No está claro cuán grande es el papel de los antibióticos https://antibioticos-wiki.es en las relaciones competitivas entre los microorganismos en condiciones naturales. Zelman Waxman creía que este papel era mínimo, los antibióticos no se forman sino en culturas limpias en entornos ricos. Posteriormente, sin embargo, se descubrió que en muchos productos, la actividad de síntesis de antibióticos aumenta en presencia de otros tipos o productos específicos de su metabolismo.
Microsoft word - vitamin b-12.doc
Do You Need to Take a Vitamin B12 Supplement?
Last month’s Nutrition article highlighted older adults’ challenges for getting the nutrients that their bodies need. One suchnutrient is vitamin B12; in fact, an article by the USDA Human Nutrition Research on Aging, Tufts University, states that “asupplement containing…vitamin B12 or specific foods fortified with [vitamin B12] may be needed” by older adults.
Vitamin B12 is naturally present in some foods, added to others, and available as a dietary supplement and a prescriptionmedication. Vitamin B12 is needed to make red blood cells and DNA, and helps keep your nervous system workingproperly. Vitamin B12 deficiency can lead to fatigue, weakness, constipation, and loss of appetite. Neurological changes,such as numbness/tingling in the hands and feet, difficulty maintaining balance, and poor memory, can also occur.
Older Adults are at Risk of Vitamin B12 Deficiency
Most children and adults in the United States consume recommended amounts of vitamin B12 in their diet. However,some people—particularly older adults and those with reduced levels of stomach acidity—have difficulty absorbing vitaminB12 from food and, in some cases, oral supplements.
Atrophic gastritis, a condition affecting 10%–30% of older adults, decreases secretion of acid in the stomach. Individuals
with atrophic gastritis are unable to absorb the vitamin B12 that is naturally present in food. Most, however, can absorb
the synthetic vitamin B12 in fortified foods and dietary supplements. As a result, the Institute of Medicine recommends
that adults older than 50 years obtain most of their vitamin B12 from vitamin supplements or fortified foods
Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12is generally not present in plant foods, but fortified breakfast cereals are a readily available source of vitamin B12.
Fortified foods vary in formulation, so read product labels to determine which added nutrients they contain.
Dietary Supplements & Prescription Medications
Over-the-counter multivitamins do not contain enough vitamin B12 to raise a low blood level
. Specific vitamin B12
pills are required to assure that you get an adequate amount. Existing evidence does not suggest any differences among
oral supplements in terms of absorption or bioavailability. However the body’s ability to absorb vitamin B12 from oral
supplements is largely limited by other factors related to digestion. For example, only about 10 mcg of a 500 mcg oral
supplement is actually absorbed in healthy people.
Vitamin B12 is also available as tablets or lozenges placed under the tongue. These sublingual preparations arefrequently marketed as being superior to pills, although evidence suggests no difference in efficacy between oral andsublingual forms of vitamin B12. For those with poor B12 absorption and/or severe deficiency, vitamin B12 is available byprescription as an injection or as a nasal spray.
Interactions with Medications
Vitamin B12 has the potential to interact with certain medications. In addition, several types of medications mightadversely affect vitamin B12 levels. For example, proton pump inhibitors such as omeprazole (Prilosec®) andlansoprazole (Prevacid®), used to treat gastroesophageal reflux disease (GERD) and peptic ulcer disease, can interferewith vitamin B12 absorption from food by slowing the release of gastric acid into the stomach. Individuals taking these andother medications on a regular basis should discuss their vitamin B12 status with their healthcare providers.
For more information, visit these links:
NIH Office of Dietary Supplements Fact Sheet: Vitamin B12 - American Academy of Family Physicians -
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