Vitamin B12, also known as “cobalamin,” is a water-soluble essential nutrient required in our diet. When a nutrient is essential, it means the body cannot produce it internally so it must come from food we eat or supplemental form.

If you have type 2 diabetes, you could be at higher risk of a vitamin B12 deficiency. Vitamin B12 supports a healthy nervous system, brain and red blood cells and is needed only in very small amounts (2.4 mcg/day). 

Vitamin B12 deficiency

Vitamin B12 is found only in meat, poultry, fish, eggs, and dairy, which is why vegetarians and especially vegans are at higher risk for deficiency and should take a dietary supplement that includes B12. While there is no set upper limit for B12, it is useless to supplement if you do not have a deficiency.

Blood levels <200 pg/mL are generally considered deficient while >400 pg/mL are sufficient. Between this range, you may want to consider supplementation. Dosing will vary depending on level of deficiency, but is often 1-2 mg daily. In some cases mega-dose injections every month are required, depending on how the person responds to supplementation or if there is a severe deficiency.

What Does Vitamin B12 Do?

Vitamin B12 plays a number of very important roles in our bodies:

  1. It is necessary for the metabolism of amino acids and fatty acids
  2. It is required for DNA synthesis
  3. It helps synthesize neurotransmitters (ie serotonin and dopamine)
  4. It is essential for cardiovascular function

Vitamin B12 Deficiency and Type 2 Diabetes

It’s estimated that 22% of people with type 2 diabetes have Vitamin B12 deficiency, which is much higher than the general population.

Getting enough Vitamin B12 in your diet through the food you eat is only one piece of the picture. After it has been ingested, the B12 then needs to be absorbed from the gut into the body, then travel to the cells to do its work. Vitamin B12 requires something called “intrinsic factor” (a protein secreted by special cells in the stomach) in order to be absorbed from the lumen of the gut into the body. Some people don’t make as much intrinsic factor, and generally speaking, as we get older, we make less and less, which is a reason why the elderly are at higher risk for B12 deficiency, too.

Additionally, metformin (a first line drug commonly used in diabetes treatment), is one of many medications that interferes with absorption of Vitamin B12. It has been estimated that 10-30% of people who take metformin may not be able to absorb Vitamin B12. Another study showed that 75% of metformin users were deficient. Whether the range is 10% or 75%, it's still something to be concerned about – if you're taking metformin, you are at higher risk for B12 deficiency.

Interestingly, it also seems to be the case that B12 deficiency may cause hyperglycemia (high blood sugar levels) so there may be a bit of a cyclical relationship between the two.

One of the complications of type 2 diabetes is neuropathy (numbness/pain that often first appears in the hands and feet). Neuropathy is experienced by about 30% of people with diabetes. Deficiency of B12 is associated with neuropathy as well and it can be difficult to tell which may be causing the symptoms or if both may be contributing.

People who have had bariatric surgery are at high risk for deficiency also, since their absorptive area has been reduced and the portion of the stomach that secreted intrinsic factor may be gone or destroyed.

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Vitamin B12 Deficiency and Type 2 Diabetes - Are you at risk?

Signs of Vitamin B12 Deficiency

Early signs of vitamin B12 deficiency may include:

  • Tiredness
  • Weakness
  • Weight loss (unintentional)
  • Loss of appetite
  • Constipation
  • *B12 deficiency can also be asymptomatic or without symptoms, especially in early stages

If left untreated, long term B12 deficiency can lead to:

  • Permanent brain and nerve damage
  • Memory Loss
  • Dementia
  • Depression
  • Immobility

Diagnosing Vitamin B12 Deficiency

If you think you might have B12 deficiency, discuss your symptoms with your doctor and request he/she test your levels. There is a very simple blood test and treatment is as easy as supplemental doses.

There are several options for supplementing. Oral pills or sublingual (means ‘under the tongue’) options are available over the counter. Often, if intrinsic factor is lacking, periodic mega-dose B12 injections are administered. These shots are given into the muscle and are very effective. Obviously this would have to be performed in your doctor’s office.

If you are a vegetarian or vegan, over the age of 50, have any medical issues with absorption (including any type of gut surgery or condition), or take metformin, you are at much higher risk and should be tested regularly.

Top Sources of Dietary Vitamin B12

  • Liver
  • Clams
  • Caviar
  • Fish – mackerel, herring, salmon, tuna, cod, trout
  • Crab
  • Organ meats – kidney, heart, giblets, brains
  • Eggs
  • All meats and poultry

Include the above foods regularly in your diet and your intake of B12 should be sufficient. If you're a vegetarian or especially a vegan, it is highly recommended you take a supplement.

There are also other food items that have been fortified with B12 such as: nutritional yeast, breakfast cereals, breads and sometimes tofu – but in many cases, these are foods we would not necessarily recommend for a low carb T2 diabetic diet. Stick to the natural food sources because they are a much better option.

Just know though, if you are deficient in vitamin B12, it is very unlikely you will be able to correct the problem through food alone, but will likely need to include a supplemental form, at least for a time.

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