Many people are susceptible to a vitamin B-12 deficiency and need to take supplements to obtain this nutrient. Shellfish is among the leading dietary sources of vitamin B-12. If you have a shellfish allergy, you may be concerned about potential allergic reactions when taking nutritional supplements containing vitamin B-12. However, shellfish is not the source of vitamin B-12 in supplements. Consult your doctor about fulfilling your vitamin B-12 requirements if you have a shellfish allergy.
Vitamin B-12
Vitamin B-12 is a water-soluble vitamin that is vital for nerve cell function, synthesis of DNA and production of red blood cells. The vitamin contains a metal ion called cobalt and is the largest vitamin. Yet your body requires minute amounts of this nutrient. The recommended daily allowance is 2.4 micrograms for adults 19 years and older. Vegetarians, the elderly and people with intestinal absorption problems are susceptible to vitamin B-12 deficiencies that can increase your risk of nervous system dysfunction and megaloblastic anemia, a condition characterized by an insufficient number of red blood cells that are larger than normal.
Dietary Sources
Vitamin B-12 is found in animal products including shellfish, fin fish, meat and dairy. Clams, mussels and oysters have the highest concentrations of vitamin B-12. Octopus, crab and lobster also contain high amounts of vitamin B-12 compared with most other types of animal products. Vegetarians do not eat these foods and must take supplements to obtain the nutrient. Nonetheless, the source of vitamin B-12 in supplements is from bacteria and not from shellfish.
Shellfish Allergy
When you have a shellfish allergy, you may be allergic to all types of shellfish or just certain types of shellfish. A shellfish allergy causes an allergic reaction, such as hives, nasal congestion, wheezing, abdominal pain, dizziness or anaphylaxis, when you eat shellfish. Anaphylaxis is a life-threatening allergic reaction characterized by airway constriction, rapid pulse, shock and lightheadedness. Exposure to a small amount of shellfish can cause an allergic reaction. Skin and blood tests can confirm if you have an allergy to shellfish.
Considerations
If the manufacturing facility or other ingredients in the vitamin B-12 supplement contain substances from shellfish, such as glucosamine sulfate, it is possible you can have an allergic reaction. Some sources of glucosamine sulfate products are made from the shells of crabs, shrimp or lobsters, but allergic reactions to shellfish are typically caused by the meat, not the shell. As of date of publication, there are not any reports of allergic reactions to glucosamine in people with an allergy to shellfish. In addition, there is evidence people with shellfish allergy can safely take glucosamine products.
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