Vitamin B-12 Deficiency

Pernicious Anemia & B-12 Deficiency Anemia

Jeremy Schmidt

4/29/2015

Introduction

Pernicious anemia and B-12 deficiency anemia are conditions that lead to your body producing

an insufficient amount of functioning red blood cells.1 It is a type of anemia that does not

respond to iron supplementation because its symptoms are caused by a deficiency in vitamin B-

12. These types of anemia were first studied during the 1920’s by George Minot and William

Murphy, who concluded that some types of anemia could be treated by feeding people cooked

liver daily, liver being a great source of vitamin B-12. If these types of anemia are left untreated,

a deficiency in vitamin B-12 can lead to megaloblastic anemia and permanent neurological

disorders.

Vitamin B-12

Vitamin B-12, also known as cobalamin, is a water soluble vitamin that your body needs for

DNA synthesis and proper nerve and blood cell functioning.2 To absorb vitamin B-12 from food,

the parietal cells that make up your stomach lining secrete two compounds, hydrochloric acid

(HCl) and intrinsic factor.3 HCl is a strong acid that aids in digestion by converting the enzyme

pepsinogen to its active form pepsin. Both Pepsin and HCl break apart protein, releasing vitamin

B-12.4 Intrinsic factor is a protein that binds to vitamin B-12 in the stomach, making it

bioavailable for the body to absorb. Vitamin B-12 by itself will just be excreted as waste and

needs this protein in order to be absorbed through the small intestines. Roughly 1% of the oral

vitamin B-12 you consume is absorbed passively in the absence of intrinsic factor.5 B-12 is

stored and recycled more efficiently than most other water soluble vitamins, so a deficiency is

usually caused by malabsorption.4 A person eating a non-vegan diet can store up to 2,000 – 3,000

micrograms of B-12 and multiple studies conclude that on average, 0.1 - 0.2% (about 3

micrograms) of B-12 is lost from the body each day.6 A healthy person’s liver will secrete B-12

into bile which is needed to digest fat. The intestines can reabsorb roughly 0.7µg of the B-12

released in the bile.6 Once absorbed in the body, vitamin B-12 becomes converted into one of

two coenzymes, methylcobalamin and adenosylcobalamin.4 These two coenzymes are important

in energy metabolism and in the conversion of homocysteine to the amino acid methionine.5 The

conversion of homocysteine to methionine is important because methionine is a universal methyl

donor for DNA and RNA.5 Vitamin B-12 can be produced in the large intestines as a byproduct

of bacterial metabolism, however it cannot be absorbed because the only site of vitamin B-12

absorption is within the ileum, the last eleven feet of the small intestines.

Pernicious Anemia Etiology

Pernicious anemia is an autoimmune disorder that attacks the parietal cells and intrinsic factor of

the stomach, leading to gastric atrophy. This reduces the amount of vitamin B-12 that can be

absorbed. Antibodies produced by the body target a specific pump along the plasma membrane

of parietal cells called the gastric proton pump (H+/K+ - ATPase), causing the breakdown of the

stomach lining.2 Because these proton pumps secrete acid, the damage to the stomach lining

caused by these antibodies leads to decreased acid production.2 The occurrences of the antibodies

that attack these pumps are more frequent during the early stages of pernicious anemia. If this

disease is left untreated, the prevalence of these antibodies decreases due to the decreased

number of parietal cells left in the stomach. If the stomach loses too many of these cells, then

there will be a decreased production of stomach acid and intrinsic factor, making vitamin B-12

less bioavailable. Intrinsic factor has a high affinity for vitamin B-12, forming an IF-vitamin B-

12 complex that travels to the ilium where it is absorbed. Seventy percent of patients with

pernicious anemia have antibodies that attack the active site of the ilium, preventing its

absorption along the small intestine.2

Pernicious Anemia Incidence

Pernicious anemia is a condition that affects 1-2% of older adults.5 Due to the recycling and

storing properties the body has on vitamin B-12, symptoms of pernicious anemia are not usually

seen until after age 30, the average age of diagnosis being age 60.1 Both males and females are

equally as likely to get pernicious anemia. You are more likely to get this disease if you have

ancestry from northern Europe or Scandinavia.1 You can also acquire it hereditarily if you have a

family history. Researchers Callender and Denborough observed the family histories of 142

patients with pernicious anemia and found that 19% had at least one member of their family

affected with this anemia.7 Recent studies show that specific expression of genes might cause

this disease. Specific forms of a gene (alleles) that are located in the Major Histocompatibiliy

Complex (HLA) are associated with pernicious anemia and other autoimmune diseases.7 The

genotype HLA-DRB1*03 and HLA-DRB1*04 have been shown using sequence specific

oligonucleotide probes, to be associated with autoimmune diseases.2 As of now, the mechanism

of why these genes cause pernicious anemia is unknown. Most of the studies that have been

conducted on gene expression are correlation causation studies, showing that people with

autoimmune diseases have these alleles. This does not necessarily prove that it’s this expression

of the gene that causes pernicious anemia and should be taken lightly when making a diagnosis.

General B-12 deficiency anemia Etiology and Incidence

There are several disorders and factors that can lead to a vitamin B-12 deficiency. These factors

include celiac disease, alcoholism, surgeries, antacids, H. pylori, age and diet. Though there are

cases of vitamin B-12 due to factors not listed below, here are seven of the most common

reasons someone would be vitamin B-12 deficient.

Celiac disease - A person with celiac disease will have trouble absorbing vitamin B-12 because

this disorder typically results in the malabsorption of nutrients. The immune system in those with

celiac disease attacks the villi of the mucosa lining of the small intestine when gluten is

consumed, causing inflammation and reduced surface area for nutrients to be absorbed.8 If the

Ileum of the small intestines is damaged, then vitamin B-12 absorption will decrease.

Chronic Alcoholism - Alcohol interferes with nutrient absorption by causing inflammation in the

stomach, pancreas, and intestines.4 This inflammation causes damage to the intestinal mucosa

which allows large molecules to pass into the blood stream. These large molecules cause even

more stress to the liver, resulting in a decreased rate of micronutrients metabolized.4

Surgeries - Surgeries such as a gastrectomy that takes out part of the stomach will decrease

vitamin B-12 absorption because of the reduced number of parietal cells available to produce

HCl and intrinsic factor. Surgeries that remove part of the Ilium also contribute to a deficiency.

Antacids - Taking antacids can decrease B-12 absorption. Antacids neutralize stomach acid

which plays a role in the breakdown of protein. Stomach acid is needed to activate pepsinogen to

pepsin, which is the primary protein digesting enzyme of the stomach. If pepsin is not active,

then vitamin B-12 will remain bound to protein and never bind to intrinsic factor.

H. pylori - In recent studies, the role of Helicobacter pylori (H. pylori) has been correlated to

patients with gastritis and even 30% of patients with pernicious anemia.9 H. Pylori are a type of

bacteria that thrive in the stomach. It acts like a pathogen, causing inflammation and cell damage

to the stomach lining.9 This bacterium produces multiple pathogenic factors including cytotoxin-

association gene A (cagA) which causes an immune response in the stomach.9 The purpose of

this pathogenic factor is to facilitate the bacteria’s survival and aid in cell adhesion along the

stomach lining. The human immune system responds to cagA by sending neutrophils and T cells

to defend against the pathogen. The effect of overexposure to neutrophils on the stomach lining

leads to cell damage because neutrophils release oxyradicals which have the potential to destroy

surrounding tissue as well as foreign bacteria. These oxyradicals can lead to the gastritis

associated with B-12 deficiency anemia. H. pylori has an enzyme to block this type of oxidative

stress, protecting it, causing the gastritis to become chronic.9

Age - Most of the people diagnosed as vitamin B-12 deficient are older adults, affecting 10-15%

of people over the age of 60.10 As we age, some people lose their appetite which can lead to

malnutrition in general if the person isn’t eating enough. Vitamin B-12 is found mainly in meats.

Some older adults find meats to become difficult to chew as they age due to edentulous (a loss of

teeth). They might also find meat to be dry and tasteless since they aren’t producing as much

saliva as they once were. Due to these factors, older adults might avoid sources of vitamin B-12

without realizing it. Hypochlorhydria (which is more prevalent in the elderly), in those who have

untreated atrophic gastritis will cause an increased risk of vitamin B-12 deficiency because of the

decreased amount of stomach acid produced. A decrease in stomach acid can also cause SIBO,

small intestinal bacteria overgrowth. The bacteria in the small intestines will decrease vitamin B-

12 absorption by metabolizing it before your body has a chance to.8

Diet - Those following a vegetarian or vegan diet are also at higher risk of becoming vitamin B-

12 deficient. Plant based foods do not contain vitamin B-12, so supplementation is needed for

these groups. Vitamin B-12 is important for fetal development. An infant who does not get

enough vitamin B-12 from the mother during pregnancy might become vitamin B-12 deficient

soon after birth, showing severe neurological damage. Vitamin B-12 can freely cross the

placenta during pregnancy and is found in breast milk. Pregnant and/or breastfeeding women

who follow a vegan diet will have low vitamin B-12 reserves to begin with. The additional

vitamin B-12 needs of the growing baby has the potential to cause vitamin B-12 deficiency

symptoms in these vegan mothers.5

Pernicious Anemia and General Vitamin B-12 deficiency Symptoms

Anemia - The physical symptoms of pernicious anemia are due to the deficiency of vitamin B-

12. Since this vitamin is involved in DNA synthesis, the number of blood cells produced

decreases and the formation of abnormal red blood cells increases. A deficiency in B-12 causes a

mutation in a gene causing megaloblastic anemia (abnormally large red blood cells).2 The

combination of megaloblastic anemia and decreased levels of RBC’s can cause fatigue and

shortness of breath. This fatigue occurs because of the lack of functioning RBC’s available to

carry oxygen through the body.

Neurological disorders - Vitamin B-12 is also involved in the myelination of nerve axons. A

deficiency causes nervous system issues due to demyelination, which can progress to neuronal

death.2 Numbness and tingling of hands and feet are the beginning symptoms of nervous system

damage.1 This can eventually lead to confusion, depression, loss of balance, dementia in severe

conditions and death if left untreated.11

Cardiovascular disease and Alzheimer’s – It has been noted that those with cardiovascular

disease and Alzheimer’s have elevated levels of homocysteine in the blood. The conversion of

the amino acid methionine to the amino acid cysteine requires a step in between resulting in the

formation of homocysteine. Homocysteine can then go through one of two pathways. It can be

converted to cysteine or it can be converted back to methionine depending on the body’s need for

the two chemicals. However the conversion back to methionine requires both vitamin B-12 and

folate, or an increase in homocysteine will result. Other symptoms include constipation, diarrhea,

pale skin, poor memory, confusion, depression, swollen/red tongue or pica (the desire to eat non-

food items).1

Diagnosis

Vitamin B-12 levels are obtained from the blood and values below 170-250pg/mol (120-

180picomol/L) indicates a vitamin B-12 deficiency. However, checking blood serum levels can

be inaccurate, so other tests are done alongside to improve accuracy. An MMA test, which stands

for methylmalonic acid, is another option to diagnose B-12 deficiency. In the body, the

combination of methylmalonic acid and B-12 is used to produce acetyl CoA. When vitamin B-12

levels fall, methylmalonic acid levels rise.11 Doctors also perform this test alongside

homocysteine tests since B-12 is involved in the conversion of homocysteine to the amino acid

methionine. Methylmalonic acid levels greater than 0.4micromol/L and homocysteine levels

greater than13micromol/L suggests a vitamin B-12 deficiency.5 Homocysteine levels should not

be checked by itself because a diet high in folic acid can interfere with the readings.

For diagnosing pernicious anemia, tests are done looking for antibodies against parietal cells. To

test for a deficiency in intrinsic factor, a doctor might perform a Schilling test. This test involves

a patient consuming an isotope of B-12 following an injection of B-12 or supplemental intrinsic

factor to test the degree of pernicious anemia. With this test, doctors can tell whether you have

problems absorbing B-12 in the small intestine or if it is due to parietal cell damage.

Gastric biopsies/endoscopies, stool fecal tests are also common ways to check for H. pylori

infection.9 Histological staining, rapid urease test and PCR can be done once samples are

collected from the stomach and small intestine to determine if H. pylori is the cause of the B-12

deficiency.

Treatment of Pernicious Anemia and General B-12 Deficiency

For general B-12 deficiencies due to a vegan/vegetarian diet, supplementing oral doses of B-12

is enough. For deficiencies caused by gastric biopsies or surgeries where part of the stomach or

intestine is removed, some people benefit with high oral doses of B-12, however the gold

standard is parental injections of B-12. Oral doses of 1000-2000µg B-12 have shown to improve

symptoms associated with anemia and neurological symptoms.12

Since decreased levels of gastric secretions and intrinsic factor are associated with pernicious

anemia, B-12 injections are needed.2 There is no cure for pernicious anemia so lifelong B-12

injections once a month are needed.12 If damage to the stomach and intestines is not severe, oral

B-12 might be given to those with pernicious anemia. “Initial oral doses of 2000 mcg of oral

vitamin B-12 daily, followed by a decreased daily dose of 1000 mcg and then 1000 mcg weekly

and finally, monthly might be as effective as intramuscular administration” according to the

National Institutes of Health.4 Treatment for B-12 deficiency in those suffering from crohn’s

disease, celiac or alcoholism might no longer be needed once the underlying disease causing the

deficiency is treated.12

Drug/Nutrient Interactions

There are multiple medications and chemicals that can interfere with vitamin B-12 absorption.

Folate, chloramphenicol, proton pump inhibitors, and H2 receptor antagonists have been shown

to reduce the amount of B-12 absorbed in the body. People taking these medications should be

carefully monitored by their healthcare provider for possible B-12 deficiency.

Folate - Vitamin B-12 is needed to convert folate into its active form in the body.4 Not having

enough vitamin B-12 can cause a secondary deficiency of folate. Folate, like vitamin B-12, is

necessary for DNA syntheses and can cause macrocytic anemia if you are deficient.4 With

fortified foods becoming more popular, folic acid (the active form of folate) is added to foods

and can mask a B-12 deficiency. When a person with vitamin B-12 deficiency consumes enough

folic acid, the anemic symptoms of a B-12 deficiency will go away, which may delay diagnosis.4

The delay can cause an increased risk for nerve damage since folate does not help against the

neural damage associated with the lack of B-12. If left untreated, nerve damage due to B-12

deficiency can become permanent within 6 months after symptoms appear.12

Chloramphenicol - Antibiotics, if used over a long period of time can decrease vitamin B-12

absorption. In particular, the antibiotic chloramphenicol may interfere with vitamin B-12 because

one of the side effects of this antibiotic is decreased RBC production which has an antagonistic

effect towards the erythropoiesis effects of B12.4

Proton Pump Inhibitors - Proton pump inhibitors such as Prilosec used to treat gastric reflux are

shown to reduce B-12 absorption because they decrease the amount of stomach acid produced.3

Other medications that increase the pH in the stomach should be avoided if you are deficient in

B-12.

H2 receptor antagonists – Histamine H2 receptor antagonists such as cimetidine, fomatidine and

ranitidine can interfere with B-12 absorption. These medications are used to treat peptic ulcers

by blocking the action of histamine on parietal cells, slowing the release of hydrochloric acid

into the stomach.

Diet Therapy recommendations

The recommended intake for vitamin B-12 is provided by the dietary reference intakes (DRIs),

developed by the Food and Nutrition Board at the Institute of Medicine.5 The DRIs are a set of

nutritional values of nutrients based off the average needs of healthy individuals. There is no

tolerable upper limit associated with vitamin B-12, and no toxic effects have been reported with

intakes of 100µg/day.4 The dietary reference intake for vitamin B-12 is 2.4µg/day for adults.3

The DV of vitamin B-12 is 6.0mcg, 3.6mcg over the daily reference intake. The daily value (DV)

is much like the DRIs however; the daily values of nutrients were developed by the FDA to be

placed on food labels and are recommendations based off a 2000kcal diet. The only dietary

sources that have vitamin B-12 are animal based sources.3 Organs such as the livers of animals

are high in vitamin B-12, but the meat also contains a considerable amount. Mollusks/clams

contain 50µg (824%DV) per 100g. Beef has 5.0µg (84%DV) per 100g. Tuna has 3µg (50%DV)

per 100g. Salmon has 2.8µg (47%DV) per 100g. Eggs have 1.3µg (22%DV) per 100g. Milk has

0.4µg (7%DV) per 100g.13

One Day Food Menu

Breakfast:

Whole wheat bagel with

o 2 fried eggs or scrambled

o ¼ cup Tomato slices

o ½ cup Spinach

2 cups of skim milk (or milk

alternative)

1 Banana

Alternate breakfast:

One serving of whole grain cereal

fortified with B12

2 cups of milk (or milk alternative)

½ cup of berries

Lunch:

Salad

o 2cups spinach/leafy green

Alternative lunch:

Spaghetti and meat sauce

o 3oz whole grain spaghetti

o 1 chopped avocado

o ¼c sliced vegetable of choice

o 1 serving of (low calorie) salad

dressing

o 2oz sliced chicken

1 Apple

o 3oz Ground beef

o 1 serving of tomato sauce

1 Apple

1 serving of yogurt

Dinner:

Clams and linguini

o 2oz of clams

o 2 servings of butter/oil

o 3oz of whole grain linguini

o 1 serving of parmesan cheese

1 cup of green beans

Alternative dinner:

Salmon with baked potato

o 3oz salmon

o 4oz baked potato

o 1 serving of butter (or butter

altnerative)

2 cups of broccoli

Snack:

One serving of yogurt

Alternative snack:

1 cup of fruit of choice

Based on the main menu (not the alternative), the total calories came to 2050kcal. If the person is

physically active, adding more clams or chicken will increase the calories to accommodate for

the calories expended and also increase the amount of B-12 in the diet. The diet contains 7.5oz of

whole grains, 2.5cups of vegetables, 2.25cups of fruit, 3cups of dairy and 6oz of protein. All of

the categories meet the MyPlate recommendations for a 40 year old male who is active less than

30min/day. The B-12 content is 35µg, 32.5µg over the recommendation.

Conclusion

Both pernicious anemia and general B-12 deficiency anemia are caused by the malabsorption of

vitamin B-12. The side effects of a B-12 deficiency don’t appear until later in life, so diagnosing

early on is rare. To prevent general B-12 deficiency anemia, a diet that doesn’t exclude meat

should be consumed. If symptoms appear, treatment should be given as soon as possible since

there is a possibility of nerve damage if the body doesn’t have enough B-12. There is no cure for

pernicious anemia, so lifelong treatment is necessary. For those suffering from general B-12

deficiency anemia, there is a possibility that consuming a diet high in vitamin B-12 will cure the

disease.

Citations

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2. Nicola B, Antonio A. Diagnosis and classification of pernicious anemia. Autoimmunity Reviews. January 2014; 13(4-5):565-568. http://www.sciencedirect.com/science/article/pii/S1568997214000548

3. Vitamin B12. National Institute of Health. http://ods.od.nih.gov/factsheets/VitaminB12-Consumer/ Updated June 24, 2011. Accessed February 9, 2015.

4. Vitamin B12. National Institutes of Health. http://ods.nih.gov/factsheets/VitaminB12-HealthProfessional/ Accessed February 6, 2015.

5. Smolin L, Grosvenor M. Nutrition – Science and Applications. Danvers, MA: John Wiley & Sons, Inc.; 2013.

6.  Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000.

7. Banka S, Ryan K, Thomson W, Newman W. Pernicious Anemia – Genetic insights. Autoimmunity Reviews. February 2011; 10(8): 455-459. http://www.sciencedirect.com/science/article/pii/S1568997211000243

8. Celiac Disease. National Institute of Diabetes and Digestive and Kidney Diseases. http://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/celiac-disease/Pages/facts.aspx. Published September 2008. Accessed February 20, 2015.

9. Varbanova M, Malferthiener P. Chronic gastritis – An update. Best Practice & Research Clinical Gastroenterology. December 2014; 28(6): 1031-1042. http://www.sciencedirect.com/science/article/pii/S1521691814001565

10. Baik HW, Russell RM. Vitamin B12 Deficiency In The Elderly. Annual Review of Nutrition. July 1999; 19: 357-377. doi: 10.1146/annurev.nutr.19.1.357

11. Anemia – B12 deficiency. MedlinePlus. http://www.nlm.nih.gov/medlineplus/ency/article/000574.htm Updated February 24, 2014. Accessed February 9, 2015

12. McMullin MF, Young PB, Bailie KE, Savage GA, Lappin TR, White R. Homocysteine and methylmalonic acid as indicators of folate and vitamin B12 deficiency in pregnancy. International Journal of Laboratory Hematology. December 20, 2001; 23(3) 161-165. doi: 10.1046/j.1365-2257.2001.00370.x

13. Foods highest in Vitamin B12. Self Nutrition Data. http://nutritiondata.self.com/foods-000116000000000000000.html. Accessed February 20, 2015.