Vitamin B12

Nutrient Library: Vitamin B12

Vitamin B12:

  • What does it do?
  • How much do you need?
  • What are the best food sources?
  • What happens if you don't get enough?
  • What happens if you get too much?

What does it do?
Vitamin B12 is a water-soluble B vitamin that helps transform fats and proteins from foods into energy and works with folic acid to produce normal red blood cells. An adequate supply of vitamin B12 is also necessary for normal neurological function.

How much do you need?
The following table lists the recommended intake for healthy people based on current scientific information.

Life Stage Group Recommended Dietary Allowance/Adequate Intake Tolerable Upper Intake Level (UL)
Infants (micrograms/day) (micrograms/day)
0-6 mo.
7-12 mo.
Not determinable due to lack of data on adverse effects and concern about inability to handle excess amounts. Source should be from food only to prevent high levels of intake.
1-3 y
4-8 y
9-13 y
14-18 y
19-30 y
31-50 y
51-70 y
> 70 y
9-13 y
14-18 y
19-30 y
31-50 y
51-70 y
> 70 y
< 18 y
19-30 y
31-50 y
< 18 y
19-30 y
31-50 y

NOTE: The table is adapted from the Dietary Reference Intakes reports. Recommended Dietary Allowances (RDAs), when available, are in bold type; Adequate Intakes (AIs) are followed by an asterisk(*). RDAs and AIs may both be used as goals for individual intake. RDAs are set to meet the needs of almost all individuals (97 to 98 percent) in a group. For healthy breastfed infants, the AI is the mean intake. The AI for other life stage and gender groups is believed to cover the needs of all individuals in the group, but lack of data means the percentage of individuals covered by this intake cannot be specified with confidence.

UL = The maximum level of daily nutrient intake that is likely to pose no risk of adverse effects. Unless otherwise specified, the UL represents total intake from food, water and supplements.

What are the best food sources?
Vitamin B12 is found naturally in animal-based foods, such as meat, fish, poultry, eggs and dairy foods. Particularly rich sources of vitamin B12 include shellfish, herring, sardines, trout and some game meats. Vegans and strict vegetarians can get B12 from some fortified foods, such as ready-to-eat cereals and meal replacements (e.g., bars and drinks).

What happens if you don't get enough?
Nutritional deficiency of this vitamin is rare among those under 50 years old because the human body can store several years' worth. However, when it does occur it causes pernicious anemia (also known as megaloblastic anemia), a condition in which the body fails to absorb B12 and becomes unableto produce enough healthy red blood cells. Symptoms include low counts of abnormally large red blood cells, fatigue, nerve damage, numbness and tingling of the extremities (e.g. fingers, toes), cognitive changes, a sore tongue or loss of appetite.

Adults over 50 years old are often at risk of not getting enough vitamin B12. This may be because of a decrease in the production of stomach acid with age (which is needed to extract B12 from food) or malabsorption problems due to the presence of atrophic gastritis (a chronic inflammation that causes damage to the lining of the stomach and results in the body's inability to extract vitamin B12 from dietary proteins). Thus, adults over 50 years old are advised to consume foods fortified with vitamin B12 or a supplement containing B12, both of which are more available sources to this population. Consult with your physician if you are worried that this might be you.

Individuals who follow a vegan or strict vegetarian diet (B12 is found in food from animals) and anyone with a digestive problem that impairs absorption of nutrients (e.g., celiac disease, Crohn's) are also at a higher risk of vitamin B12 deficiency. Consult your physician if you fall into one of these categories.

What happens if you get too much?
It's not likely that you will experience harmful effects from consuming too much vitamin B12, because your body can only absorb a small amount of the B12 you receive from foods and supplements. However, moderation is still the best approach, as studies have not specifically looked at the harmful effects of excess vitamin B12.


Lemon-Garlic Shrimp & Vegetables
Here's a healthy twist on shrimp scampi. We left out the butter and loaded the dish up with red peppers and asparagus for a refreshing spring meal. Serve with quinoa, whole-wheat couscous or linguine.

Makes 4 servings

ACTIVE TIME: 35 minutes
TOTAL TIME: 35 minutes

  • 4 teaspoons extra-virgin olive oil, divided
  • 2 large red bell peppers, diced
  • 2 pounds asparagus, trimmed and cut into 1-inch lengths
  • 2 teaspoons freshly grated lemon zest
  • 1/2 teaspoon salt, divided
  • 5 cloves garlic, minced
  • 1 pound raw shrimp (26-30 per pound), peeled and deveined
  • 1 cup reduced-sodium chicken broth
  • 1 teaspoon cornstarch
  • 2 tablespoons lemon juice
  • 2 tablespoons chopped fresh parsley

Heat 2 teaspoons oil in a large nonstick skillet over medium-high heat. Add bell peppers, asparagus, lemon zest and 1/4 teaspoon salt and cook, stirring occasionally, until just beginning to soften, about 6 minutes. Transfer the vegetables to a bowl; cover to keep warm.

Add the remaining 2 teaspoons oil and garlic to the pan and cook, stirring, until fragrant, about 30 seconds. Add shrimp and cook, stirring, for 1 minute. Whisk broth and cornstarch in a small bowl until smooth and add to the pan along with the remaining 1/4 teaspoon salt. Cook, stirring, until the sauce has thickened slightly and the shrimp are pink and just cooked through, about 2 minutes more. Remove from the heat. Stir in lemon juice and parsley. Serve the shrimp and sauce over the vegetables.

NUTRITION INFORMATION: Per serving: 226 calories; 7 g fat (1 g sat, 4 g mono); 174 mg cholesterol; 14 g carbohydrate; 28 g protein; 4 g fiber; 514 mg sodium; 670 mg potassium. Nutrition bonus: Vitamin C (210% daily value), Vitamin A (80% dv), Folate (53% dv), Iron (25% dv). 1 Carbohydrate Serving. Exchanges: 2 vegetable, 3 lean meat, 1 fat.

More Healthy Shrimp Recipes and Tips

Roasted Ratatouille with Eggs & Cheese
Served with plenty of crusty bread and a green salad, this is a perfect dish for brunch or a light supper. Roasting is an excellent technique for ratatouille because the vegetables retain a distinct texture, yet the flavors meld. Pay close attention while you are cooking the eggs in the oven; they turn from nicely set to hard as a rock in a flash.

Makes 4 servings

ACTIVE TIME: 25 minutes
TOTAL TIME: 1 hour 40 minutes

  • 1 small eggplant (about 12 ounces), trimmed, peeled and cut into 1/2-inch pieces
  • 1 medium onion, cut into 1/2-inch pieces
  • 1 small zucchini, cut into 1/2-inch pieces
  • 1 small red bell pepper, seeded and cut into 1/2-inch pieces
  • 2 cloves garlic, minced
  • 2 tablespoons plus 2 teaspoons extra-virgin olive oil
  • 1/4 teaspoon salt
  • Freshly ground pepper to taste
  • 1 28-ounce can plum tomatoes with juices
  • 2 tablespoons torn fresh basil leaves, plus more for garnish
  • 1 tablespoon finely chopped fresh parsley
  • 4 large eggs
  • 4 ounces part-skim mozzarella, thinly sliced and cut into 1/4-inch strips
  • 4 1/2-inch-thick slices Italian bread, preferably whole-wheat
  1. Preheat oven to 400°F. Lightly coat a large rimmed baking sheet with cooking spray.
  2. Combine eggplant, onion, zucchini, bell pepper and garlic in a large bowl; drizzle with 2 tablespoons oil; toss to coat. Spread the vegetables on the prepared baking sheet. Season with salt and pepper.
  3. Roast the vegetables, uncovered, turning often, until lightly browned and tender, about 45 minutes. Transfer the vegetables to a 9-by-13-inch baking dish. Cut tomatoes into chunks. Stir the tomatoes (and their juices), basil and parsley into the vegetables. Cover with foil.
  4. Bake until the ratatouille is hot and bubbling, about 20 minutes. Remove from the oven.
  5. With a large spoon, make four evenly spaced indentations in the hot ratatouille. Carefully break an egg into each indentation. Sprinkle cheese over the vegetables and eggs. Bake, uncovered, until the eggs are set and the cheese is melted, 8 to 10 minutes.
  6. While the eggs are baking, toast bread and drizzle each slice with 1/2 teaspoon olive oil. Divide bread slices among 4 plates or shallow soup bowls.
  7. To serve, lift an egg and ratatouille from the baking dish and place on top of a slice of toasted bread. Spoon the remaining vegetables and juices around the edges, distributing evenly. Garnish with more basil, if desired.

NUTRITION INFORMATION: Per serving: 402 calories; 21 g total fat (6 g sat, 11 g mono); 227 mg cholesterol; 34 g carbohydrate; 22 g protein; 7 g fiber; 775 mg sodium; 419 mg potassium. 2 Carbohydrate Servings.

MAKE AHEAD TIP: Prepare through Step 4, cover and refrigerate for up to 2 days. Reheat before continuing.

More Healthy Brunch Recipes

Manhattan Crab Chowder
If you like Manhattan clam chowder, you'll love how delicious our version is when made with crab. Take your time to finely dice the vegetables and the soup will cook faster. Make it a meal: All you need is crusty bread or oyster crackers and a tossed salad and you've got dinner.

Makes 6 servings, about 1 1/2 cups each

ACTIVE TIME: 30 minutes
TOTAL TIME: 40 minutes

  • 2 tablespoons extra-virgin olive oil
  • 1 cup finely diced onion
  • 1 cup finely diced cored fennel bulb, plus 2 tablespoons chopped fronds, divided
  • 2 tablespoons minced garlic
  • 2 teaspoons Italian seasoning blend
  • 1/8 teaspoon salt
  • 1/2 teaspoon freshly ground pepper
  • 1 14-ounce can reduced-sodium chicken broth or vegetable broth
  • 1 1/2 cups water
  • 2 cups precooked diced potatoes (see Tip)
  • 2 cups canned crushed tomatoes
  • 1 pound pasteurized crabmeat, drained if necessary

Heat oil in a large saucepan over medium heat. Add onion, fennel bulb, garlic, Italian seasoning, salt and pepper and cook, stirring often, until the vegetables are just starting to brown, 6 to 8 minutes.

Add broth, water and potatoes; bring to a boil. Reduce heat to a simmer and cook until the vegetables are tender, 3 to 5 minutes. Stir in tomatoes, crab and fennel fronds. Return to a boil, stirring often; immediately remove from heat.

NUTRITION INFORMATION: Per serving: 211 calories; 5 g fat (1 g sat, 4 g mono); 88 mg cholesterol; 21 g carbohydrate; 19 g protein; 3 g fiber; 647 mg sodium; 513 mg potassium. Nutrition bonus: Iron (35% daily value), Vitamin C (30% dv), Calcium (15% dv). 1 1/2 Carbohydrate Servings. Exchanges: 1 starch, 1 vegetable, 2 very lean meat, 1 fat

Tips: Look for precooked diced potatoes in the refrigerated section of most supermarket produce departments-near other fresh, prepared vegetables.

We call for convenient canned crushed tomatoes, but you only need 2 cups; store leftover tomatoes in an airtight container for 1 week in the refrigerator or months in the freezer.

More Healthy Seafood Recipes and Cooking Tips

From with permission. © 2008 Eating Well Inc.

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