October 2012 Issue

Boosting B12 Intake — More Experts Believe the Recommended Dietary Allowance Should Be Higher
By Linda Antinoro, RD, JD, LDN, CDE
Today’s Dietitian
Vol. 14 No. 10 P. 15

Is vitamin B12 the new darling of nutrients? The 2010 Dietary Guidelines included it as one of the nutrients in which supplementation may be warranted for older individuals. Because many people over the age of 50 lose the ability to absorb vitamin B12 from foods due to a decreased production of hydrochloric acid in the stomach, the guidelines recommend people in this age bracket consume a B12-containing supplement or B12-fortified foods because those sources don’t require stomach acid for absorption. The Recommended Dietary Allowance (RDA) is 2.4 mcg/day, but some nutrition experts are questioning whether that amount is enough.

Normal value ranges for vitamin B12 vary slightly among different laboratories and can range anywhere between 200 to 900 pg/mL. The general consensus is values less than 200 pg/mL constitute a B12 deficiency. Katherine Tucker, PhD, a professor of nutrition at Northeastern University in Boston, advocates that B12 adequacy is achieved with a serum level of at least 350 pg/mL.

“A level between 200 and 350 pg/mL may still be deficient for an individual,” Tucker says. “It may be best to follow up by testing for methylmalonic acid, a specific measure of B12 status that rises when the body has too little B12. If that’s elevated, it provides more evidence for B12 deficiency.” Research from Rush University Medical Center in Chicago supports Tucker’s stance.1

Christine Tangney, PhD, a researcher in a cognition and brain MRI study that measures methylmalonic acid, agrees that marginal B12 status in older age is frequently missed by the measurement of serum B12 levels alone. “Yet testing for methylmalonic acid may not be so realistic, as it’s very expensive and is also prone to false readings if kidney function is compromised,” she cautions.

Since screening for B12 status typically now relies mainly on serum B12 values, one potential solution is to aim for a higher serum B12 level within the normal range.

Vitamin B12 serves important roles throughout the body. It’s required for proper red blood cell formation, neurological function, and DNA synthesis. While neurological problems and certain anemias, such as megaloblastic and pernicious, are synonymous with B12 deficiency, other possible health consequences may arise due to inadequate levels. These include the following:

Cognitive impairment: Research has linked B12 and brain function over the years. In one randomized controlled trial, researchers investigated cognitive function in a group of 900 older adults divided into two groups. For two years, one group received daily oral supplements of 400 mcg of folic acid and 100 mcg of B12 along with the promotion of physical activity. The other group received placebo treatment. The supplemented group showed improvements in cognitive functioning, particularly immediate and delayed memory performance, compared with the group receiving placebo treatment.2

While declines in cognitive function can be a possible forerunner to Alzheimer’s disease, a direct link between vitamin B12 levels and this disease’s development is lacking. Yet a University of Oxford study shows that B12 levels at 417 pg/mL or less—above the cutoff for deficiency—were associated with a more rapid rate of brain atrophy.3 Since brain atrophy is associated with Alzheimer’s disease, it’s theorized that higher B12 levels may modify risk.

Depression: A cause-and-effect relationship between B12 and depression remains elusive, but an association between intake and incidence of depression has been shown. In one study, researchers found that among just over 3,500 older adults followed for up to 12 years, the risk of developing depression symptoms declined by 2% for every 10-mcg increase in B12 intake.4 People in the study consumed anywhere from 0.3 to 266 mcg/day. However, another study found B12 failed to benefit depressive symptoms.5 Individuals in this study received 20 mcg of B12.

Osteoporosis: In the Framingham Offspring Osteoporosis study of 2,567 men and women, those with low B12 levels (less than 200 pg/mL) had lower-than-average bone mineral density than those with vitamin B12 above this cutoff.6 Vitamin B12 is important for aiding osteoblasts and lowering blood levels of homocysteine, which may interfere with collagen cross-linking. Remedying B12 deficiency may be a factor in reducing osteoporosis risk.

Age-related macular degeneration (AMD): In the Women’s Antioxidant and Folic Acid Cardiovascular Study, 5,200 women received daily 2.5 mg of folic acid, 50 mg of vitamin B6, and 1,000 mcg of vitamin B12. After an average of seven years of treatment and follow-up, there was a 35% to 40% reduced risk of AMD.7 The researchers couldn’t say how much of this apparent benefit was due to B12.

Other research data relating B12 to AMD are limited. Yet because it has the potential to ward off this common eye condition among people aged 50 and older, it’s still another reason for ensuring adequate consumption of this vitamin.

Raising Requirements
Many experts believe the current RDA for vitamin B12 is too low. Data suggests daily intake between 6 and 10 mcg better ensures acceptable B12 concentrations in people with adequate vitamin B12 status and absorption.8 Those taking various medications, namely metformin; proton-pump inhibitors, such as Prilosec; or H2 receptor antagonists, such as Pepcid, may need more vitamin B12 due to these drugs’ ability to interfere with B12 absorption.

“I recommend the use of supplements with between 500 to 1,000 mcg a day for people with serum levels less than 350 pg/mL,” Tucker says. “The need for such a high amount is that only a small proportion of the B12 from a supplement pill gets absorbed.”

In addition, there’s no Tolerable Upper Intake Level set for this vitamin, so toxicity isn’t a concern. Only those individuals with Leber’s disease, a hereditary eye condition, shouldn’t take supplemental B12.

Synthetic B12 found in supplements and fortified foods appears to be the best form. Though naturally occurring B12 is present in protein foods of animal origin, it may not be equal in its effectiveness in raising serum B12 levels. In a large population-based study, total intake of B12—particularly from milk and fish—were better than meat and eggs in increasing blood levels.8 Dairy foods especially appear to provide a highly bioavailable source of the vitamin. Vitamin B12 in meat may be less bioavailable due to losses during cooking and the presence of collagen, which isn’t digested as well with decreased gastric secretion.

Bottom Line
When counseling clients regarding their vitamin B12 status, advise anyone with a blood level less than 350 pg/mL to take a B12 supplement or, at the very least, a multivitamin formulated for individuals over the age of 50. For all others, encourage them to eat routinely B12-containing foods, including at least some B12-fortified foods.

— Linda Antinoro, RD, JD, LDN, CDE, is part of the nutrition consultation service at Brigham and Women’s Hospital in Boston.


1. Tangney CC, Aggarwal NT, Li H, et al. Vitamin B12, cognition, and brain MRI measures: a cross-sectional examination. Neurology. 2011;77(13):1276-1282.

2. Walker JG, Batterham PJ, Mackinnon AJ, et al. Oral folic acid and vitamin B-12 supplementation to prevent cognitive decline in community-dwelling older adults with depressive symptoms — the Beyond Ageing Project: a randomized controlled trial. Am J Clin Nutr. 2012;95(1):194-203.

3. Vogiatzoglou A, Refsum H, Johnson C, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly. Neurology. 2008;71(11):826-832.

4. Skarupski KA, Tangney C, Li H, Ouyang B, Evans DA, Morris MC. Longitudinal association of vitamin B-6, folate, and vitamin B-12 with depressive symptoms among older adults over time. Am J Clin Nutr. 2010;92(2):330-335.

5. Andreeva VA, Galan P, Torrès M, Julia C, Hercberg S, Kesse-Guyot E. Supplementation with B vitamins or n-3 fatty acids and depressive symptoms in cardiovascular disease survivors: ancillary findings from the SUpplementation with FOLate, vitamins B-6 and B-12 and/or OMega-3 fatty acids (SU.FOL.OM3) randomized trial. Am J Clin Nutr. 2012;96(1):208-214.

6. Tucker KL, Hannan MT, Qiao N, et al. Low plasma vitamin B12 is associated with lower BMD: the Framingham Osteoporosis Study. J Bone Miner Res. 2005;20(1):152-158.

7. Christen WG, Glynn RJ, Chew EY, Albert CM, Manson JE. Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women: the Women’s Antioxidant and Folic Acid Cardiovascular Study. Arch Intern Med. 2009;169(4):335-341.

8. Vogiatzoglou A, Smith AD, Nurk E, et al. Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study. Am J Clin Nutr. 2009;89(4):1078-1087.


Vitamin B12 Sources


Amount (mcg)

Multivitamin (eg, One A Day Men’s/Women’s 50+ Healthy Advantage), 1 pill*


Odwalla Superfood Blueberry Bsmoothie, 8 oz*


Fortified breakfast cereal (eg, Total), 3/4 cup*


Salmon, wild, cooked, 3 oz


Silk soymilk, 8 oz*


Tuna, light, canned in water, 3 oz


Cottage cheese, 1% low fat, 1 cup


Beef, tenderloin, cooked, 3 oz


Milk, nonfat, 8 oz


Egg, 1 medium


*Source of synthetic B12
Sources: Product labels; USDA National Nutrient Database for Standard Reference, Release 24