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Vitamin B12 deficiency and how it can impact your health

Vitamin B12 deficiency and how it can impact your health

Vitamin B12 deficiency and how it can impact your health

There are many different types of B vitamins that each have their own role in how your body functions. Vitamin B12 deficiency, commonly underdiagnosed by conventional medicine, is an increasingly common deficiency across a broad spectrum of our population.

This deficiency has been estimated to affect about 40 percent of people over 60 years of age and may contribute to at least some of the symptoms we attribute to “normal” aging—such as memory loss, cognitive decline and decreased mobility. [1]

Vitamin B12 deficiency can affect almost every system and tissue in the body and is one of the most common reasons that people suffer from fatigue. It plays a vital role in the nervous system, DNA synthesis, detoxification and the synthesis of hormones and neurotransmitters.

The good news is that Vitamin B12 is nontoxic and water-soluble so it’s easy to replace.

How can you ensure you are getting enough Vitamin B12? And how do you find out if you have a deficiency? Read on to find out more.

What is Vitamin B12 and how do we absorb it?

Vitamin B12 is a water-soluble vitamin. Because vitamin B12 contains the mineral cobalt, compounds with vitamin B12 activity are collectively called “cobalamins”. Cobalamin is stored in the liver, kidney, heart, spleen, and brain.

It is naturally present in animal foods, added to others and available as a dietary supplement and a prescription medication.

Vitamin B12 binds to the protein in the foods we eat. The process starts in the mouth when food is mixed with saliva. The freed vitamin B12 then binds with haptocorrin, a cobalamin-binding protein in the saliva. In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine. [2]

In this way, no more than about 2 μg of vitamin B12 can be ingested per meal. Therefore, when getting B12 from food, people rely on taking B12 several times a day, in order to meet their total requirement.

This means that it doesn’t really matter is you eat a meal that contains a food very rich in B12, such as clams or offal, or if you eat a meal with a food with lower concentration of B12 sources. There is a limited amount of the vitamin that can be absorbed.

The body can store vitamin B12 for up to four years and it can get rid of any excess or unwanted vitamin B12 in the urine.

Why do you need Vitamin B12?

The workings of B12 can be divided into five key areas:

  • Synthesis of DNA – the vitamin influences cell division and blood formation
  • Energy metabolism – B12 is vital for energy production in the mitochondria
  • Lipid metabolism – vitamin B12 is important for the building and maintenance of the cell membrane and myelin sheaths, a protector of the nerves in the central nervous system and brain
  • Synthesis of hormones and neurotransmitters – the vitamin is needed to produce crucial neurotransmitters and therefore influences mood, psyche and perceptions
  • Detoxification – homocysteine and cyanide are neutralised by B12, as well as radicals such as nitric oxide and peroxynitrite. The vitamin is an important opponent to nitrosative stress [3]

Methylcobalamin (functions in the cell plasma as a coenzyme in the methylation cycle) and 5-deoxyadenosylcobalamin (functions in the mitochondria as a coenzyme in the citric acid cycle) are the metabolically active forms of vitamin B12. However, two others forms, hydroxycobalamin and cyanocobalamin, become biologically active after they are converted to methylcobalamin or 5-deoxyadenosylcobalamin.

Vitamin B12 and folate play important roles in DNA methylation since these two coenzymes are required for the synthesis of methionine and S-adenosyl methionine, the common methyl donor required for the maintenance of methylation patterns in DNA. [4]

Find out more about methylation here.

B12 helps protect the heart by removing a dangerous protein from your blood called homocysteine. If homocysteine levels are too high, it can damage your arteries leading to inflammation and heart disease.

How much Vitamin B12 do you need?

Conventional medicine states that the Recommended Dietary Allowance of Vitamin B12 for men and women ages 14 years and older is 2.4 micrograms daily. For pregnancy and lactation, the amount increases to 2.6 mcg and 2.8 mcg daily, respectively.

Unfortunately, the benchmarks for what classifies as enough Vitamin B12 puts the levels too low so patients may find their doctor tells them their levels are fine but in fact, they need to be higher. Many Functional Medicine health practitioners feel that the lower limit of ‘normal’ should be raised so that those individuals who are displaying B12 deficiency symptoms can be treated.  At Advanced Functional Medicine, we use our own optimal ranges for nutrients such as B12 and screen all patients for this.

What are good sources of Vitamin B12?

Food sources include:

  • Fish, shellfish
  • Liver
  • Red meat
  • Eggs
  • Poultry
  • Dairy products such as milk, cheese, and yogurt
  • Fortified nutritional yeast
  • Fortified breakfast cereals
  • Enriched soy or rice milk

What causes Vitamin B12 deficiency?

The main causes of a deficiency include inadequate dietary intake and malabsorption issues.

There are a few groups who may be prone to developing a Vitamin B deficiency:

  • Vegetarians and vegans are at a high risk for deficiency since their diet largely consists of plant-based foods rather than animal products that tend to be full of B12. Even if a vegetarian or vegan diet is carefully planned, it is difficult to get enough vitamin B12 through plant foods alone.
  • Older adults can tend to absorb less B12.
  • Autoimmune conditions such as lupus or Grave’s disease are also a risk factor for vitamin B12 deficiency.
  • People with conditions that affect the small bowel, including Crohn’s disease, Celiac disease (11-41% of patients with celiac will have B12 deficiency), Small intestinal bacterial overgrowth (SIBO), parasite infections, such as giardia, tapeworm, chronic pancreatitis, and advanced liver disease. [5]
  • People who have a damaged gut lining as a result of diets high in inflammatory foods, chronic stress, and food intolerances, such as to gluten. It’s difficult for nutrients such as B12 to pass through an inflamed and damaged gut lining into the bloodstream. [6]
  • Long-term use of medications, including heartburn pills and oral contraceptives, may also affect levels. [7]
  • Exposure to nitrous oxide
  • Alcohol use
  • Intestinal dysbiosis
  • Leaky gut and gut inflammation
  • Atrophic gastritis or hypochlorhydria, or low stomach acid
  • Pernicious anaemia—a type of megaloblastic, autoimmune anaemia caused by a lack of intrinsic factor (a protein in the stomach that allows the body to absorb vitamin B12) so that vitamin B12 is not absorbed.

What are the signs of Vitamin B12 deficiency?

Symptoms of Vitamin B deficiency may include:

  • Megaloblastic anaemia—a condition of larger than normal sized red blood cells and a smaller than normal amount; this occurs because there is not enough vitamin B12 in the diet or poor absorption
  • Pernicious anaemia—a type of megaloblastic, autoimmune anaemia caused by a lack of intrinsic factor (a protein in the stomach that allows the body to absorb vitamin B12) so that vitamin B12 is not absorbed [8]
  • Fatigue, weakness, low energy
  • Frequent bleeding or bruising
  • Shortness of breath
  • Nerve damage with numbness, tingling in the hands and legs
  • Memory loss, confusion
  • Digestive issues
  • Heart palpitations
  • Dementia
  • Depression
  • Seizures
  • Toxicity

How do you measure Vitamin B12?

Measuring vitamin B12 in the blood is actually not the best way to determine whether someone is deficient, as some people with a deficiency can show normal B12 blood levels. Blood levels of methylmalonic acid, a protein breakdown product, and homocysteine are better markers that capture actual vitamin B12 activity. These values increase with a vitamin B12 deficiency. [9]

A functional medicine doctor will test your blood for B12, homocysteine, and complete blood counts to determine whether you have a deficiency.

You may also need a MTHFR genetic test. “The more mutations one has to this gene, the more they require B12, folate, and B6 for their detoxification pathways and body to function optimally. Other genes are involved with B12 also including the MTRR gene.  It’s estimated that those with one mutation decrease their ability to methylate by 30% and those with two mutations decrease their ability to methylate by 50-70%, making it virtually impossible get adequate B12 from diet alone.” [10]

How do you treat Vitamin B12 deficiency?

If you are diagnosed with a Vitamin B12 deficiency, it is easy to rectify as B12 is very easy to replace. You may be prescribed a B12 liquid, or an intramuscular or subcutaneous injection may be necessary. You may need to have injections on a regular basis. You will also be advised to make changes to your diet to include foods rich in B12.

How we can help

If you feel you have some of the symptoms listed above, it’s a good idea to get tested for a Vitamin B12 deficiency. There are several blood tests that we can organise for you that will tell you if you are vitamin B12 deficient – Serum B12, Methylmalonic acid, Homocysteine and complete blood counts.

When you have been comprehensively tested, our expert Functional Medicine health practitioners will advise you in how you can make changes to your diet to optimise nutrition and fix the gut, as well as prescribe you the right supplements to restore your levels of Vitamin B12 and get you feeling like your old self again.


The above information is intended to be general, educational advice only, on topics which are of interest to us. It is not intended to represent specific or individual health or medical advice and is not specific to your situation. The below information is educative and is not intended to advertise any service.

Before making any decisions in relation to your health, you should always discuss your individual situation with your own health practitioners to ensure that any advice you have read is right for you.

Jarrod Cooper – ND

Jarrod Cooper – ND

Jarrod Cooper - ND is the founder of Advanced Functional Medicine Australia. He is a Naturopathic Doctor with extensive functional medicine training from leading practitioners in the USA and worldwide.

He is leading the way with advancements of functional medicine, clinically implementing worldwide best practices in Functional Medicine throughout Australia.

Jarrod consults in person from Perth, Western Australia and also online via Telehealth throughout Australia and worldwide.

If you are looking for personalised treatment, we highly recommend contacting Jarrod Cooper’s Advanced Functional Medicine clinic in Australia.

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