Your body needs vitamin B12. Two of its important roles are making red blood cells and making DNA. The vitamin also helps keep your nerve cells healthy. Although your vitamin B12 levels are mostly determined by the foods you eat, your genes may also play a small role. An AncestryDNA^® Traits test can tell you if people with DNA like yours tend to have typical levels of vitamin B12.

Foods Rich in Vitamin B12

Unlike other vitamins such as vitamin C (found in a number of fruits and vegetables) and vitamin E (found particularly in nuts, seeds, and vegetable oils), vitamin B12 does not naturally occur in most food from plants.

Plant-based foods that do contain vitamin B12, such as fortified breakfast cereals and plant-based milks, have had the vitamin added by manufacturers.

Foods from animals, on the other hand, do naturally contain vitamin B12. Beef liver and clams, in particular, are excellent sources of nutrition for anyone who eats meat and is looking for foods with vitamin B12 in their diet.

Foods which are good sources of vitamin B12 include:

• Red meat
• Fish (such as tuna, salmon, and trout)
• Shellfish (such as clams)
• Dairy products (such as milk, cheese, and yogurt)
• Some fortified breakfast cereals
• Poultry
• Eggs
• Liver (such as beef liver)
• Enriched plant-based milk (such as soy or rice milk)
• Fortified nutritional yeast (a common B12 supplement for vegetarians/vegans)

Genetics and Other Factors Impacting Vitamin B12 Levels

In healthy individuals, diet is the biggest factor in determining vitamin B12 levels. But diet alone doesn’t determine how much vitamin B12 is in your body. Your genes can also, to an extent, affect your vitamin B12 levels.

The AncestryDNA^® test looks at DNA differences in 13 genes that may affect how well your body absorbs and uses vitamin B12. Some differences could cause you to retain less of the nutrient.

These DNA differences might cause a tendency toward slightly lower levels of vitamin B12 than average. But they won’t necessarily cause a vitamin deficiency, as there are other non-genetic factors that impact how well you absorb the vitamin.

People who are more likely to have low levels of vitamin B12 include the following:

• Older adults
• Vegans and vegetarians
• People with inadequate stomach acid
• People regularly on certain medications that interfere with the absorption of B12, such as some heartburn medicines
• Those with the blood disorder pernicious anemia
• People who have difficulty absorbing the vitamin through their small intestine, either due to surgical bowel removal or diseases such as celiac disease or Crohn’s which affect the absorption of nutrients in the digestive tract.

Vitamin B12 Deficiency

The daily amount of vitamin B12 you need depends on your age, but the recommended daily allowance (RDA) for the average adult is 2.4 micrograms (mcg). Pregnant women need a bit more (2.6 mcg), as do breastfeeding mothers (2.8 mcg).

Most people in the U.S. get enough vitamin B12 in a balanced diet. For example, you get about half of your RDA of vitamin B12 from eating two to three eggs. While some groups, such as older adults, may tend to have lower levels, a significant deficiency in vitamin B12, with classic signs and symptoms, is not very common in the U.S.

Some of the symptoms of a severe deficiency in vitamin B12 can include:

• Muscle weakness and fatigue
• Numbness or tingling sensations in the hands and feet
• Difficulty walking (trouble with balance and coordination)
• A smooth, inflamed tongue
• Pale or yellowish skin
• Loss or decrease of appetite, weight loss
• Mood or behavioral changes (such as irritability, depression)
• Memory loss and confusion (dementia)
• A sensation of an increased heart rate (heart palpitations)
• Lightheadedness and shortness of breath
• Anemia

Interesting Facts About Vitamin B12

Vitamin B12 is one of eight types of B vitamins, not twelve as the name might suggest. The eight types of vitamin B are:

• Thiamin (vitamin B1)
• Riboflavin (vitamin B2)
• Niacin (vitamin B3)
• Pantothenic acid (vitamin B5)
• Vitamin B6
• Biotin (vitamin B7)
• Folate (vitamin B9)
• Vitamin B12

These eight types of vitamin B, plus vitamin C are all water-soluble. This means they dissolve in water and are excreted by the body in urine daily, rather than being stored in fat and liver tissue, like fat-soluble vitamins, such as vitamin D.

Interestingly, vitamin B12 is the only water-soluble vitamin that your body is able to store for use later. In fact, your body is able to store 1,000 to 2,000 times as much vitamin B12 as you’d typically eat in a day, mainly in the liver.

So even if your body stops properly absorbing vitamin B12—due to factors such as diet changes, new health conditions, or advancing age—the symptoms of a deficiency in vitamin B12 could take years to appear.

References

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Johnson, Larry E. “Vitamin B12 Deficiency.” Merck Manual, November 2020. https://www.merckmanuals.com/home/disorders-of-nutrition/vitamins/vitamin-b12-deficiency

Oh, Robert C., and David L. Brown. “Vitamin b12 Deficiency.” American Family Physician, March 1, 2003. https://www.aafp.org/afp/2003/0301/p979.html.

“Vitamin B-12.” Mayo Clinic, July 17, 2021. https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663.

“Vitamin B-12.” NIH Office of Dietary Supplements. Accessed September 8, 2021. https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/.

“Vitamin B12.” Harvard T. H. Chan School of Public Health. Accessed September 8, 2021. https://www.hsph.harvard.edu/nutritionsource/vitamin-b12/.

“Vitamin B12.” NIH Office of Dietary Supplements. Accessed September 8, 2021. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/.

“Vitamin B12: What to Know.” Nourish by WebMD. Accessed September 8, 2021. https://www.webmd.com/diet/vitamin-b12-deficiency-symptoms-causes#1.

Watanabe, Fumio, Yukinori Yabuta, Tomohiro Bito, and Fei Teng. “Vitamin B12-Containing Plant Food Sources for Vegetarians.” Nutrients 6, no. 5 (2014): 1861–73. https://doi.org/10.3390/nu6051861.

“Water-Soluble vs. Fat-Soluble Vitamins.” WebMD. Accessed September 8, 2021. https://www.webmd.com/vitamins-and-supplements/fat-soluble-vitamins-vs-water-soluble-vitamins.