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Vitamin B12: Could it be the Missing Link with Infertility and Early Pregnancy Loss?

Updated: Jul 17, 2020

Vitamin B12 is a huge player in fertility and a deficiency in vitamin B12 is a major cause of recurring miscarriage, especially early pregnancy loss before 5 weeks. Yet it is rarely tested by general practitioners and fertility specialists. During my 10-year journey with secondary infertility and recurring pregnancy loss my B12 was not tested at all. Yet vitamin B12 plays an important role in folate metabolism and we all know how important folate is.

It was only later on in my journey that I realised the significance of B12 and arranged to get myself tested. This was just after my IVF miscarriage as I felt at the time that my mind was foggy and I couldn’t concentrate on anything. It was no wonder my B12 (and Iron) was low after IVF as I had so much blood drawn for blood tests during that period. B12 proved to be one of the missing links with me, especially as it is linked in clinical studies to recurring early pregnancy loss before 5 weeks which is something I was struggling with. When I did eventually get pregnant 3 years later, I needed high doses of B12 in the form of methycobalamin daily throughout my pregnancy.

So why is Vitamin B12 so important?

Vitamin B12 is an essential nutrient. It is works together with folate in the synthesis of DNA, RNA and red blood cells. Adequate levels of B12 maximise the uptake of folate. Vitamin B12 also helps to regulate brain activity and is involved in the production of the myelin sheath around the nerves and the conduction of nerve impulses. It is also important for methylation, an important liver detoxification pathway and reducing homocysteine levels. High levels of homocysteine levels in the blood can contribute to miscarriage and are caused by low levels of the methylation nutrients folate, B12 and B6. So supplying these nutrients can help to bring homocysteine levels down.

In female’s vitamin B12 also helps to boost the endometrium lining to prepare for implantation, which decreases the chances of complications.

What causes low B12?

Vitamin B12 is found mainly in animal foods such as meat, fish, dairy products and eggs however, even if you are eating meat a few times a day you can still become deficient if your body is unable to absorb it. Vitamin B12 can also be manufactured by our gut bacteria in the intestines although there is no evidence of how well absorbed or utilised this is.

The absorption process of vitamin B12 is complex and ` Uptake depends on gastric parietal cells excreting hydrochloric acid, intrinsic factor, and pepsin. Pancreatic enzymes and receptors in the distal ileum must be present along with the blood protein transcobalamin II to process B12. Lastly, the liver converts B12 to the active forms adenosylcobalamin and methylcobalamin for utilization' (Pacholok, 2013)

A deficiency of intrinsic factor, which is required for vitamin B12 to be absorbed in the intestines is a common reason vitamin B12 from food is not absorbed very well. Intrinsic factor is a mucoprotein enzyme produced by the parietal cells of the stomach (which also make hydrochloric acid). Any problems with the stomach as well as stress, inflammation, allergies and aging can reduce the production of hydrochloric acid and intrinsic factor. So for vitamin B12 to be absorbed a person must have a healthy, efficient digestive system.

Some of the most common causes of vitamin B12 malabsorption are:

· Leaky gut and inflammatory bowel disease

· Gut dysbiosis (imbalance in gut bacteria)

· Low stomach acid (hypochlorhydria)

· The auto immune condition pernicious anaemia - as the body attacks and destroys intrinsic factor, the protein that is essential for B12 absorption

· Acid suppressant medications

· Excessive alcohol

· Vegan or vegetarian diets (plant sources are poorly absorbed)

According to various studies 50% of long-term vegetarians and 80% of vegans are extremely low in B12. According to Chris Kresser (2011) B12 is the only vitamin that contains a trace element (cobalt), which is why it’s called cobalamin. Cobalamin is produced in the gut of animals. It’s the only vitamin we can’t obtain from plants or sunlight. Plants don’t need B12 so they don’t store it. A common myth amongst vegetarians and vegans is that it’s possible to get B12 from plant sources like seaweed, fermented soy, spirulina and brewer’s yeast. But plant foods said to contain B12 actually contain B12 analogs called cobamides that block the intake of and increase the need of true B12'.

Because vitamin B12 is stored in the body it can in some cases take about 5 years for some of the more severe symptoms to manifest.

Here are the typical symptoms of B12 deficiency:

· Weakness, fatigue, tiredness, generally feeling run down

· Poor memory, brain fog ,light headedness and dizziness

· Depression (is involved in the synthesis of serotonin and dopamine)

· Heart palpitations, shortness of breath

· Pale skin

· A smooth tongue

· Lack of appetite

· Constipation, diarrhoea, gas, bloating.

· Numbness, tingling in hands, legs and feet (as a result of nerve damage which is triggered by low oxygen levels in cells)

· Muscle weakness and coordination problems

· Mental problems such as depression, anxiety, memory loss, changes in behaviour

· Fertility issues and recurring early miscarriage

So if you have any of the above symptoms it would be worth getting your B12 levels tested by your health practitioner as you may need supplementation or B12 injections for more severe cases. If you are looking to take a B12 supplement look for one that contains sublingual methycobalamin which is the active coenzyme form of vitamin B12 that is more bioavailable than the common form cyanocobalamin. In New Zealand Solgar, Source Naturals and Clinicians have a sublingual B12 supplement in the form of methycobalamin that is available in most health shops. There are also a number of practitioner ranges that do higher dose supplements than what is available in health shops.

When you have been tested for B12 please do make sure you ask to see a copy of your test results. Levels of 500 pg/mL and above are optimal for fertility, pregnancy and miscarraige prevention. Unfortunately the reference range in New Zealand is lower than some other countries and 200 pg/mL and above is considered normal. Levels around 200 pg/mL are not really optimal for pregnancy and preventing early pregnancy loss though. Ideally you really need to be aiming for 500 pg/mL or above.

Please get in touch if I can help you in any way.


Kresser C (6/5/ 2011) B12 Deficiency: a silent epidemic with serious consequences -

Pacholok S M (13/12/2013) Vitamin B12 Deficiency: Serious Consequences -

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