Vitamin B-12 is a crucial vitamin needed for normal physiology. The symptoms of B-12 deficiency are insidious and can easily go unnoticed for a long period of time. That’s why it’s so important that you are aware of the deficiency signs and also what you can do to ensure sufficient intake.
Did you know that…?
- 50% of long time vegetarians and 80% of vegans are deficient in this vitamin
- It’s possible to follow a paleo lifestyle and still be deficient in B-12
- B-12 deficiency can be a cause of infertility
- Some drugs, like metformin deplete B-12 in the body
- Stomach acid is required to make B-12 active. PPIs and other acid suppressing drugs
- People with Crohn, UC, and IBS are at risk of deficiency
The Basic Biochemistry:
Vitamin B-12 absorption is highly reliant on normal digestive function. Intrinsic factor (produced in the stomach) is necessary to make B-12 active. Intrinsic factor cleaves off a protein complex from B-12 and then it binds itself to B-12. At this point B-12 travels down the digestive tract to the small intestine where it can be transported in the blood.
B-12 Effects in the Body:
Vitamin B-12 is so necessary for our health, because it is a co-factor needed for many biochemical reactions, and it is a different kind of nutrient, because it is what we term a ‘methylator’. As a methylator, B-12 removes methyl groups from methyltetrahydrofolate to THF. This makes folate “active”, and active folate is needed to synthesize DNA. B-12 also transfers a methyl group from the harmful substance, homocysteine to methionine. Methionine is needed to form the myelin sheaths of nerves. B-12 is also involved in metabolizing carbohydrates. The nervous system relies on carbohydrates for fuel. A deficiency of B-12 can be a direct cause of many neurological problems.
Signs of B-12 deficiency include:
- Fatigue
- Depression
- Peripheral neuropathy
- Anemia
- Confusion
- Memory loss
- Digestive problems due to lack of stomach acid
- Decreased immune response
Sources of B-12 and its Bioavailability:
It is crucial to get enough vitamin B-12 from food. The RDA for B-12 is 3 mcg. Many people mistakenly believe that their diet supplies sufficient B-12 based on this estimated daily requirement. An optimal intake, which promotes health and prevents disease, is actually much higher at 100-500 mcg.
Animal sources are far and away the most nutritive sources of B-12. There is much debate over non-animal sources of B-12. The truth is that it is difficult if not impossible to attain sufficient levels from only non-animal sources. First, non-animal sources are far less concentrated. Second, many of the touted vegan sources of B-12 actually contain B-12 analogues instead of a form that is actually useful to the body. The tricky thing is B-12 analogues show up on lab tests, but they do not have the activity of real B-12. This means it’s critical that vegans and vegetarians supplement B-12.
Furthermore, current research shows that many people genetically have a MTHFR mutation, which prevents them from achieving methylated reactions on their own. Their bodies absolutely require the methylated/active form of B-12 only.
Food Sources of Vitamin B-12 include:
| Animal food | Amount | mcg of B12 | Non-animal food | Amt | mcg of B12 |
| Liver, beef | 3 oz | 93.5 | Brewer’s yeast | 2 Tbsp | 2.0 |
| Clams | 3 oz | 60.0 | Nori | 2 sheets | 2.0 |
| Salmon | 3 oz | 3.0 | Wakame | 3 wet oz | 1.9-5.3 |
| Lamb | 3 oz | 2.6 | Kombu | 3 wet oz | 1.5-4.1 |
| Lobster | 3 oz | 2.6 | Arame | 3 wet oz | 0.09-0.15 |
| Beef | 3 oz | 2.0 | “Super Blue Green” algae | 3 g | 23.1 |
| Tuna | 3 oz | 1.8 | Chlorella | 3 g | 4.0 |
| Cheese | 3 oz | 1-2 | |||
| Milk (whole or skim) | 8 oz | 0.9 | |||
| Halibut | 3 oz | 0.8 | |||
| Egg | 1 large | 0.6 | |||
| Chicken | 3 oz | 0.3 |
*USDA Handbook #8 Series Washington DC, ARS, USDA, 1976-1986
Despite the concentration of B12 available in animal sources, people following omnivore (and even paleo) diets can and often are deficient in B12 also. How can this be? Mostly, this is because many people have problems with digestive absorption. Optimal absorption requires adequate stomach acid and intact intestinal brush borders. Digestive diseases such as crohn and ulcerative colitis can cause injury to the intestinal barriers. Functional problems can impair absorption too. These functional imbalances are much harder to catch, because they don’t show up with overt symptoms. Unfortunately, the symptoms of B-12 deficiency occur in stages with a slow progression. Ultimately, B-12 deficiency can cause irreversible nerve damage.
Why does B-12 deficiency go under the radar?
First of all, most physicians don’t test for vitamin deficiencies at all. If they consider B-12, they run a CBC to look at your blood cells. The problem is that it is the final stage of deficiency that will actually result in a change in your red blood cells (megaloblastic anemia). If your physician does test for B-12 specifically, he/she might order a serum test. It was discussed above that this test is not reliable and will report B12 analogues. Serum tests have reported that 52% of vegans and 7% of vegetarians are B-12 deficient. More sensitive testing, however, reports deficiency in 68% of vegetarians and 83% of vegans.
©2019 Copyright Dr. Ariel Touchet