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The Vitamin B12 Connection

Overall health is the result of many different factors. Diet, lifestyle, genetics, and the environment all contribute to the state of well-being. Although it is difficult to distinguish the impact of any one aspect that influences health, vitamin B12 has proven a vital link.

Vitamin B12 is one of the thirteen essential vitamins that the body needs in order to stay alive. It is considered unique in that it is the only one of the essential vitamins that contain the trace mineral cobalt. Hence, B12 is sometimes referred to by its scientific name cobalamin.

Another characteristic that sets vitamin B12 apart is its natural source. B12 is produced only in the gut of animals so, unlike other vitamins, we can’t obtain it from plants or from sunlight. The best dietary sources of vitamin B12 include:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Shellfish
  • Milk and most other dairy products

In Could It Be B12?, co-authors Sally Pacholok, RN, and Jeffrey Stuart, DO, state that many people associate a vitamin B12 deficiency with vegetarians or vegans who don’t eat foods containing B12, but the majority of those with a deficiency eat plentiful amounts of foods containing B12; they simply are unable to absorb or effectively make use of vitamin B12 in their bodies.

B12’s Many Functions

Vitamin B12 is necessary for the proper functioning of many basic systems in the body. It is crucial for sustaining physical, emotional and mental energy. B12 is essential for female reproductive health and pregnancy. It affects everything from cell formation to circulation to moods.

Digestion and Metabolism

Vitamin B12 plays an important role in converting food to energy. It affects digestion, nutrient absorption, and metabolism. Ironically, those who are already low in vitamin B12 have more difficulty absorbing it and getting it into the bloodstream to make it available to the body. Without intervention, this creates a vicious cycle of deficiency.

Nervous System

Vitamin B12 helps in the production of the soft, fatty material called myelin that surrounds and protects nerve fibers. A deficiency in B12 can compromise the myelin and can result in serious neurological problems. Vitamin B12 deficiencies have, in some cases, been misdiagnosed as multiple sclerosis (MS).

Immune System

Vitamin B12 also plays a critical role in the production of white blood cells, which are key components in the immune system. Vitamin B12 deficiency has been shown to lead to reduced numbers of white blood cells, which may increase susceptibility to infections and diseases.

Blood Supply

Red blood cells carry oxygen from the lungs to the brain and other organs and tissues. Without an adequate supply of B12, red blood cells become abnormally large and are destroyed more rapidly. Fewer functioning red blood cells are then available to circulate throughout the body and carry oxygen. This condition, called anemia, causes the body to feel exhausted and weak.

If anemia continues untreated, it can lead to serious health problems, including nerve damage and an increased risk for stroke. In a report titled Vitamin B12: Essential for Vigorous Good Health, Dr. Joseph Mercola states that chronic anemia can affect “everything from your balance to your sense of smell.”


Vitamin B12—along with vitamin B6, folate, and other nutrients—are involved in the process of methylation whereby small parts of molecules, called methyl groups, are transferred to other molecules such as hormones, proteins, and DNA.

The liver uses methylation to detoxify substances. If there are not enough nutrients to supply an adequate number of methyl groups, levels of homocysteine (an amino acid in the body) build up in the blood and urine.

Elevated homocysteine levels are associated with hormone imbalance. Efficient methylation is crucial for metabolizing the estrogen hormones; it is the pathway for eliminating excess estrogen from the body. Failure to provide enough methyl groups leads to elevated homocysteine levels and allows estrogens to accumulate, resulting in hormone imbalance. Elevated homocysteine levels have also been associated with an increased risk of heart disease.

Common Causes of Vitamin B12 Deficiency

Medications Antacids, antibiotics, birth control pills, and many other medications may interfere with the body’s ability to absorb or use of vitamin B12.
Gastritis This condition causes inflammation and deterioration of the stomach lining, resulting in reduced stomach acid secretion, which is needed to free B12 from animal protein.
Gastric bypass Individuals who have undergone this procedure are at risk for vitamin B12 deficiency because they lose the cells in their stomach that produce acid.
Digestive disorders Bacterial overgrowth in the small intestine or parasitic infections can affect the normal metabolism of vitamin B12.
Crohn’s disease Along with other GI disorders such as enteritis or celiac disease, this can interfere with B12 absorption.
Dietary deficiencies Lack of meat, eggs, or dairy products (all primary sources of B12) may result in B12 deficiency.

B12 Deficiency

Growing evidence supports the importance of B12 with regard to hormone balance, in that many of the disorders associated with a hormone imbalance are also associated with a vitamin B12 deficiency. Without adequate B12, overall health is compromised in fundamental ways.

One of the reasons people become deficient in vitamin B12 is that, with age, the digestive system gradually loses its ability to produce hydrochloric acid, which is necessary for releasing vitamin B12 from food. Dr. Mercola suggests that “If you’re over 50, it’s safe to assume you are not absorbing vitamin B12 at an optimal level.”

Symptoms of a vitamin B12 deficiency include:

  • Unexplained fatigue or loss of energy
  • Muscle weakness
  • Poor circulation
  • Tingling in the extremities
  • Apathy
  • Lack of motivation
  • Mental fogginess
  • Memory problems
  • Unusual mood swings

While working as an emergency department nurse, Ms. Pacholok frequently observes “patients presenting with generalized weakness, anemia, shortness of breath, neuropathy, difficulty ambulating, mental status changes, mental illness, and fall-related trauma” only to find that they are deficient in B12. She suggests that all too often these types of symptoms fall under a diagnosis of “normal aging” or other conditions when vitamin B12 is the real culprit.

Although vitamin B12 is water-soluble, it does not exit the body quickly in urine. When everything is functioning properly, there is nearly a year’s supply stored throughout the body, primarily in the liver. Dr. Mercola warns that “a deficiency may not show itself for a number of years, depending on your diet and your body’s ability to efficiently absorb B12. This time lag is a serious concern because after about seven years of B12 deficiency, irreversible brain damage can result.”

Dementia and Alzheimer’s Disease

A vitamin B12 deficiency can seriously impair proper functioning of the nervous system, affecting an individual’s mental state, and leading to memory loss, fuzzy thinking, personality changes, and erratic moods. These symptoms all appear as classic dementia when it just might be a vitamin B12 deficiency.

Fortunately, there is growing recognition of the link between vitamin B12, dementia, and Alzheimer’s disease. Joseph G. Hattersley, MA, proposes that an early launch of high dose vitamin B12 treatment, soon after the first warning symptoms appear, may even turn off the process. And Dr. John V. Dommisse states that “most cases of Alzheimer’s dementia are actually missed B12 deficiency cases.” He believes that approximately 75 percent of the dementia cases brought on by B12 deficiency could be reversed if the condition is discovered early enough.

Researchers conducted a 7-year investigation involving a group of 271 healthy individuals, 65-79 years of age, to explore the relationship among homocysteine levels, vitamin B12 levels, and a diagnosis of Alzheimer’s disease. They found that elevated homocysteine levels were associated with an increased risk of Alzheimer’s disease, while increased B12 decreased the risk of Alzheimer’s disease.

Mental Health

As mentioned earlier, B12 is important to the health of nerve cells in the brain that control moods and behaviors. And, while a vitamin B12 deficiency may not be the direct cause of most cases of mental illness, it is believed to play some role, particularly in cases involving depression. According to Dr. Mercola, depression is believed to be associated with a shortage of monoamine neurotransmitters, which are produced by the central nervous system, with the help of B12.

One type of depression is postpartum depression. Ms. Pacholok and Dr. Stuart note that “Pregnancy can drastically worsen a pre-existing B12 deficiency because B12 is transferred to the growing fetus throughout pregnancy.”

Unfortunately, people of all ages who suffer from severe depression, anxiety, paranoia, and a rash of other psychiatric disorders are prescribed dangerous narcotics or other drugs, when the underlying problem may actually be a vitamin B12 deficiency.


While there are many different causes of female and male infertility, B12 deficiency is one factor that is often overlooked. In some cases, doctors have reported that anovulation (a failure to release an egg during the monthly cycle) occurs in some women with B12 deficiency. In these cases, a cause of the B12 deficiency is the decreased production of intrinsic factor (IF), a protein normally made in the stomach, which is necessary for proper absorption of B12. This leads to the development of malformed red blood cells, known as pernicious anemia.

Some studies have noted a link between B12 deficiency and abnormal estrogen levels that may interfere with the implantation of the fertilized egg. Dr. Michael Bennett describes a connection linking B12 deficiency with not only a failure to get pregnant but also a failure to successfully carry a baby full-term.

A vitamin B12 deficiency has also been associated with abnormalities of the cells of the reproductive tract, extending to the lining of the uterus and cervix, which might be diagnosed as cervical dysplasia. Observation of these abnormalities caused by a B12 deficiency can also be mistaken for a precancerous condition.


The Framingham Osteoporosis study demonstrated a strong link between low levels of vitamin B12 and osteoporosis, characterized by thinning, weakened bones. A follow-up study by Tucker, et al. found that B12 is important to DNA synthesis, thereby affecting bone formation. Another study by van Meurs, et al. examined levels of homocysteine, which increases with low B12, and the likelihood of bone fractures. In both men and women, those with the highest concentration of homocysteine were much more likely to fracture a hip or experience a broken bone.

These studies all suggest that vitamin B12 may benefit bone health, while low levels of B12 can lead to the development of osteoporosis. Ms. Pacholok and Dr. Stuart go on to state that these findings are not surprising as vitamin B12 is crucial to the function of osteoblasts (bone-forming cells). Insufficient levels of B12 may result in decreased amounts of bone-forming cells and thus compromise the strength and durability of bones.

Breast Cancer

DNA, which contains the genetic instructions for each cell, is continually being damaged and therefore needs to be constantly repaired. Because methylation controls both the production and repair of DNA, nutrients that provide methyl groups are linked to the cancer process.

Dr. Martin Lajous led a study that investigated the connection between B12 and breast cancer. The results suggest that a high intake of folate, vitamin B6, and vitamin B12 may lower the risk of breast cancer. Conversely, low levels of folic acid, vitamin B6, and vitamin B12 are associated with increased breast cancer risk.

Vitamin B12 Testing

If you believe that you may have a vitamin B12 deficiency or any of the related health concerns described here, a healthcare professional can administer or request a test to measure your B12 levels. The most common B12 test is a serum test that measures the level of vitamin B12 in your blood serum. According to Ms. Pacholok and Dr. Stuart, experts advise further testing if your level is below 350 picograms/milliliter (pg/ml).

The methyl­malonic acid (MMA) test is more sensitive and specific. This test measures the level of MMA in either urine or blood. The principle behind this test is that vitamin B12 is required to metabolize MMA; in short, an elevated level of MMA indicates decreased B12 activity.

Another way to determine if you are deficient in B12 is to test your homocysteine (Hcy) level. Elevated levels of homocysteine in the blood indicate a B12 deficiency, and possible deficiencies in vitamin B6 or folate as well. Although this test is not necessary to diagnose a B12 deficiency, it is considered a valuable tool, along with either a serum B12 or MMA test.

Vitamin B12 Supplements

Supplemental vitamin B12 is available in three forms—cyanocobalamin, methylcobalamin, and hydroxocobalamin—and can be supplemented orally, nasally, dissolved under the tongue or by injection.

While there is some controversy over which form is most preferred, or considered to be most effective, current evidence suggests that methylcobalamin may be superior to the others, especially in cases involving neurological disease. According to Ms. Pacholok and Dr. Stuart, methylcobalamin is believed to be more effective because it is able to cross the blood-brain barrier, thereby leaving the bloodstream and actually entering into the brain tissue where it is needed.

For most people, there is very little (if any) downside to supplementing vitamin B12, and a lot of downside to living with a B12 deficiency. However, according to, if you are allergic to cobalt (or cobalamin, the other name for B12) or if have a family history of Leber’s disease (a hereditary eye disease), you should avoid injectable vitamin B12 (cyanocobalamin), as it may cause more harm than good in these cases.

For optimal health, it is important to work with your healthcare practitioner to monitor your vitamin B12 levels.

Connections is a publication of Women’s International Pharmacy, which is dedicated to the education and management of PMS, menopause, infertility, postpartum depression, and other hormone-related conditions and therapies.

This publication is distributed with the understanding that it does not constitute medical advice for individual problems. Although this material is intended to be accurate, proper medical advice should be sought from a competent healthcare professional.

Publisher: Constance Kindschi Hegerfeld – Executive VP, Women’s International Pharmacy
Co-Editors: Julie Johnson and Carol Petersen, RPh, CNP – Women’s International Pharmacy
Writer: Kathleen McCormick – McCormick Communications
Illustrator: Amelia Janes – Midwest Educational Graphics

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