Vitamin B Explained: Types, Functions, Sources, Deficiencies

B vitamins are micronutrients that our bodies require to function properly. These eight different vitamins can be found in various foods. When we eat a well-balanced diet, we get the nutrients we need to produce energy, make and repair DNA, and avoid deficiencies. In the U.S., vitamin B deficiencies are uncommon.

Key takeaways:

Still, they can occur in people with underlying GI diseases, alcoholism, genetic abnormalities, improper diets, and food insecurity. It is essential to eat a wide array of foods to maintain an adequate vitamin B supply.

Types of B vitamins

When talking about B vitamins, we are talking about eight individual vitamins, each with their own role in the body.

B vitamin numberVitamin name
B3niacin (nicotinic acid or nicotinamide)
B5pantothenic acid

Vitamins aid in various processes within the body, including assisting in enzyme reactions and supporting our immune system. Some promote digestion, while others help transport oxygen and energy throughout the body.

B vitamins are naturally produced by various organisms, ranging from plants to yeast to bacteria. However, mammals, including humans, cannot make these vitamins. They must be ingested from our diet or bacterial sources, such as those that help support our GI tracts.

Vitamins are either water-soluble (can be dissolved in water) or fat-soluble (can dissolve in oils or fats). B and C vitamins are water-soluble, while vitamins A, D, E, and K are all fat-soluble. Fat-soluble vitamins can be stored in the body, while water-soluble vitamins cannot — they are released into the urine.

Functions of B vitamins

Though the functions of individual B vitamins vary, this group of vitamins collectively plays countless key roles in the body, including but not limited to:

  • Brain function;
  • Energy metabolism;
  • Production and repair of DNA and RNA (genetic building blocks);
  • Help in production of various chemicals the body needs.

Sources of B vitamins

We can obtain B vitamins from various sources. Eating a well-balanced diet is crucial to ensuring one acquires enough vitamin B. No single food source can provide all the B vitamins needed to function normally. Thus, a variety of foods contribute to a properly balanced diet.

Several foods contain more than one B vitamin. So, you can reach for foods with more bang for the buck, such as eggs and cereals (often fortified with B vitamins), to get your daily requirements.

Sources of B vitamins also include the bacteria that naturally reside in our gut. These commensal organisms help support our digestive function and immune system. However, for these organisms to be beneficial, they must be in proper balance. Today, many people have various GI diseases or other imbalances that alter the GI microbiome (gi organisms that reside in our gut and help with digestion). These imbalances increase one’s risk of deficiency unless sufficient amounts are obtained in the diet or via supplementation.

B1 sources

Vitamin B1 can be found in meats (pork and chicken, most notably), beans, rice bran, eggs, cereal sprouts (especially whole grain), liver, green peas, and even pasta. While many foods contain B1, the nutrient can also be obtained from the bacteria that live in our gut.

B2 sources

Dietary sources of riboflavin include liver, eggs, dairy products, legumes (e.g., beans or peas), leafy greens, yeast, salmon, almonds, spinach, fortified foods, and some mushrooms.

B3 sources

Sources of niacin include red meat, poultry, brown rice, legumes, nuts, seeds, bananas, fish, and fortified foods (cereals and breads). Furthermore, various healthy gut bacteria can also produce this vitamin.

B5 sources

Sources of B5 include eggs, chicken, liver or kidney, fortified cereals, broccoli, potatoes, dairy milk, mushrooms, and avocado, to name a few. Bacteria can also produce this vitamin but may compete with a host; therefore, we want to ensure we get sufficient amounts from the diet — enough for our own health and the health of our gut organisms.

B6 sources

Avocado, tofu, poultry, fish, chickpeas, beef liver, bananas, legumes, and sweet potatoes are common sources of B6. Additionally, cereals may be fortified with B6.

B7 sources

Biotin sources (B7) include beans, nuts, and oil seeds. Oil seeds include peanuts, soybeans, sunflowers, sesame, and safflower seeds used to produce various oils and meals that commonly flavor our foods. Liver, cooked eggs, pork, and leafy greens also may provide biotin.

B9 sources

Sources of folate (B9) include asparagus, beef liver, seafood, whole grains, eggs, peanuts, citrus fruits, legumes, and, our friends, green leafy veggies. Furthermore, gut bacteria can also produce this vitamin, which can be directly absorbed by one’s colon and make its way into the bloodstream.

B12 sources

Sources of cobalamin (B12) include eggs, fish, dairy, beef liver, chicken, and seafood. As you can see, all sources of this vitamin come from animals. For vegetarians or vegans, getting sufficient B12 may be problematic. Thus, talk to your healthcare provider if you don’t eat animal products, as you could be deficient in this vitamin.

The good news is that some non-animal foods are fortified with B12. Recognizing that many don’t consume enough animal products to obtain their daily needed cobalamin, foods like nutritional yeasts, tempeh, nori seaweed, some mushrooms, cereals, enriched soy or rice milk, and even tofu can be B12 fortified. These sources may provide B12 required to those who do not consume animal products, or may provide additional supplementation as we age.

B Vitamin Deficiencies

Vitamin deficiencies, including the B group, can increase the risk of developing multiple conditions such as inflammatory, allergy, or infectious diseases.

Vitamin B deficiencies arise worldwide. Sometimes they arise due to food insecurity and a shortage of overall food sources. However, deficiencies occur more and more, especially in developed nations, simply because of a lack of a properly balanced diet.

Thiamin Deficiency (B1)

B1 helps the body obtain energy from food and helps maintain a healthy nervous system. When we lack B1, this can lead to tiredness, weakness, and digestive troubles. Furthermore, there are two conditions caused by insufficient thiamine.

  1. Beriberi disease. It is a specific form of thiamine deficiency that causes damage leading to limb pain and swelling. Additionally, one may demonstrate trouble breathing, abnormal heart rates, or even heart failure.
  2. Wernicke-Korsakoff syndrome. It causes neurological signs, including abnormal walking, eye movements, and memory loss.

Those with obesity and alcohol abuse may be at an increased risk of B1 deficiency.

Riboflavin deficiency (B2)

B2 supports the function of our eyes, nervous system, and skin. It also helps our body obtain energy from food. Readily available in foods, Americans rarely have a B2 deficiency. However, inadequacies may cause weakness, itchy or burning eyes, skin inflammation, pain, burning, or tenderness in the mouth, and anemia (low red blood cell counts). In more severe cases, one may have significant fatigue (lethargy), personality changes, or brain function abnormalities. Those with thyroid disease or nutritional deficiencies may be at a higher risk of low riboflavin levels.

Niacin deficiency (B3)

B3 supports the skin and nervous system while also releasing energy from our foods. Niacin deficiency in industrial nations like the U.S. rarely occurs because it is present in or added to many foods. One of the risk factors for the development of B3 deficiency includes alcohol abuse.

Signs of B3 insufficiency include hair loss, weak muscles, burning in the arms/legs, abnormal gait, and diarrhea. Further symptoms may include headache, depression, dizziness, anxiety, memory problems, aggression, and even paranoia or hallucinations. In rare cases, one may develop Pellagra — a dark scaly rash — when exposed to sunlight.

Low B3 levels are more likely to develop in those who follow restrictive diets, have chronic problems with alcohol, or have cancer.

Pantothenic acid deficiency (B5)

Pantothenic acid functions in various capacities to help the body produce energy. Further, it joins B1 and B2 in controlling different host immune functions.

We can see certain clinical symptoms, such as headache, difficulty sleeping, and exhaustion (fatigue), in persons with low B5 levels. However, this condition is uncommon in the U.S. unless one has a genetic mutation or GI disorder that causes poor nutritional absorption. Further signs may include muscle cramps, numbness, or a burning feeling in the limbs, skin infection or inflammation, and GI signs such as vomiting or nausea.

Pyridoxine deficiency (B6)

This vitamin is involved in over 150 crucial biochemical reactions in the body. So deficiencies will vary with each individual. Pyridoxine plays key roles in the metabolism of amino acids (protein building blocks), carbohydrates, and fats. Additionally, it helps the body to produce hemoglobin. This molecule exists in our red blood cells. It carries oxygen, the key to breathing and other various metabolic processes, throughout the body.

Deficiencies of pyridoxine (B6) may manifest as allergies and rheumatoid arthritis (immune-related diseases), as well as neurological problems. Those lacking B6 (aka pyridoxine, pyridoxamine, or pyridoxal) may show anemia, irritability, abnormal mentation, dementia, depression, and even seizures.

B6 deficiency risks include alcoholism, lack of ability to absorb B6 as we age, and kidney disease. Those with immune-mediated diseases like Crohn’s disease or rheumatoid arthritis, and even those who take birth control medications, are also at risk.

Biotin deficiency (B7)

Biotin is essential for proper amino acid, fatty acid, and glucose (sugar) metabolism.

Though rare in the U.S., signs of deficiency may include an oily, scaly rash, burning of the extremities, depression, tiredness, seizures, or hallucinations. Those with type II diabetes and other conditions that cause poor glucose balance are at a higher risk for this deficiency.

Folate deficiency (B9)

Folate plays a role in making DNA and helping to synthesize amino acids. Our red blood cells also require high levels of this vitamin, so maintaining high levels is key to supporting various roles in our bodies.

Many are familiar with folate since it is a well-known vitamin needed for fetal health (reproduction and baby development). Supplementation as part of a neonatal vitamin is key in neonatal health because it helps prevent brain and spinal cord abnormalities during development. Supplementation with folic acid (the synthetic form of B9) should ideally be started several months before pregnancy. This helps to ensure a baby’s healthy development, as many women often do not get enough B9 from food.

Generally, problems with B9 may include anemia, spinal cord issues, and various metabolic problems. Additionally, weakness, sleepiness, abnormal heartbeat, shortness of breath, and sores in the mouth may occur. Finally, neurologic changes such as dementia, behavioral changes, and cognitive decline may arise.

In addition to known issues with pregnancy, low B2 and B12 levels can predispose to B9 deficiencies. GI disorders such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and others that cause improper nutrient absorption can also lead to a deficiency. However, folate deficiency generally remains rare in the U.S. since it is readily available in many foods.

Cobalamin deficiency (B12)

B12 assists in red blood cell production and helps maintain a happy, healthy nervous system. Like many other B vitamins, it helps release energy from food and helps the body use folate.

Cobalamin deficiency may manifest in anemia and problems with the nerves, including numbness in the feet and hands. Further signs may include neurologic changes such as mental deterioration or behavioral changes.

Risk factors for B12 deficiency include decreased nutrient absorption, vegetarianism, and veganism. Those with underlying GI conditions such as gastroesophageal reflux disease (GERD), IBS, or IBD may also be at a higher risk. Moreover, those taking medications that block stomach acid production, such as famotidine, omeprazole, or other antacids, may have more trouble absorbing this vitamin.

Do you get enough B vitamins?

As you can see, B vitamins play critical roles in our bodies and are nutrients we cannot do without. A variety of food sources can provide the vitamins we need to maintain proper balance. Failing to eat a properly balanced diet can easily lead to deficiencies and many medical problems.

If you feel your diet is lacking in B vitamins, talk with a medical professional to see if you need supplementation and, if so, what form is best for you. Not all supplements are created equal. But be mindful; eat your greens and foods rich in B vitamins to ensure a healthy life.

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