Vitamins B Complex Deficiency: Causes And Symptoms

What is Vitamin B Complex?

The Vitamin B complex refers to a group of eight essential water-soluble vitamins that support numerous bodily functions. These vitamins include:

• B1 (Thiamine)
• B2 (Riboflavin)
• B3 (Niacin)
• B5 (Pantothenic acid)
• B6 (Pyridoxine)
• B7 (Biotin)
• B9 (Folate)
• B12 (Cobalamin)

Together, they help:

• Convert food into energy (metabolism)
• Maintain healthy skin, brain, and nerve function
• Support red blood cell production
• Keep the immune and digestive systems functioning properly

Since the body does not store large amounts of these vitamins (except B12), a consistent dietary intake is vital to prevent deficiency.

What is Vitamin B complex deficiency?

A Vitamin B complex deficiency occurs when one or more of the B vitamins are insufficient in the body. This can result from poor dietary intake, malabsorption, or increased needs due to health conditions or medications.

For example, Vitamin B12 deficiency may occur if the body cannot absorb it properly, which can impact DNA synthesis and red blood cell production. A deficiency in certain B vitamins can also raise homocysteine levels, increasing the risk of inflammation, cardiovascular disease, and cognitive decline.

Vitamin B Complex Deficiency Causes

A non-balanced diet, excessive alcohol intake,  different medications (such as proton-pump inhibitors, or PPIs), and gastrointestinal malabsorption ailments are a few of the most common causes of vitamin B complex deficiency. So, here are we included some of the causes.

1. Imbalance diet

B vitamins are primarily obtained from food. Diets lacking variety—especially those low in animal products—may result in deficiency.

Vegans and vegetarians are at a higher risk for B12 deficiency, as this vitamin is mostly found in meat, dairy, and eggs.

Diets high in processed food but low in whole grains, fruits, and vegetables may lack other essential B vitamins.

2. Consumption of Alcohol

Alcohol impairs vitamin B absorption and increases excretion through the kidneys, especially thiamine (B1) and folate (B9). Chronic alcohol intake may deplete the body’s vitamin B stores. 

3. Gut Malabsorption

Vitamins B complex is absorbed into the bloodstream by the digestive tract in healthy conditions. The bloodstream carries these vital vitamins throughout your body. If vitamin B isn’t absorbed into the body then it can’t be utilised by the body.

Conditions such as:

• Coeliac disease
• Crohn’s disease
• Ulcerative colitis

may impair the absorption of B vitamins from food, leading to deficiency.  These conditions prevent Vitamin B from entering the bloodstream, resulting in a significant drop in vitamin B levels in your blood and causing harm to your health.

4. Having medications

Long-term use of some medications may interfere with vitamin B absorption or utilisation. These include:

• Metformin (risk of B12 deficiency)
• Proton pump inhibitors (PPIs)
• Anticonvulsants (e.g., phenytoin)
• Methotrexate
• Sulfasalazine
• Isoniazid and hydralazine

If you’re on these medications, regular monitoring and possible supplementation may be necessary.

Also Read: Top 10 Vitamin B5 Foods

Vitamin B Complex Types and Symptoms of Deficiency

1. Thiamine Deficiency (B1)

Thiamine keeps the nervous system healthy by turning food into energy. The body can’t make thiamine on its own. But most of the time, you can get everything you need from the food you eat.

Thiamine deficiency symptoms include:

• Appetite and weight loss

• Confusion or memory issues
• Problems with the heart
• Muscle mass deterioration
• Reaction times are slow.

2. Deficiency of riboflavin (B2)

The deficiency of riboflavin is uncommon. But it can occur when a person has an endocrine disorder, such as thyroid problems, or other illnesses.

Riboflavin deficiency symptoms:

• Disorders of the skin
• Sores around the mouth’s corners
• Mouth and throat swelling
• Swollen or cracked lips
• Hair loss
• Red, itchy eyes
• Anaemia and cataracts can result from a severe riboflavin deficiency

3. B3 (Niacin)

Vitamin B3 helps in digestion and a healthy appetite, as well as for cell development.

Niacin deficiency can lead to digestive problems like nausea and abdominal cramps. Mental confusion can also be caused by a severe deficiency of niacin.

Pellagra is a condition caused by severe deficiency, and symptoms include:

• A bright red tongue
• Vomiting
• Aggressive
• Paranoid
• Suicidal behaviour
• Constipationor diarrhoea
• Fatigue

4. B5 (Pantothenic Acid)

Pantothenic acid is required for the production of new coenzymes, proteins, and fats by the body. Red blood cells transport pantothenic acid throughout the body, allowing it to be used in a diverse group of energy and metabolism processes.

Deficiency of pantothenic acid causes symptoms, such as:

• Hands and feet numbness and burning sensations
• Irritability
• Anxiety
• Poor sleep
• Lack of appetite

5. B6 (Pyridoxine)

Vitamin B6 known as pyridoxine supports the immune system, which helps defend the body from infections.

Vitamin B6 deficiency symptoms include:

• Anaemia
• Depression
• Confusion
• Nausea
• Infection susceptibility
• Dermatitis(skin rashes)

6. B7 (Biotin)

Biotin is energy providing vitamin, and it is found in hairs, skin, and nails. Some people believe that biotin can aid in the treatment of psoriasis. Biotin is required by the human body for a variety of functions, including fat, carbohydrate, and protein breakdown, cell communication, and DNA function.

Biotin deficiency symptoms:

• Hair loss
•  A scaly rash develops around the eyes, nose, and mouth,
• Brittle nails
• Hallucinations
• Depression
• Fatigue

7. B9 (Folate)

Folate (vitamin B9) is present in a wide range of foods. Vitamin B9 promotes the development of red blood cells. When consumed by pregnant women, it also lowers the risk of birth defects.

Vitamin B9 deficiency symptoms:

• Weakness
• Fatigue
• Irritability and difficulty concentrating
• Headache
• Palpitations in the heart
• Breathing problems
• Mouth sores
• Colour changes in the skin, hair, or fingernails

8. B12 (Cyanocobalamin)

Vitamin B12, known as cyanocobalamin, helps  regulate the nervous system. It also helps in the formation of red blood cells and growth. A vitamin B12 deficiency can cause problems with the nervous and circulatory systems.

Vitamin B12 deficiency causes megaloblastic anaemia, which is a condition in which the bone marrow produces large, shaped red blood cells that do not function properly.

Deficiency of vitamin B12 causes symptoms, like:

• Fatigue or Exhaustion
• Weakness
• Loss of appetite
• Slimming down
• Numbness and tingling in the hands and feet
• Confusion
• Lack of memory
• Sore mouth or tongue

Sources of vitamin B

Vitamin B is found in a variety of foods, making it simple to get enough through your diet. Vitamin B should be obtained from a variety of food sources. This will ensure that you get enough of each type.

Vitamin B Food List:

• Milk
• Cheese
• Eggs
• Liver and kidney
• Meat- chicken and red meat
• Fish- tuna, mackerel, and salmon
• Shellfish- oysters and clams
• Dark green vegetables- spinach and kale
• Vegetables- beets, avocados, and potatoes
• Whole grains and cereals
• Kidney beans, black beans, and chickpeas are examples of beans.
• Nuts and seeds
• Fruits- citrus, banana, and watermelon
• Soy milk and tempeh are examples of soy products.
• Blackstrap molasses
• Wheat germ
• Yeast and nutritional yeast

Takeaway Message

Vitamin B complex plays an integral role in maintaining energy levels, brain health, immune function, and red blood cell formation. Deficiency in one or more B vitamins may lead to a wide range of symptoms—from fatigue and skin issues to neurological complications.

Certain groups—such as vegetarians, individuals with digestive disorders, heavy alcohol users, and those on specific medications—are at higher risk. A varied, nutrient-rich diet is the best defence against deficiency. However, supplementation may be necessary in certain cases.

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References:

• Ankar, A., & Kumar, A. (2024, September 10). Vitamin B12 deficiency. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK441923
• Herrmann, W., & Obeid, R. (2008). Causes and early diagnosis of vitamin B12 deficiency. Deutsches Ärzteblatt International. https://doi.org/10.3238/arztebl.2008.0680
• Shipton, M. J., & Thachil, J. (2015). Vitamin B12 Deficiency – A 21st Century Perspective . Clinical Medicine (London, England), 15(2), 145–150. https://doi.org/10.7861/clinmedicine.15-2-145
• Langan, R. C., & Goodbred, A. J. (2017). Vitamin B12 Deficiency: Recognition and Management. American Family Physician, 96(6), 384–389. https://www.aafp.org/pubs/afp/issues/2017/0915/p384.html