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Charles Vlasov
Charles Vlasov

Where Can I Buy Vitamin B12

Intake recommendations for vitamin B12 and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine [1]. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include:

where can i buy vitamin b12

Table 1 lists the current RDAs for vitamin B12 [1]. For adults, the main criterion that the FNB used to establish the RDAs was the amount needed to maintain a healthy hematological status and serum vitamin B12 levels. For infants aged 0 to 12 months, the FNB established an AI that is equivalent to the mean intake of vitamin B12 in healthy, breastfed infants.

FoodVitamin B12 is naturally present in foods of animal origin, including fish, meat, poultry, eggs, and dairy products [5]. In addition, fortified breakfast cereals and fortified nutritional yeasts are readily available sources of vitamin B12 that have high bioavailability [12,13].

The average vitamin B12 level in the breast milk of women with vitamin B12 intakes above the RDA is 0.44 mcg/L [14]. The U.S. Food and Drug Administration specifies that infant formulas sold in the United States must provide at least 0.15 mcg vitamin B12 per 100 kcal [15].

In addition to oral dietary supplements, vitamin B12 is available in sublingual preparations as tablets or lozenges [22]. Evidence suggests no difference in efficacy between oral and sublingual forms [25,26].

Prescription medicationsVitamin B12, in the forms of cyanocobalamin and hydroxycobalamin, can be administered parenterally as a prescription medication, usually by intramuscular injection [2]. Parenteral administration is typically used to treat vitamin B12 deficiency caused by pernicious anemia as well as other conditions (e.g., tropical sprue, pancreatic insufficiency) that result in vitamin B12 malabsorption and severe vitamin B12 deficiency [5].

Vitamin B12 is also available as a prescription nasal gel spray. This formulation appears to be effective in raising vitamin B12 blood levels in adults and children [27,28]. A small clinical study with 10 participants (mean age 81 years) found that the bioavailability of a 1,000 mcg cobalamin dose was 2% with intranasal administration, which is similar to the bioavailability of an oral dose [29].

Causes of vitamin B12 deficiency include difficulty absorbing vitamin B12 from food, lack of intrinsic factor (e.g., because of pernicious anemia), surgery in the gastrointestinal tract, prolonged use of certain medications (e.g., metformin or proton pump inhibitors, discussed in more detail below in the section on interactions with medications), and dietary deficiency [5,7]. Because people who have difficulty absorbing vitamin B12 from food absorb free vitamin B12 normally, their vitamin B12 deficiency tends to be less severe than that of individuals with pernicious anemia, who cannot absorb either food-bound or free vitamin B12. Certain congenital conditions, such as hereditary intrinsic factor defects and congenital vitamin B12 malabsorption (Imerslund-Gräsbeck disease), can also cause severe vitamin B12 deficiency [5].

The effects of vitamin B12 deficiency can include the hallmark megaloblastic anemia (characterized by large, abnormally nucleated red blood cells) as well as low counts of white and red blood cells, platelets, or a combination; glossitis of the tongue; fatigue; palpitations; pale skin; dementia; weight loss; and infertility [2,5,7]. Neurological changes, such as numbness and tingling in the hands and feet, can also occur [7]. These neurological symptoms can occur without anemia, so early diagnosis and intervention is important to avoid irreversible damage [35]. In addition, some studies have found associations between vitamin B12 deficiency or low vitamin B12 intakes and depression [36-38]. In pregnant and breastfeeding women, vitamin B12 deficiency might cause neural tube defects, developmental delays, failure to thrive, and anemia in offspring [7].

Because the body stores about 1 to 5 mg vitamin B12 (or about 1,000 to 2,000 times as much as the amount typically consumed in a day), the symptoms of vitamin B12 deficiency can take several years to appear [7,33].

Older adultsDepending on the definition used, between 3% and 43% of community-dwelling older adults, especially those with atrophic gastritis, have vitamin B12 deficiency based on serum vitamin B12 levels [41,42]. The deficiency rate at a cutoff of less than 211 mcg/L (156 pmol/L) at admission to a long-term care facility, according to one study, was 14%, and 38% of these older adults had levels lower than 407 pg/mL (300 pmol/L) [42].

Individuals with pernicious anemiaPernicious anemia is an irreversible autoimmune disease that affects the gastric mucosa and results in gastric atrophy [1,46]. This disease leads to attacks on parietal cells in the stomach, resulting in failure to produce intrinsic factor and malabsorption of dietary vitamin B12, recycled biliary vitamin B12, and free vitamin B12 [1,6,11].Therefore, without treatment, pernicious anemia causes vitamin B12 deficiency, even in the presence of adequate vitamin B12 intakes.

Pernicious anemia is the most common cause of clinically evident vitamin B12 deficiency around the world [11,46]. The incidence of pernicious anemia in the United States is an estimated 151 per 100,000, and this condition is more common in women and in people of European ancestry [46].

Individuals who have had gastrointestinal surgerySurgical procedures in the gastrointestinal tract, such as for weight loss or to remove all or part of the stomach, can cause a complete or partial loss of cells that secrete hydrochloric acid and cells that secrete intrinsic factor [52,53]. Thus, these procedures reduce the amount of vitamin B12, particularly food-bound vitamin B12, that the body absorbs [52,53]. High doses (1,000 mcg/day) of oral methylcobalamin supplements appear to be as effective as hydroxycobalamin injections in normalizing vitamin B12 values in patients who have undergone Roux-en-Y gastric bypass surgery [54].

VegetariansVegans who consume no animal products and vegetarians who consume some animal products (e.g., dairy products, eggs, or both) but not meat have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods [3,55]. Consumption of foods fortified with vitamin B12 (such as fortified nutritional yeasts) as well as vitamin B12 supplements can substantially reduce the risk of deficiency [55].

CancerThe evidence for a relationship between vitamin B12 and cancer risk is mixed. Some evidence supports a link between increased cancer risk and higher intakes or blood concentrations of vitamin B12, some supports a link with lower intakes or concentrations, and some evidence indicates no link at all.

Some observational evidence also shows an association between supplements containing vitamin B12 and a higher risk of certain types of cancer. For example, an assessment of 77,118 participants aged 50 to 76 years in the Vitamins and Lifestyle cohort study found that use of at least 55 mcg/day supplemental vitamin B12 for an average of 10 years was associated with a 40% higher risk of lung cancer in men [60]. However, the study found no association between supplemental vitamin B12 use and cancer risk in women.

Limited clinical trial evidence supports the finding that higher vitamin B12 intakes might increase cancer risk. In an analysis of data on 2,524 participants in the B Vitamins for the Prevention of Osteoporotic Fractures trial who were treated with supplements containing 400 mcg/day folic acid and 500 mcg/day vitamin B12 for 2 to 3 years, the risk of colorectal cancer was significantly higher, at 3.4%, in the supplementation group than in the placebo group, whose rate was 2% [61]. However, high folic acid levels are potentially linked to increased risk of colorectal cancer, so the result might be due to the folic acid rather than the vitamin B12 [62]. Furthermore, the supplements had no significant effect on overall cancer risk.

Some observational evidence shows no association between high vitamin B12 concentrations or intakes and increased risk of certain cancers. For example, higher vitamin B12 intakes or serum concentrations were not associated with an increased risk of pancreatic cancer [63], breast cancer [64], or esophageal cancer or gastric cancer [65]. Clinical trials support the lack of association between higher vitamin B12 intakes and cancer risk. [66-68]. For example, a meta-analysis of 18 RCTs that included 74,498 individuals found that supplements containing B vitamins, including 20 to 2,000 mcg/day vitamin B12, had little or no effect on cancer incidence, cancer deaths, or all-cause mortality during follow-up periods of 2 to 7.3 years [68].

Finally, evidence pointing to an association between lower vitamin B12 levels and a higher cancer risk includes observational data showing a risk of gastric cancer that was 5.8 times higher in male smokers with lower vitamin B12 levels (less than 394 pg/mL [291 pmol/L]) than in those with levels higher than 591 pg/mL (436 pmol/L) [69]. Also, two meta-analyses found associations between lower vitamin B12 concentrations or intakes and a higher risk of colorectal cancer [70] and prostate cancer [71].

Cardiovascular disease and strokeAn elevated homocysteine level has been associated with an increased risk of CVD [72,73]. Vitamin B12 and other B vitamins are involved in homocysteine metabolism, and researchers have hypothesized that supplementation with these micronutrients can reduce CVD risk by lowering homocysteine levels [72,73].

RCTs have found that vitamin B12 (and folic acid) supplements lower homocysteine levels, but not CVD risk. The authors of a Cochrane review of the effects of homocysteine-lowering interventions on cardiovascular events based on 15 studies in 71,422 participants concluded that supplements of vitamin B12 alone or with other B vitamins do not prevent heart attacks or reduce death rates in people at risk of or with CVD [76]. More recently, an extended follow-up of the B-PROOF trial, (which compared 400 mcg folic acid and 500 mcg vitamin B-12 daily with placebo) in 1,298 participants found that after a median of 54 months, the intervention had no effect on CVD risk [77]. 041b061a72


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