Vitamins B-12 and B-1, or thiamine, are two of the eight types of B vitamins your body uses daily to metabolize nutrients from food into usable energy. The B vitamins work together to perform a variety of bodily functions including the formation of red blood cells and nurturing your cognitive functions. Neither vitamin B-12 nor thiamine has an upper limit dose, but you should not exceed the standard recommended intake without consulting a physician.
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Vitamin B-12 Daily Intake
Vitamin B-12 is unique because, unlike the other water-soluble B vitamins, your body stores several years worth of B-12 in your liver. This makes vitamin B-12 deficiency rare unless you have a gastrointestinal disorder that impairs nutrient absorption, or if you are a strict vegetarian not getting adequate B-12 supplementation. The daily recommended intake of vitamin B-12 for men and women is 2.4 micrograms. According to the Office of Dietary Supplements no upper tolerable limit -- the highest level you can take without risk of adverse side effects -- for vitamin B-12 exists because of the low potential for toxicity.
Thiamine Daily Intake
Thiamine is a water-soluble vitamin that your body does not store; you must replace it daily from dietary sources. Without adequate intake, depletion or deficiency symptoms from thiamine can appear within 14 days. The daily recommendation is 1.2 milligrams for adult males and 1.1 milligrams for adult females. The Linus Pauling Institute notes a small number of anaphylactic reactions occurred from large intravenous doses of thiamine. However, no tolerable upper level intake is established because research does not indicate toxic effects from excess dietary or supplement consumption of thiamine.
Get your daily intake of vitamins B-12 and thiamine from food sources rather than supplements unless otherwise directed by your physician. Animal-based foods are rich in vitamin B-12 including salmon, trout and tuna with 1.0 to 5.4 micrograms per 3-ounce serving. Milk, cheese and yogurt have 0.9 to 1.4 micrograms per 1-cup serving. If you prefer non-animal based foods, fortified whole grain cereals contain 1.5 to 6.0 micrograms per serving. Thiamine rich beans and nuts yield .17 to .19 milligrams per 1/2 cup serving, while brown rice, wheat bread and wheat germ cereals contain .10 to 4.47 milligrams. Animal based sources of thiamine include milk, eggs and pork with .03 to .72 milligrams per serving size.
Vitamins and Interactions
Although vitamin B-12 and thiamine do not have a tolerable upper limit, taking supplemental forms of these vitamins may cause interactions with medications. Vitamin B-12 has the potential to interact with antibiotics, diabetes medications and proton pump inhibitors to treat reflux disease or peptic ulcers. Thiamine may interact with anticonvulsant medications to treat seizure disorders, diuretics and some cancer medications. Consult your physician before taking vitamin supplements to determine safety for your condition and potential side effects. Itching, diarrhea, drowsiness and muscle weakness may occur when first taking vitamin B-12 or thiamine supplements.