Do carnivores need Vitamin B12 supplements?

People who defend eating animal products as necessary for health have two swords, protein and Vitamin B12. We are getting smarter about protein and many people now accept that plant foods are a healthier source of protein, but most people including health care professionals are confused about B12. It is true that animal products contain B12, and strict vegetarians/vegans are at risk for B12 deficiency, but absorbing B12 from animal products is a very complex process and people who eat meat may be at equal or greater risk for B12 deficiency.

The Framingham Offspring study found that 39 percent of the general population may be in the low normal and deficient B12 blood level range, and it was not just vegetarians or older people. This study showed no difference in the B12 blood levels of younger and older adults.  Most interestingly there was no difference between those ate meat, poultry, or fish and those who did not eat those foods. The people with the highest B12 blood levels were those who were taking B12 supplements and eating B12 fortified cereals.

Understanding why people who eat animal products may have low B12 levels requires a little knowledge of how we get B12. It is made by bacteria that live in soil and in the guts of animals. Cattle and other grass-eating animals get B12 and B12 producing bacteria from clumps of dirt around the grass roots that they pull up. Chickens and other birds get B12 from pecking around for worms and other insects. These animals store B12 mostly in their livers and muscles and some B12 pass into milk and eggs.

But, cattle no longer feed on grass and chickens do not peck in the dirt on factory farms. Even if they did, pesticides often kill B12 producing bacteria and insects in soil. Heavy antibiotic use kills B12 producing bacteria in the guts of farm animals. In order to maintain meat a source of B12 the meat industry now adds it to animal feed, 90% of B12 supplements produced in the world are fed to livestock. Even if you only eat grass-fed organic meat you may not be able to absorb the B12 attached to animal protein. It may be more efficient to just skip the animals and get B12 directly from supplements.

Cattle feeding (USDA Gallery)
Cattle feeding (USDA Gallery)

B12 attaches very tightly to animal protein. Strong stomach acids are needed to break down the protein so that B12 can get into your blood. Over the counter antacids and prescription drugs that reduce stomach acids block the breakdown of protein and the release of B12. These drugs are among the most commonly used and prescribed drugs in the US. Proton pump inhibitors such as Prilosec were the most commonly prescribed class of drugs in 2012. Nexium brought in over 6 billion dollars and was the top selling drug in 2012, according to IMS Health. A lot of people have “heartburn” and most of them are people who eat meat. “Zero heartburn” may mean zero B12 absorption.

Once B12 is free it has to quickly attach to a carrier from saliva and the stomach. This carrier protects it from being destroyed by stomach acids and takes it to the alkaline environment of the duodenum which is the first part of the small intestine. In the duodenum B12 gets freed again by enzymes from the pancreas. Free B12 from food must then attach to another carrier called Intrinsic Factor (IF) to get absorbed from the intestines into the blood stream. If you’re lost just reading this you can see how B12 from food can be lost.

Intrinsic Factor (IF) is made by parietal cells in the stomach. Lack of IF causes the classic B12 deficiency disease called Pernicious Anemia where the body makes antibodies to parietal cells and destroys them. Some B12 from food can still be absorbed but much less efficiently.

Until recently there was no explanation for autoimmune disorders like pernicious anemia but new research suggests that eating animal products causes animal sugars such as Neu5gc to become attached to the human cells that line hollow organs such as the stomach.

Our immune system sees any cells with animal sugars on them as foreign and makes antibodies to destroy them. This attack by our immune system causes chronic inflammation and may explain many conditions such as atrophic gastritis that destroys both the acid-producing cells and the IF-producing cells in older people who eat meat but do not abuse alcohol.

Weight loss surgery and banding procedures that bypass most of the stomach and the duodenum also bypass the places where B12 processing for absorption occurs. This decreases the ability to absorb B12. As a result over 30 percent of gastric bypass patients will develop B12 deficiency even with oral B12 supplements and may need B12 injections. There are obese vegans but the majority of people who have weight loss surgery and subsequent B12 deficiency eat animal products.

If you can free B12 in the stomach and again in the duodenum and you have enough IF and they are able to hook up, the IF-B12 combo has to travel all the way to the end of the small intestine to an area called the ileum to be absorbed into the blood. No matter how much steak you eat the ileum will only absorb a very small amount of B12 at a time, about 1.5 to 2 micrograms every 4 to 6 hours (a microgram (mcg) is a millionth of a gram).

In addition to the B12 that is attached to IF, about 1% of any amount of free B12  in the ileum will also be absorbed by passive diffusion, meaning that it will just pass through the intestinal wall to the blood without any help. Since most B12 from food attaches to IF and have to wait their turn for receptors in the ileum, the best way to increase the amount of B12 absorbed is to increase the amount of free B12 available. The best way to do this is to take B12 supplements.

The ileum is also where B12 is reabsorbed with bile to keep it in the body. Bile is made in the liver, stored in the gallbladder and sent into the duodenum to help digest fatty foods. When the fatty food digestion is done bile goes back to the liver through the ileum. Some of the B12 stored in the liver gets into bile and would be lost in feces if the body did not get it back with bile. This constant recycling of bile and B12 is called the enterohepatic circulation. It maintains B12 stores in the body. Most people have about 3 years of stored B12 reserves but the constant recycling makes what we have last for about 7 to 10 years longer.

Chronic inflammatory bowel diseases such as Crohn’s Disease affect the ileum and impair B12 absorption. These diseases are only seen in people who eat animal products and they improve when meat is removed from the diet.

Type 2 Diabetes is a common condition among people who eat animal products. Metformin is a first line treatment drug for type 2 diabetes. Metformin blocks the uptake of the B12-IF combo in the ileum. People who use of Metformin for more than three years will develop a B12 deficiency if they don’t take supplements. This is a problem because B12 deficiency and diabetes can both cause neurological problems, the early symptoms of B12 deficiency may be mistaken for the symptoms of diabetes. Calcium is also needed for B12 absorption in the ileum and there are excellent cholesterol-free food sources of calcium. If you are on Metformin ask your doctor to test for B12 deficiency and be sure to take B12 supplements.

The ileum empties into the colon. Human colon bacteria make lots of active B12, but it cannot be absorbed through the colon wall or make it back to the ileum; it is excreted in feces. Other herbivores like rabbits have the same problem as humans; they produce B12 downstream from where it is absorbed. Just like humans they develop atherosclerosis and clogged arteries when they eat cholesterol-containing animal products.  Rabbits solved their problem by producing 2 types of feces, regular hard pellets during the day that are discarded and soft B12 rich caecotrophs that they eat as soon as the pass them, usually at night.

Our ancestors solved the B12 problem by using human feces as manure called “night soil.” They got B12 from fecal crop contamination but they probably also got some foodborne illnesses. If this sounds gross and the prospect of eating feces to get B12 is not appetizing, then you have to re-think your food choices, 92% of chicken in supermarkets have fecal contamination and it can only get worse. USDA is moving to an honor system for meat inspection where the meat industry inspects itself.  You can skip the poop, cholesterol and atherosclerosis by just taking a B12 supplement.

So, what does B12 do and why do we need it?

Understanding the functions of B12 requires a biochemistry course but basically it is an enzyme co-factor (helper) for 2 reactions. One reaction converts methylmalonic acid (MMA) to succinic acid and the other reaction regenerates the amino acid methionine from homocysteine and generates the active form of another vitamin, folic acid. That’s it, that is all it does but those 2 reactions affect every cell in our bodies and produce substances that are essential for normal human life.

Lack of B12 shows up as three main problems:

1. Lack of energy

2. Unraveling of myelin and destruction of nerve cells

3 Anemia with abnormal blood cells.

Myelin is the fatty substance that protects and insulates nerve cells. Any nerves can be affected; symptoms depend on the affected nerves. If the brain is affected it can cause memory loss and confusion, if the optic nerve is affected it can cause blindness, but most commonly the spinal cord is affected and early symptoms of B12 deficiency are usually numbness and tingling in the arms and legs. Lack of energy and neurological problems usually occur before the anemia is detected.

The anemia associated with B12 deficiency is called megaloblastic anemia because blood cells become larger than normal. This happens because without B12 and folic acid DNA cannot form normally and this prevents the nucleus of blood cells from maturing. The body of the cell grows too large while waiting for the nucleus. This type of anemia can be corrected by taking folic acid, but only B12 supplements can stop the nerve damage.

People who eat cholesterol-free plant-based diets/vegans and wash their hands after using the toilet and don’t grow their own vegetables in night soil or take B12 supplements WILL get B12 deficiency. This is easily prevented by taking B12 supplements. People with chronic health problems such as GERD (gastroesophageal reflux disease) and diabetes should reconsider their food choices and also take B12 supplements. The Centers for Disease Control (CDC) and the Institute of Medicine recommend B12 supplements for everyone over 50 years old.

How much B12 do you need?

We lose 0.1% of our B12 stores in urine each day, the more stores we have the more we lose but when our stores are depleted we don’t lose any. Pregnant and lactating women also lose B12 stores through the placenta and in breast milk. The average adult who is able to absorb B12 has about 2 to 5 milligrams (mg) of stores. Losing 0.1% would be about 2 -5 mcg a day. The recommended daily intake for adults was set at 2.4 mcg in the 1950s, but given the changes in our food supply aiming for 4 to 7 mcg may be a better.  BUT if you are getting this much B12 from animal products, you are getting a lot of cholesterol and it is a safe bet that you have atherosclerosis. If you don’t have high blood pressure yet you will soon have it along with a heart attack or a stroke.

For example, many people eat beef liver to get B12. In the 1920s people with Pernicious Anemia were fed pounds of raw liver or liver juice every day. It worked because there was no IF and 1% of the free B12 that made it to the ileum was absorbed by passive diffusion.  Liver was also used to treat other anemias and as a result liver became firmly entrenched as a health food in the minds of our grandparents and parents. There are still some dietitians and health care providers today who advise their patients to eat lots of liver.

Industrial Chicken Coop (Public Domain)
Industrial Chicken Coop (Public Domain)

A 3 ½ oz (100 grams) serving of braised beef liver contains 70.6 mcg of B12. Only 60% (42.4 mcg) is bioavailable but that does not matter because you can only absorb an average of 1.75 mcg of this with IF at a time. Remember, if you have IF most of the B12 from food will attach to it, only a small amount will be free and 1% of the free B12 will be absorbed by passive diffusion.    Assuming 1/3 of the bioavailable amount is free (14.1 mcg) and you absorb 1% of that (0.14 mcg). 1.75 +.14 mcg = 1.99 mcg of B12. One serving of beef liver has 396 mg of cholesterol. In order to get 4 mcg of B12 you need 2 servings of liver = 792 mg cholesterol

If you don’t like liver and think chicken is a healthy food choice, a 100 g chicken breast (31/2 oz) has approximately 0.30 mcg of B12 and 93 mg of cholesterol. In order to get 4 mcg of B12 you will need about 12 servings of chicken which will give you 1116 mg cholesterol. Even “cholesterol deniers” will agree that this is a lot of cholesterol for a small amount of B12.  You really are better off getting B12 from supplements.

Some natural plant sources of B12 such as seaweeds get B12 from symbiotic bacteria that live on them. Other types of seaweed and algae such as spirulina are advertised as having B12 but they really have B12 analogues, substances that look like B12 but they do not work like B12. Some of the analogues actually compete with real B12 and may decrease B12 absorption. Some fermented foods may contain active B12 but the common ones such as miso and tempeh do not contain B12. Plants are NOT a reliable source of B12. Better be safe than sorry and get B12 from supplements or fortified foods.  Cholesterol-free dietary sources of B12 include fortified nutritional yeast, non-dairy milks, cereals and energy bars. Check labels carefully because not all cereals under the same brand contains B12.

I don’t sell supplements or recommend any particular brand of B12 but I prefer chewable or quick dissolve fruit flavored methylcobalamin tablets. Cyanocobalamin works well but it requires an extra detoxification step to get rid of the cyanide. Theoretically, sublingual tablets should be better because they skip the whole intestinal absorption process and send B12 directly to the blood through membranes under the tongue, but that has not been shown to be true. There is no significant difference between oral and sublingual B12for the treatment of B12 deficiency. Sublingual is usually more expensive so the best choice is oral methylcobalamin supplements.

In order to absorb 4 to 7 micrograms a day you have to take in at least 250 mcg of B12 a day.  A 500 mcg daily supplement will give you all you need. You can also take 2500 mcg B12 weekly.  If you have had abdominal surgery or have severe anemia you may need B12 injections but injections are not necessary for most people. B12 injections will correct B12 deficiency but it will NOT give you energy if you are not B12 deficient.

25 thoughts on “Do carnivores need Vitamin B12 supplements?

  • March 14, 2022 at 8:29 AM

    Informational and helpful content.

  • April 25, 2021 at 7:59 PM

    Could the sources of this article be referenced ? Thank you

  • April 2, 2021 at 9:54 AM

    This is really great! Thank you!

  • November 2, 2019 at 2:32 PM

    This article is bias. HUMAM ARE NOT HERBIVORES. We thrive on animal products. We get sick and deprived on plant based food. I know, I was. Eating meat (unprocessed) brought back my energy, healthy weight and no deficiency in vitamins, minerals and amino acids. And NO, no heart burns/ acid reflux eating whole food animal products. DO YOUR HOMEWORK.

  • October 14, 2019 at 9:31 AM

    According to Dr. Jennifer Rooke in an article in the Baltimore Post-examiner, 90% of the world’s B12 supplements are fed to livestock as well as being artificially added to dairy supplies. This is due to the unnatural diets that are fed to animals, who would traditionally get their B12 from grazing straight from the soil. Even for omnivores who get a decent meat-heavy diet, practitioners such as Dr. Greger recommends that we all take supplements of the vitamin because our bodies have such a hard time absorbing it — especially those over 50 years old.

  • May 12, 2019 at 1:00 PM

    GREAT ARTICLE. The human animals aren’t carnivore, omnivore, natural born killers, hunters. We are 100% HERBIVORE. HUMAN= peaceful, ethical, compassionate, moral, empathetic, honest, good natured, respectful and HUMANE. Before we foolishly chose to eat animal flesh, eggs, milk and other products we got everything we needed from plants. Ever since we choose to cheat ourselves with eating animal products we must sterilise everything.. even vegetables. Most people of course don’t realise that our food is coming from the ground and not from someone else’s stomach. As long as we continue eat, wear, use other animals we, the children, other species and our environment will suffer too.

  • March 6, 2019 at 5:19 PM

    I have about questions about the source of the “90% of b12” given to livestock statistic. Where did this figure come from?

  • March 6, 2019 at 5:19 PM

    I’d also like to know the source of the “90% of b12 given to livestock”. I’ve been searching for an original source but haven’t found it.

  • March 12, 2018 at 8:57 PM

    nice article

  • December 9, 2017 at 6:45 PM

    How are we supposed to take this article seriously when she doesn’t seem to know the difference between an omnivore and a carnivore? Humans are not carnivores.

    • December 11, 2017 at 9:21 PM

      The author may not have selected the title. I think that comes from the newspaper, not the author.

  • December 7, 2017 at 10:26 AM

    Seems like this would be a good reason to eat grass-fed beef and pasture-raised chickens, no?

    • October 30, 2016 at 4:25 PM

      I find this number too low. I found numbers in an official report in Austria and the livestock industry here needs about 57-60 tons a year. This was back in 2005. there are only about 750000 vegans / vegetarians here as this would mean 80grams B12/person/year if you use the remaining 10% for them. That a way too much. Even if you use 1000mcg a day for a year is not even a gram of B12 per year/person. All the numbers I posted are metric. Therefore 90% only for livestock is way too underestimated

  • July 4, 2016 at 11:27 PM

    “We are getting smarter about protein and many people now accept that plant foods are a healthier source of protein,”

    Bias shown in only the second sentence. Oh, I see. If I were “smart” I would accept that plant protein is healthier. Nothing of the sort has been proved by science. So far, just the opposite.

  • March 24, 2016 at 8:22 AM

    Very well written!

  • July 30, 2015 at 1:39 AM

    What nonsense! Our ancestors didn’t suddenly find themselves unable to produce B12 and decided to solve the problem by eating their own crap!

    Our ancestors gradually lost the ability to produce B12 because their animal-rich diet contained so much of the stuff that there was simply no need for it any more.

    Perhaps in a few thousand years, vegans will evolve huge bellies to house the quantity of guts needed to recover that ability. Either that or start eating their own crap.

    • August 14, 2016 at 10:44 AM

      You are incredibly mis-informed, wrong and blatantly stupid!

    • August 14, 2016 at 10:45 AM

      P.S the b12 you eat is from fecal matter inside the meat you consume. enjoy turd muncher 😉

    • November 2, 2016 at 1:21 PM

      Humans didn’t lose the ability to produce B12. We just started washing our hands (and power washing our vegetables) and stopped drinking well or river water (or at least started treating our water with chemicals to kill bacteria). Very early on, we stopped eating bugs too.

  • August 4, 2014 at 1:11 AM

    Excellent, highly informative piece on this subject, thank you so much, you’ve done a great service for this issue! I usually take methylcobalamin but now have some cyanocobalamin B12 and see that it’s okay to use but the former is slightly preferred. I’m not worried about the trace of cyanide, as I don’t smoke cigarettes or have other cyanide risk factors. I must share your article somehow 🙂

  • October 31, 2013 at 5:50 PM

    B12 now available in intra-cellular liposomal B12 is 100% available even after bypass. look for max health liposomal

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