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Vitamin B12 Deficiency in Resettled Bhutanese Refugees
Abstract & Commentary
By Michele Barry, MD, FACP, and Brian G. Blackburn, MD
Dr. Barry is Senior Associate Dean for Global Health at Stanford University School of Medicine; Dr. Blackburn is a Clinical Assistant Professor in the Division of Infectious Diseases and Geographic Medicine at Stanford University School of Medicine.
Dr. Barry is a retained consultant for the Ford Foundation and has received research or grant support from Johnson & Johnson Corporate Foundation, the Doris Duke Foundation, and the National Institutes of Health. Blackburn reports no financial relationship to this field of study.
Synopsis: A recent survey detected vitamin B12 deficiency in 64% of Bhutanese refugees living in Nepali refugee camps. Post-resettlement sera drawn in the United States confirmed a vitamin B12 deficiency prevalence of 27%-32%. Any Bhutanese immigrant to the United States should be screened for B12 deficiency, megaloblastic anemia, and neurologic symptoms. Vitamin B12 supplementation and nutritional advice also should be offered.
Source: Vitamin B12 Deficiency in resettled Bhutanese refugees United States, 2008-2011. MMWR Morb Mortal Wkly Rep 2011;60:343-346.
Approximately 108,000 ethnic Nepalese people were forced to move from their long-standing homes in Bhutan in the 1990s and have since been living within refugee camps in Nepal. Since 2008, approximately 30,000 Bhutanese refugees have resettled in the United States, and more are expected to follow. Routine medical examinations of some of these resettled refugees revealed neurologic and hematologic abnormalities consistent with vitamin B12 deficiency, even in young adults. These cases prompted a Centers for Disease Control and Prevention (CDC) investigation of stored sera from overseas medical examinations that had occurred during 2007-2008, and post-arrival examinations that took place in three state health departments (Minnesota, Utah, and Texas) during 2010-2011. Records from a health clinic in St. Paul, MN, also were reviewed, to ascertain whether megaloblastic anemia or peripheral neuropathy were common findings in this refugee population.
Vitamin B12 deficiency was defined as a serum vitamin B12 concentration < 203 pg/ml. Low serum levels were found in 64% (63 of 99) of the specimens obtained from Bhutanese refugees living in Nepali camps during 2007-2008 (see Table 1, below). The prevalence of serum B12 deficiency subsequently was assessed in serum samples of Bhutanese and other refugees, collected during post-arrival medical screening examinations in Minnesota, Utah, and Texas during 2010-2011 (see Table 2, below).
Table 1. Vitamin B12 deficiency in adult Bhutanese refugees undergoing overseas medical screening examinations, by age group and sex Nepal, 2007-2008.
|B12 < 203 pg/mL*|
|Age group (years)|
* Serum total vitamin B12 was measured at CDC using the Roche E-170 automated electrochemiluminescence immunoassay.
Source: Centers for Disease Control and Prevention Migrant Serum Bank
Adapted from: Centers for Disease Control and Prevention. Vitamin B12 deficiency in resettled Bhutanese refugeesUnited States, 2008-2011. MMWR Morb Mortal Wkly Rep 2011;60:343-346.
Table 2. Proportion of refugees with vitamin B12 deficiency in post-arrival serum samples Minnesota, Utah, and Texas September 2010-January 2011.
|Characteristic||B12 < 203 pg/mL||B12 pg/mL|
|Democratic Republic of the Congo||0/1||||413||(413-413)|
|Adapted from: Centers for Disease Control and Prevention. Vitamin B12 deficiency in resettled Bhutanese refugees United States, 2008-2011. MMWR Morb Mortal Wkly Rep 2011;60:343-346.|
Of refugees from 12 countries, only refugees from Bhutan (27%) and Somalia (12%) showed any significant B12 deficiency prevalence rates. The lower B12 deficiency rates seen in resettled Bhutanese refugees compared to those found in refugee camps might have been due to the higher proportion of children < 15 years of age tested in the domestic samples from resettled refugees. It takes approximately 5-10 years for body stores of vitamin B12 to become depleted. Macrocytosis, anemia, and peripheral neuropathy were observed in 10%-20% of refugees upon review of St. Paul (MN) health clinic charts. H. pylori infection, often a cause of chronic gastritis, and, in turn, vitamin B12 deficiency, was more prevalent among those with B12 deficiency than among those without deficiency in a small cohort, although inadequate dietary intake was felt to be the more likely cause of B12 deficiency. Further investigation is ongoing to determine the prevalence of other micronutrient deficiencies in this population.
Vitamin B12, or cobalamin, is obtained naturally, but only from foods of animal origin including meat, eggs, and dairy products. Vitamin B12 deficiency leads to delayed DNA synthesis, resulting in megaloblastic anemia, peripheral neuropathy, and subacute combined degeneration of the spinal cord, as well as neuropsychiatric symptoms.1,2 The deficiency can be caused by an inherited or acquired lack of intrinsic factor required for absorption of B12, and is commonly known as pernicious anemia, but in the developing world, it is often caused by low dietary intake or food/cobalamin malabsorption. At times, this malabsorption of cobalamin is associated with atrophic gastritis and with H. pylori infection.1
Bhutanese refugees living in the Nepal refugee camps have had their rations provided by the World Food Programme and the United Nations High Commissioner for Refugees and they consist of rice, lentils, chickpeas, vegetable oil, sugar, salt, and fresh vegetables.1 Only certain refugees, including young, malnourished, pregnant, or lactating women are given multivitamin supplements. A locally made, fortified, blended food containing B12 and micronutrients is available, but is probably not being consumed likely demonstrated by the results observed in this study, emphasizing how a culturally sensitive approach to food supplementation is imperative.
This excellent investigation should alert all physicians caring for Bhutanese or Nepalese immigrants to screen for B12 deficiency, both clinically and serologically. Moreover, the investigators strongly suggest that all refugees be provided with 30 days of oral B12 supplementation (500-1000 µg daily), as subclinical deficiencies may be present despite normal levels of B12. Any refugee exhibiting B12 deficiency should be screened for H. pylori infection and given antibiotic treatment if needed. Clinicians should consider the possibility of other nutritional deficiencies in this population as well. Lastly, one should think about offering all Bhutanese refugees nutritional advice that emphasizes culturally acceptably food containing B12.