M.D. Medical Director, Psychiatrist
When vitamin B-12 levels are low, people may experience fatigue, brain fog, mood changes, and symptoms that closely resemble depression. But what is the connection between vitamin B-12 and depression exactly?
In this blog post, we’ll share what you need to know about vitamin B-12, including its role in the body, what causes deficiency, how to know if you’re deficient in B-12, and the connection between vitamin B-12 and depression.
What is a vitamin B-12 deficiency?
Vitamin B-12 plays an essential role in the body’s overall well-being, from producing red blood cells to supporting nerve function and brain health. When the body doesn’t get enough of this essential nutrient, it can lead to a vitamin B-12 deficiency. This in turn can cause a range of neurological and psychiatric problems – including, in some cases, changes in mood or energy levels.
Vitamin deficiencies occur when the body either isn’t getting enough of a vitamin through food or isn’t absorbing it properly. When it comes to B-12, both of these scenarios are common:
- Dietary causes: Vitamin B-12 is found naturally in animal-based foods like meat, dairy, eggs, and fish. This means people who follow a vegan or vegetarian diet can be more likely to experience a deficiency, especially if they don’t eat fortified foods or take supplements.
- Absorption issues: Some people consume enough B-12 but still develop a deficiency because their body can’t absorb it effectively. This could be due to certain medical conditions (like pernicious anemia or gastrointestinal disorders), mediations, or age-related changes in digestion.
If left untreated, low vitamin B-12 levels can impact a person’s energy levels, concentration, memory, and mood. Some research has even explored a possible link between B-12 deficiency and depressive symptoms, which we’ll explore further in later sections.
See: How Diet and Exercise Affect Your Mental Health
Sources of vitamin B-12
Common sources of B-12 include:
- Animal-based foods: Including beef, liver, poultry (chicken, turkey), eggs (especially yolks), dairy products (milk, cheese, yogurt), fish, and shellfish.
- Fortified foods: Such as breakfast cereals, plant-based milks (soy, almond, oat), nutritional yeast, fortified tofu, meat alternatives (veggie burgers, tempeh), and some energy bars or drinks.
- Supplements: Available as oral tablets, multivitamins, or prescription options.
The role of B vitamins in the nervous system
B-12, also known as cobalamin, is just one of the B vitamins, which also include B1 (thiamine) and B5 (pyridoxine). These vitamins play a central role in keeping the brain and nervous system functioning properly, supporting everything from energy production and nerve protection to the regulation of mood and cognition.
The effects of B vitamins are especially important in the parasympathetic nervous system, the part of the body responsible for rest, repair, and recovery. When B vitamins are low, the nervous system can struggle to regulate itself, which can impact mental clarity, emotional balance, and physical energy.
Vitamins B1 and B6
Vitamin B1 supports the conversion of carbohydrates into energy. This helps fuel cells, including brain cells. It also acts as an antioxidant that helps protect nerves from damage caused by oxidative stress, which is associated with aging and chronic disease.
Vitamin B6 is essential for the creation of neurotransmitters, the chemical messengers that regulate mood, sleep, and cognition. It also helps modulate GABA, a calming neurotransmitter that prevents overstimulation in the brain. Balanced GABA activity is important for emotional regulation and preventing symptoms like anxiety and agitation.
Vitamin B-12
Vitamin B-12 plays two especially vital roles in the nervous system.
Firstly, it helps form the myelin sheath, which is a protective layer that surrounds nerve fibres (called axons). This sheath acts like insulation that allows electrical signals to travel efficiently between the brain and body. Proper myelination is essential for fast, accurate communication between different regions of the brain, supporting everything from muscle coordination to memory and focus.
When B-12 is low, myelin breaks down. This leads to slower signal transmission and a higher risk of nerve damage. Over time, this can affect both physical and cognitive functioning.
Vitamin B-12 also plays a role in the synthesis of neurotransmitters. It helps convert raw chemical compounds into the messengers that regulate how we think, feel, and respond to the world. Without enough B-12, the brain might not produce adequate levels of these vital messengers, which can potentially lead to mood changes, fatigue, and even depression symptoms.
Read More: Parent’s Guide to Helping Teens With Depression
The connection between vitamin B-12 and depression
We have always recognized that vitamin B-12 is essential for brain health, but its exact role in mood regulation and depression is still being studied. Although the connection between the two isn’t yet fully understood, research suggests that low levels of B-12 may be linked to an increased risk of depression, and that maintaining adequate levels could support better treatment outcomes.
In 2005, a review published in the Journal of Psychopharmacology found significant evidence that low serum levels of vitamin B-12 were associated with higher rates of depression. The researchers also noted that people with higher B-12 levels tended to respond better to depression treatment. They suggested that a daily B-12 vitamin supplement of 1 milligram (1,000 mcg) might benefit people experiencing depressive symptoms, although more research is needed to confirm the optimal dosage and effect.
One possible explanation for this lies in B-12’s role in supporting the production of serotonin and other brain chemicals involved in mood regulation. While serotonin’s exact role in depression is still being debated, low serotonin levels have traditionally been linked to symptoms such as sadness, low energy, and irritability – all of which are often seen in people with major depressive disorder.
In another longitudinal study focused on adults aged 50+, those with low B-12 levels were found to have a 51% higher risk of developing depression over a four-year period. Given that one in eight older adults is estimated to have low B-12, this connection is especially relevant for aging populations. In a randomized controlled study, daily supplementation of vitamin B-12 and folic acid was found to increase cognitive function.
What are some B-12 deficiency symptoms?
Signs of low vitamin B-12 can often mimic depressive symptoms, such as fatigue or poor concentration. However, B-12 deficiency can also cause unique symptoms that aren’t often seen in depression alone.
Here’s a quick comparison of B-12 deficiency symptoms vs depressive symptoms:
| SYMPTOM | DEPRESSION | B-12 DEFICIENCY |
| Exhaustion / Fatigue | ✓ | ✓ |
| Rapid heartbeat without exercising | ✓ | |
| Brain fog / Difficulty concentrating | ✓ | ✓ |
| Confusion / Impaired thinking | ✓ | |
| Physical weakness | ✓ | |
| Dizziness / Lightheadedness | ✓ | |
| Trouble sleeping | ✓ | |
| Loss of interest in activities | ✓ | |
| Forgetfulness | ✓ | |
| Changes in appetite | ✓ | |
| Feelings of guilt or anger | ✓ |
Can B-12 help with depression?
While taking vitamin B-12 can support overall brain function and mood stability, research shows mixed results when it comes to whether B-12 alone can prevent or relieve depression. It may be helpful to take dietary supplements as part of a broader treatment plan, especially if you are deficient in B-12, but they shouldn’t be taken as a replacement for therapy, medication, or other evidence-based treatments.
If you’re struggling with depression, it’s best to speak with a mental health professional who can evaluate your symptoms, recommend lab testing if needed, and create a personalized treatment plan that fits your needs.
Risk factors for vitamin B-12 deficiency
Knowing the risk factors for vitamin B12 deficiency can help you identify when supplementation or testing might be necessary, especially if you’re feeling symptoms like fatigue, low mood, or brain fog.
Common risk factors for B-12 deficiency include:
1. Plant-based diets
Vitamin B-12 is found almost exclusively in animal products like meat, poultry, dairy, fish, and eggs. People who follow vegetarian or vegan diets might not get enough B-12 through food alone and are at a higher risk of developing deficiency over time. You can prevent this by eating more fortified foods (e.g. cereals or plant-based milks) or taking a daily B-12 supplement.
2. Digestive conditions
Some medical conditions can interfere with the body’s ability to absorb B-12 from food. These include Crohn’s disease, celiac disease, or atrophic gastritis (chronic inflammation of the stomach lining). These conditions can lead to long-term B-12 deficiency if not managed properly.
3. Weight loss surgery
Surgeries that alter the stomach or intestines, like gastric bypass, can impact the body’s ability to extract B-12 from food. People who undergo these procedures often require lifelong B-12 supplementation.
4. Age over 50
As we age, our stomach naturally produces less acid, which is needed to separate B-12 from the proteins in food. This can lead to reduced absorption, even if you have an otherwise normal diet. Older adults are often encouraged to get B-12 from supplements or fortified foods to prevent deficiency.
5. Using certain medications
Some commonly prescribed medications can affect how the body absorbs B-12. These include proton pump inhibitors and H2 blockers, which are used to treat acid reflux or heartburn, and metformin, a diabetes medication.
6. Inhibited intrinsic factor
Your body needs a protein called intrinsic factor to absorb B-12. Sometimes, particularly for people with an autoimmune condition called pernicious anemia, the immune system attacks the cells that make intrinsic factor. Without it, even a diet that’s high in B-12 won’t be enough, and injections or supplements are needed.
Read More: Persistent Depressive Disorder – Overview, Symptoms and Causes
How is a vitamin B-12 deficiency diagnosed?
If you’re experiencing fatigue, low mood, or brain fog and think you have a vitamin B-12 deficiency, it’s important to speak with your doctor. They can do a simple blood test to check your vitamin levels and determine whether B-12 is playing a role in how you’re feeling.
Before your appointment, you might want to consider:
- Medications and supplements you’re currently taking
- Your symptoms, including when they started and how often they occur
- Questions to ask your doctor.
Most vitamin test results are available in a few days. If your B-12 levels are low, your doctor will help you create a plan to address the deficiency. This could include dietary changes and temporary supplements, depending on your overall health and how severe your deficiency is.
If your test results come back normal, that’s also helpful! It can rule out B-12 as a significant contributing factor and allow your care team to explore other causes of your symptoms, such as depression or another underlying condition.
Treatment options for vitamin B-12 deficiency
If test results confirm a B-12 deficiency, the most effective treatment options are usually adjusting your diet and, if needed, taking supplements under medical supervision.
Dietary changes
If you’re not vegan or vegetarian, consider adding more B-12 foods to your meals, such as egg whites, poultry, lean meats, and fish. You could also start your day with fortified breakfast cereals and plant-based milk.
Supplements
If your B-12 deficiency is more severe, or dietary changes aren’t enough, your doctor might recommend oral B-12 supplements, or in some cases, B-12 injections. These treatments are generally safe but it’s important to speak with your provider before starting any new supplements, especially if you take other medications.
Does a lack of B-12 cause depression?
There’s yet to be a firmly established causation between vitamin B-12 deficiency and depression, but there is growing evidence that low B-12 levels may contribute to depressive symptoms, especially in older adults or those with other risk factors.
Vitamin B-12 plays an important role in many neurochemical processes, including producing neurotransmitters and maintaining myelin sheaths, both of which are critical for healthy brain function. Low B-12 levels can disrupt these symptoms and potentially lead to mood changes and cognitive difficulties.
What are some depressive and cognitive symptoms related to B-12 deficiency?
Some cognitive and emotional symptoms related to vitamin B-12 deficiency include:
- Fatigue: Without enough B-12, red blood cell production drops, reducing the delivery of oxygen to the brain and body. This leads to physical and mental exhaustion.
- Brain fog and memory issues: B-12 deficiency can damage the microstructure of the hippocampus, a brain region essential for memory and learning.
- Irritability: B-12 helps break down homocysteine, a byproduct of metabolism. High homocysteine levels are linked to low B-12 and associated with mood disturbances.
- Cognitive decline: Low B-12 is associated with increased risk for Alzheimer’s disease, brain shrinkage, and general cognitive impairment – especially for older adults.
Similar Reading: The Link Between Depression and Chronic Pain
Summary: Vitamin B-12 and depression
While vitamin B-12 deficiency might not directly cause depression, research suggests it can contribute to similar symptoms like fatigue, irritability, brain fog, and low mood. Increasing your B-12 levels can be part of a depression treatment journey, but it should always be combined with evidence-based care like therapy, medication, and treatments like TMS.
If you’re seeking a depression diagnosis or exploring treatment options, our team at BestMind Behavioral Health is here to help. Take our Depression Self-Assessment and one of our team members will reach out, or contact us directly to schedule a consultation today.
