Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for various bodily functions, including DNA synthesis, red blood cell production, energy creation, and maintaining a healthy brain and nervous system. It may even affect your mood and memory. A deficiency in this nutrient can have debilitating health effects. While some suggest unwanted weight gain could be a side effect of B12 deficiency, scientific evidence presents a more nuanced picture.
Understanding Vitamin B12
Vitamin B12 plays a central role in hematopoiesis and is a component of enzymes, such as methylmalonyl-coenzyme. The body requires an intact stomach and gut, a well-functioning pancreas, and sufficiently high levels of intrinsic factor, a protein that binds to vitamin B12 in the stomach, to absorb vitamin B12 effectively.
Adult women require 2.4 mcg of vitamin B12 per day, increasing to 2.8 mcg per day during pregnancy and breastfeeding. Adult men can meet their needs by consuming 2.6 mcg of vitamin B12 per day. Extra vitamin B12 can be stored in the liver, with only small amounts lost daily through urine, sweat, or stools. Due to this and the small daily requirements, it can take a year or longer of insufficient vitamin B12 intake to develop an overt deficiency.
Symptoms of Vitamin B12 Deficiency
Once present, vitamin B12 deficiency can manifest in various ways:
- Chronic fatigue
- Shortness of breath
- Heart palpitations
- Tingling or numbness in the extremities
- Poor balance
- Loss of concentration
- Poor memory
- Disorientation
- Mood changes
- Incontinence
- Insomnia
- Pale or yellowish skin
Risk Factors for Vitamin B12 Deficiency
Certain populations are more susceptible to developing a vitamin B12 deficiency:
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- Older adults
- Those who smoke or abuse alcohol
- Vegetarians and vegans
- Individuals who have undergone gut surgery
- Those with pancreatic insufficiency
- Those with small intestinal bacterial overgrowth (SIBO)
- Individuals with parasite infections
- Those with certain autoimmune disorders
Certain medications, including metformin, proton pump inhibitors, and antacids, may also reduce your body’s ability to absorb vitamin B12 from your diet.
Vitamin B12 and Weight: Separating Fact from Fiction
Despite the numerous processes in which vitamin B12 is involved, there’s little evidence to suggest that it has any influence on weight gain or loss.
Most of the evidence giving rise to this claim comes from a few observational studies. For instance, one study notes that people with excess weight or obesity appear to have lower vitamin B12 levels than people who have a body mass index (BMI) in the “normal” range. Additional research has observed that people who voluntarily took vitamin B12 supplements gained between 2.5-17 fewer pounds (1.2-7.7 kg) over 10 years than those who did not supplement with this vitamin. Still, such observational studies cannot confirm whether low vitamin B12 levels are what caused the weight gain, nor whether they’re what protected against low levels.
On the other hand, a vitamin B12 deficiency appears to cause a loss of appetite in some people, leading to weight loss rather than weight gain. That said, the current evidence is too weak to suggest that a vitamin B12 deficiency has any strong or specific impact on weight - be it weight gain or loss.
The Functional Medicine Perspective
From a functional medicine perspective, vitamin B12 is crucial for the body's metabolism, particularly in energy production at the cellular level. Our cells need energy to function, which is produced in the mitochondria, the "powerhouse" of the cell. B12 plays a vital role in the production of red blood cells, which carry oxygen throughout our bodies. Without enough oxygen, this process is hindered, and fat burning slows down.
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Dietary Sources and Supplementation of Vitamin B12
Vitamin B12 is found exclusively in animal foods or foods fortified with this vitamin.
Animal Sources
- Meat and chicken: especially organ meat and red meat like beef
- Fish and seafood: especially clams, sardines, tuna, trout, and salmon
- Dairy: including milk, cheese, and yogurt
- Eggs: especially egg yolk
Fortified Foods
- Breakfast cereal
- Nutritional yeast
- Some mock meats or plant milks
Supplements, widely available in stores and online, are another way to meet your daily requirements. They’re especially handy for people with low levels of intrinsic factor, a protein that helps your body absorb vitamin B12 more easily. Additionally, they can help those who have difficulty consuming sufficient amounts of the foods above meet their daily vitamin B12 needs. This may include vegetarians or vegans who don’t plan their diet carefully.
The Link Between Vitamin B12 and Thyroid Disorders
Numerous studies have found an association between vitamin deficiency and thyroid disorders (TD). The presence of anti-parietal cell antibodies is indicative of a reduced ability to absorb vitamin B12. Patients with hypothyroidism had lower vitamin B12 levels than healthy participants (MD: −60.67 pg/mL; 95% CI: −107.31 to −14.03 pg/mL; p = 0.01). No significant differences in vitamin B12 levels were observed between healthy participants and patients with hyperthyroidism (p = 0.78), autoimmune thyroid disease (AITD) (p = 0.22), or subclinical hypothyroidism (SH) (p = 0.79).
Thyroid disorders (TD) are a heterogeneous group of diseases that affect the thyroid’s anatomy or function, including hypothyroidism, hyperthyroidism, subclinical hypothyroidism (SH), subclinical hyperthyroidism, structural abnormalities, and cancer. The increasing life expectancy of the global population has significantly increased the incidence of TD and its global burden, especially among older adults. Thyroid function is regulated by various nutrients, primarily iodine and selenium. Certain vitamins also play moderating roles in thyroid function, such as vitamins A, E, D, and B. Previous studies have reported vitamin deficiencies in patients with TD.
Research Findings
A systematic review was conducted to evaluate the differences in the serum levels of vitamin B12 among patients with and without TD. The secondary objectives were to evaluate the frequency of vitamin B12 deficiency in patients with TD and the frequency of APCA in patients with autoimmune thyroid diseases (AITD).
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The main finding of the study was the significant difference in the vitamin B12 levels between patients with hypothyroidism and healthy participants. However, no significant difference was observed in the vitamin B12 levels between patients with hyperthyroidism/AITD/SH and healthy participants. The frequencies of vitamin B12 deficiency in patients with SH, hypothyroidism, hyperthyroidism, and AITD were 27%, 27%, 6%, and 18%, respectively, and the frequency of APCA in AITD was 27%.
Potential Causes of Vitamin B12 Deficiency in Thyroid Disorders
Inadequate dietary intake and malabsorption are the major causes of vitamin B12 deficiency, though the first rarely occurs in high-income countries, as foods of animal origin are an important component of the diet. B12 malabsorption is found in some medical conditions such as AAG, Helicobacter pylori infection, PA, and long-term antacid treatment.
The association between vitamin B12 deficiency and TD has been studied with a particular focus on patients with AITD. AITD encompasses a group of disorders characterized by the production of antibodies against the thyroid gland, with Graves’ disease and Hashimoto’s thyroiditis being the most common. The causes of vitamin B12 deficiency among these patients are likely to be multifactorial, predominantly related to the comorbidity of other autoimmune disorders, such as AAG, PA, and celiac disease.
In the absence of AITD, the causes of vitamin B12 deficiency in those with hypothyroidism have been studied in less detail; however, they might be related to dietary habits. Alterations in the composition of the microbiota, bacterial overgrowth, and slow intestinal motility have also been proposed as potential causes in these patients.
Study on Hypothyroid Patients
A single-centric cross-sectional study was carried out over a period of one year. Among 100 hypothyroid patients, 68% were found to be vitamin B12 deficient, among whom 73.5% were females. Of patients with raised anti-TPO antibodies, 78.6% had vitamin B12 deficiency (p = 0.01), while 78% of patients with raised anti-Tg antibodies were vitamin B12 deficient (p = 0.07). There is a predilection of hypothyroid patients toward developing anemia, with vitamin B12 deficiency as a major etiology.
The study included 100 hypothyroid patients, and serum vitamin B12 levels were investigated and correlated with the presence of thyroid autoantibodies. The most common presenting complaint in the hypothyroid population was weakness (56%), followed by weight gain (50%). A total of 24% of hypothyroid patients in this study had moderate anemia, with 42% of patients suffering from severe anemia (p = 0.29). Of hypothyroid patients included in the study, 53% had a macrocytic blood picture, signifying a probable cause of vitamin B12 deficiency.
The Pearson correlation coefficient (r) between vitamin B12 and anti-TPO antibody was -0.302, showing a negative correlation between vitamin B12 and anti-TPO antibody levels (r (98) = 0.302, p = 0.002), i.e., a rising anti-TPO antibody level with declining serum vitamin B12 levels. On the other hand, the Pearson correlation coefficient (r) between TSH and serum vitamin B12 was -0.084, showing a small negative correlation between vitamin B12 and TSH (r (98) = 0.084, p = 0.406), which was, however, statistically non-significant.
Implications and Management
Taken together, the results of the study on a general population of outpatients and inpatients of hypothyroidism prove to be consistent with our hypothesis based on evidence-based literature, stating that there is a predilection of hypothyroid patients toward developing anemia, with vitamin B12 deficiency as a major etiology. Therefore, megaloblastic anemia being present in patients with hypothyroidism, the clinical manifestations and severity of hypothyroidism can have a balanced input from both hypothyroidism and a deficiency of vitamin B12.
Clinical manifestations of both hypothyroidism and vitamin B12 deficiency are interlinked, with a lot of signs and symptoms overlapping between the two diseases. It has been observed that even after adequate supplementation of exogenous thyroxine, symptom alleviation may not be achieved in a hypothyroid individual. In such cases, supplementation of vitamin B12 in adequate doses in hypothyroid patients might help in mitigation of symptoms and decrease in severity of the disease.
Vitamin B12 Shots and Weight Loss: A Closer Look
Vitamin B12 shots help you lose weight claims flood social media and wellness blogs, but the scientific evidence tells a different story. B12 shots only help with weight loss if you have a B12 deficiency. No solid proof exists that B12 shots cause weight loss in people with normal levels. They may boost energy and metabolism only when correcting a deficiency.
The reality is that up to 15% of people may have vitamin B12 deficiency, which can impact weight-loss efforts due to fatigue and slowed metabolism. A 2019 study found that people with obesity had lower B12 levels than those at moderate weight, but this doesn’t prove that B12 supplementation causes weight loss.
How Vitamin B12 Shots Might Indirectly Support Weight Management
While direct evidence is lacking, researchers have proposed several mechanisms by which B12 might indirectly support weight management:
- Lipid Metabolism Improvement: B12 plays a role in breaking down fatty acids through its involvement in methylmalonyl-CoA mutase, an enzyme crucial for fat metabolism.
- Mitochondrial Function: Mitochondria need B12 to produce energy efficiently.
- Indirect Energy Increase: When B12 deficiency causes fatigue, correcting the deficiency can restore energy levels, leading to increased physical activity and higher calorie burn.
- Mood and Motivation: B12 deficiency can cause depression and brain fog. Restoring normal levels may improve mood and motivation, making it easier to stick to diet and exercise plans.
Who Might Benefit from B12 Injections?
People with documented B12 deficiency (blood levels below 200-300 pg/mL) are the clearest candidates. Pernicious anemia is another strong indication for injections. We also see excellent results in patients with malabsorption disorders like Crohn’s disease or celiac disease. Similarly, if you’ve had bariatric surgery or gastric bypass, your anatomy has changed in ways that often interfere with B12 absorption. Vegans and vegetarians with symptoms of deficiency often benefit from injections, especially if they’ve been avoiding animal products for years.
Hypothyroidism and Vitamin Deficiencies: A Deeper Dive
Hypothyroidism is an endocrine disorder in which the thyroid gland releases low levels of hormones. The condition affects the human body in several ways by affecting bone health, metabolism, etc. Individuals with low vitamin levels in their bodies may develop an autoimmune disease named Hashimoto’s thyroiditis that increases the risks of hypothyroidism.
Causes and Symptoms of Hypothyroidism
Hypothyroidism is mainly caused by autoimmune conditions like Hashimoto’s thyroiditis. In this disease, the thyroid gland of a person is attacked by the immune system, causing low hormone production.
Apart from this, several other factors like iodine deficiency, removal of the thyroid gland through surgery, radiation therapy, certain medicines, etc. also cause hypothyroidism.
The symptoms of hypothyroidism may be present in individuals experiencing the following:
- Cold sensitivity
- Weight gain
- Skin dryness
- Thin and dry hair
- Fatigue
- Constipation
- Depression
- Memory loss
Vitamin D and B12 Deficiency: Causes and Symptoms
A person’s body may lack the required amount of vitamin D due to several factors. A deficiency of vitamin D shows some specific signs and symptoms that help one identify the condition. Several factors lead to vitamin B12 deficiency in the human body including low sources of vitamin B12 in the diet. Knowing the causes and symptoms of vitamin B12 deficiency is essential for timely prognosis.
Relationship Between Hypothyroidism and Vitamin Deficiencies
Hypothyroidism affects the absorption of vitamins in a person's body, causing deficiencies in certain vitamins. Vitamin D is known for its immune-regulating properties. If the immune system fails to function properly due to low levels of vitamin D, it may mistakenly attack the thyroid gland and affect hormone production. Individuals with hypothyroidism have anti-parietal cell antibodies in their body which compromises vitamin B12 absorption. As per records, individuals with hypothyroidism have almost 27% vitamin B12 deficiency.
Diagnosis and Testing
Proper diagnosis and testing procedures can help detect the causes of hypothyroidism at an early stage, leaving enough scope for treatment. Hypothyroidism can be diagnosed through blood tests. Doctors suggest thyroid blood tests to check the levels of thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) in one’s blood. Patients diagnosed with hypothyroidism should opt for routine vitamin D and B12 level tests to keep track of their health conditions.
Treatment and Management
Proper treatment and medication can keep hypothyroidism under control and also normalise the vitamin D and B12 levels in one’s body. The main treatment of hypothyroidism includes adding synthetic hormones to one’s body to replace the thyroid hormone deficiency. The deficiency of vitamin D can be treated with supplements for this vitamin. The treatment for vitamin B12 deficiency depends on the cause of the condition. Doctors may prescribe vitamin B12 oral medicines, nasal gel, nasal spray, or intramuscular injections depending on the patient’s needs.
Dietary Considerations
Apart from medications, one can also intake foods rich in vitamin D and B12 to suffice the deficiency of these nutrients. To normalise hypothyroidism, one can include the following foods in their diet: Selenium-rich foods like Brazil nuts, tuna, turkey. Foods rich in vitamin B12 like cheese, peas, eggs, sesame seeds, beans, etc. For hypothyroidism caused due to iodine deficiency, one should include iodine-rich foods like seafood, seaweed, banana, iodised salts, etc. in their diet.
Lifestyle and Preventive Measures
Regular monitoring of thyroid hormone levels along with vitamin D and B12 status is crucial for effective hypothyroidism management. Besides medications and tests, one can engage in regular physical activities to improve overall well-being. Sunlight is a great source of vitamin D. Thus, moderate sun exposure helps maintain adequate levels of this micronutrient.one can make significant lifestyle changes through stress management techniques such as yoga, meditation, adequate sleep hygiene, and a balanced diet to manage symptoms associated with hypothyroidism.