August 21, 2017
Clinical Insights into Vitamin B12
Session Date: October 24, 2017
Session Presenter: Roman Pawlak, PhD, RD (East Carolina University)
Session Description: Once thought to be extremely rare and found only among some vegans, vitamin B12 deficiency is a worldwide problem. Hundreds of new publications describing new insights regarding the role of B12 status in disease development are published every year. Clinicians are not able to keep up with all of the new findings. This leads to holding on to old myths and assumptions and missing out on proper assessment of B12 status. Some key points included:
- Individuals at risk of inadequate B12 status include:
- all vegetarians and vegans
- older adults and elderly
- those taking Metformin
- those with gastrointestinal (GI) conditions/surgery
- The Institute of Medicine (IOM) set the Recommended Dietary Allowance (RDA) at 2.4 mcg/d in 1998 based on the amount needed for the maintenance of hematological status and normal serum B12.
- 9-month delay between hematological effects and signs of symptoms can be unfortunate for a growing fetus.
- Intake of 4-7 mcg/d in individuals with normal absorption is associated with adequate B12 status, which suggests the current RDA of 2.4 mcg might be inadequate for optimal biomarker status even in a healthy population between 18 and 50 years of age.
- Further research is needed to determine adequate amounts to compensate for daily B12 loss, which can range from 1.4 to 5.1 mcg/d.
- New research calls for an increase in RDA and creation of age-based recommendations.
- Holotranscobalamin II (holoTCII or TCII) and methylmalonic acid (MMA) are the best assessment tools.
- Mean Corpuscular Volume (MCV) is unreliable.
- Serum B12 and homocysteine (Hcy) are used most often in clinical settings.
- Studies have examined the relationship between plasma total Hcy and MMA to blood vitamin B12. Concentrations of these metabolic markers start to increase at B12 levels considerably above the typical cut-off value used to define B12-deficiency (148 pmol/L).
- B12 concentrations in serum reflect both intake and stores. The lower limit varies with the method used and the laboratory conducting the analysis.
- Hcy is a better marker than serum B12. Hcy has limitations; can be influenced by other non-nutritional and nutritional issues.
- Use at least two different biomarkers to obtain reliable B12
- Hemoglobin (Hb), serum ferritin and platelet count can be indicative of B12.
- Abnormally low Hb may be a result of B12 rather than iron deficiency.
- B12 is needed for synthesis of all blood cells; affects will be seen in platelet values.
- B12 status and hyperhomocysteinemia are associated with select health conditions: cardiovascular disease (CVD), organic mental disorders, osteoporosis/bone fractures, brain atrophy, diabetic comorbidities.
- Epidemiologic data linking Hcy with atherosclerosis is strong: each increase of 5 mmol/L in Hcy increases the risk of Coronary Heart Disease (CHD) event by approximately 20%, independent of traditional CHD risk factors.
- Vegetarians and vegans have higher levels of Hcy, and are at a higher risk for CVD, even when cholesterol and blood sugar are within normal levels.
- In patients with brain atrophy and high baseline omega-3 fatty acids (>590 umol/L), B vitamin treatment slowed the mean atrophy rate by 40.0%. B vitamin treatment had no significant effect on the rate of atrophy among subjects with low baseline omega-3 fatty acids (<390 umol/L).
- Meta-analysis of studies including 4,475 people showed a modest decrease in fracture risk of 4% per 50 pmol/L increase in B12.
- “B12 is more effective than nortriptyline for the treatment of symptomatic painful diabetic neuropathy.”
- Reliable B12 deficiency treatment options include B12 injections and B12 supplements.
- Nutritional yeast is effective only when fortified with B12, algal use is unreliable and probiotics made no difference.
Written by Samantha Abshire, a 2nd year MSN-DPD student at Bastyr University. She can be contacted at firstname.lastname@example.org.