Dr. Patricia Yarberry Allen is a collaborative physician. This week, she asks gastroenterologist Brian Landzberg—who is affiliated with the Weill Medical College of Cornell University, New York–Presbyterian Hospital, and Hospital for Special Surgery—to advise a patient who has just been diagnosed with a worrisome-sounding condition called “pernicious anemia.”


Vitamin B12

Dear Dr. Pat:

I am 52 and was recently told by my GP that I had some mild anemia. I had been feeling fine. I had my blood work last done three years ago. I had my last period three years ago and am doing fine, without any menopausal symptoms that I am aware of. Over the last four months, however, I noticed increasing hair loss and increasing fatigue, and I don’t seem to think as clearly as I used to—but it was nothing I could put my finger on.

The GP did basic bloods and found out that I was anemic—mildly anemic, he told me. I needed my first colonoscopy, so the GP referred me to a gastroenterologist for this test. The GI doctor looked at my blood work and decided to do some more bloods to see what might be causing my anemia. He found out that I was low on B12.

I do have two drinks a night and the GI doctor said that might have something to do with the low B12. The blood work also showed that I am positive for antibodies to parietal cell antibodies, and have low Vitamin D. The GI doctor plans to do a colonoscopy, but also another test, an endoscopy.

Could you explain why I might have these problems, why people become anemic when they don’t have enough B12 in their blood, and what supplements in general a woman my age should have been taking. Is there anything else I should have done to prevent this? Is it related to my hair loss?


Dr. Landzberg Responds:

Dear Betty:

Thanks for your questions. Your physicians are appropriately considering the diagnosis of pernicious anemia (PA), a disease that retains its historical, but now unduly frightening, name. PA is an autoimmune disease that, by attacking parietal cells in the stomach lining, effects low gastric acid secretion and an inability to absorb vitamin B12. Now that we know that the mechanism of the disease is low vitamin B12, progression can be easily averted by B12 repletion through injections, nasal spray, sublingual supplements, etc. B12 is critical to make the building blocks of DNA, and is a vital nutrient for red blood cells (along with iron and folic acid) and for the brain and nerves. The symptoms of B12 deficiency are myriad and include pallor, imbalance, weakness, fatigue, tingling, mood change, dementia, and probably hair loss.

The history of PA is a fascinating one. There was a time when its name was earned. Physicians would watch people become increasingly pale and weak and slowly fade away. It was hard for them to believe that this would be a nutritional deficiency, because the patients did not look as if they were malnutrition/malabsorption patients:  Many were overweight, and they didn’t generally suffer from diarrhea. This is because PA is a selective B12 malabsorption. The gastric parietal cells, which make the “Intrinsic Factor” (IF) needed to absorb B12 in the later intestine, are absent. Historically, it was observed that having PA patients consume massive amounts of ground beef and liver (excellent sources of B12) was mildly helpful, but that consumption of the same foods with gastric juice taken from healthy patients led to dramatic improvement. There was an IF in the normal gastric juice needed to hold onto B12. Today, when B12 is supplemented by injection or nasal spray, the digestive tract is bypassed and IF is not needed.

Remember that not all B12 deficiency is due to PA. Many patients, especially vegans, simply don’t consume the vitamin, which occurs mainly in animal sources. Others malabsorb it due to intestinal processes, such as Crohn’s disease, surgical resections, bacterial overgrowth, and, less commonly, celiac disease.  Excessive alcohol consumption and acid-blocking medications may also contribute.  PA, specifically, is usually diagnosed by low B12 levels, serologies (Anti-IF and anti-parietal cell antibodies), and upper endoscopy that finds autoimmune gastritis and atrophy, along with, on biopsy, absent parietal cells and inadequately acidic gastric juice pH.

Because PA is a chronic inflammation of the gastric lining, there is a mildly increased risk of gastric cancer in the long term. I generally recommend a surveillance upper endoscopy at initial diagnosis, then every five years afterward. I also make sure to do a careful look at, and biopsy of, the terminal ileum (last part of the small intestine) when performing the colonoscopy looking for other causes of B12 malabsorption.  Occasionally, elevated methylmalonic acid and homocysteine levels may be helpful in diagnosing B12 deficiency when B12 levels are in the low-normal range.

If your levels are low, B12 should be aggressively repleted and rechecked.  However, since B12 deficiency can produce a variety of common symptoms, it has often been used inappropriately as a panacea, or cure-all, for everyone who has fatigue. If your levels are well in the normal range, boosting them with tonics of B12 would not make you feel stronger or better, other than through a placebo effect. Your question as to which supplements, in general, are advisable is a topic for another discussion; the answers will vary based on age, gender, risk factors for osteoporosis or heart disease, and many other factors.

Once the diagnosis of PA is made, and with these interventions, PA should not be pernicious anymore.

Dr. Landzberg



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  • Robbie Wendorff October 16, 2021 at 9:17 am

    Yes, love this place good article