitamin B12 levels were supplemented with vitamin B12. Significant improvements were observed in their cognitive impairment and language abilities. However, this study did not observe that vitamin B12 could reverse dementia symptoms [8].
💡A retrospective study found a significant positive correlation between lower vitamin B12 concentrations in the body and the occurrence of dementia. When considering both vitamin B12 and folic acid concentrations together in the body, the simultaneous presence of low levels of both vitamins was associated with a significant decline in cognitive abilities [9].
2. Prevention of Cardiovascular Disease and Stroke
Vitamin B12 is involved in the metabolism of homocysteine in the body (related to cardiovascular health). Therefore, many studies support the idea that consuming vitamin B12 can help prevent the occurrence of cardiovascular diseases such as heart attacks and strokes [10]. Additionally, relevant research has confirmed that supplementing with vitamin B12 can lower the concentration of homocysteine in the body [11].
💡In a clinical study, it was found that patients with cardiovascular disease or diabetes who were supplemented with both vitamin B12 and folic acid significantly lowered their homocysteine levels in the body, subsequently reducing the risk of stroke [12].
💡Another analytical study also discovered that a deficiency in vitamin B12 increases the risk of mortality and incidence of cardiovascular disease or diabetes among patients. However, not all research findings support this result, and more comprehensive studies are still needed to confirm the beneficial effects of vitamin B12 in preventing cardiovascular diseases [13].
3. Enhancing Physical Strength
The B-vitamins play a crucial role in energy metabolism within the body, and vitamin B12 is also believed to contribute to enhancing energy metabolism, improving exercise performance, and increasing endurance [1].
💡In a clinical study, supplementation of vitamin B12 to patients with Chronic Obstructive Pulmonary Disease (COPD) resulted in a positive improvement in their exercise tolerance [14].
4. Improving Mood
In recent years, numerous studies have suggested a link between vitamin B12 deficiency and the occurrence of depression or mood disturbances. Some studies have particularly indicated a definite association between depression in older adults and vitamin B12 deficiency [15].
💡An epidemiological study found that community-dwelling elderly individuals with vitamin B12 deficiency had a significantly higher risk of developing depression (this association was observed after excluding factors such as folate concentration and homocysteine levels in the body, focusing solely on vitamin B12 deficiency) [16].
However, it’s important to note that mainstream research still requires further investigation to establish a concrete connection between vitamin B12 and depressive conditions. Nevertheless, these studies suggest that individuals with depressive symptoms should ensure sufficient intake of vitamin B12 [15].
Which Foods Contain Vitamin B12?
Vitamin B12 can only be synthesized by microorganisms, and our bodies are unable to produce it on their own. Therefore, we must obtain sufficient vitamin B12 through our diet. Commonly recognized sources of vitamin B12 include organ meats (especially liver), meat, fish (salmon, tuna), eggs, milk, and dairy products. Plant-based foods generally do not contain vitamin B12 or contain very low amounts [1] [17][1] [17].
The bioavailability of vitamin B12 also varies depending on the type of food source. Vitamin B12 from dairy products, for example, has a higher bioavailability compared to sources from meat and fish [1]. Additionally, the U.S. FDA recommends adding vitamin B12 to grain products to prevent vitamin B12 deficiency [17].
Vitamin B12 Recommended Intake
What is the recommended intake of vitamin B12? According to the Dietary Reference Intakes provided by the Ministry of Health and Welfare, the recommended intake for adults is 2.4 micrograms (µg). For pregnant women, it’s 2.6 µg, and for lactating women, it’s 2.8 µg [17].
| Age | Intake (ug) |
| 1 – 3 | 0.9 |
| 4 – 6 | 1.2 |
| 7 – 9 | 1.5 |
| 10 – 12 | Male: 2, Female: 2.2 |
| 13 – 15 | 2.4 |
| 16 – 18 | 2.4 |
| 19 – 30 | 2.4 |
| 31 – 50 | 2.4 |
| 51 – 70 | 2.4 |
| >=71 | 2.4 |
| Pregnancy | 2.6 |
| breast-feeds | 2.8 |
*Adequate Intakes
Vitamin B12 Side Effects and When to Take It
Vitamin B12 needs to bind with intrinsic factor protein in the stomach before it can be absorbed by the intestines [1]. Therefore, for individuals with digestive issues, it’s recommended to take vitamin B12 after meals for better absorption.
Vitamin B12 is a water-soluble compound, and excess intake is excreted in the urine. It doesn’t accumulate in the body, so there’s no risk of overdosing or serious side effects.
The Institute of Medicine’s Food and Nutrition Board in the United States has stated that vitamin B12 has low potential for toxicity and is generally considered safe. As a result, no tolerable upper intake level (UL) has been established for vitamin B12 [1]. However, taking high doses of vitamin B12 may lead to discomfort, such as headaches, nausea and vomiting, diarrhea, fatigue or weakness, and a tingling sensation in the hands and feet [18].
Some medications can affect the absorption of vitamin B12. Commonly used gastric acid suppressants (primarily used to treat gastroesophageal reflux disease and stomach ulcers) can reduce stomach acid release, impacting vitamin B12 absorption. Additionally, a commonly used oral antidiabetic drug, Metformin, can also affect vitamin B12 absorption [1]. Therefore, individuals using such medications should pay attention to their vitamin B12 intake to avoid vitamin B12 deficiency.
