The product: Judging from the slew of energy products taking up space in supermarkets and convenience stores, B vitamins have become the new go-to ingredients for a quick pick-me-up.

A 2-ounce gulp of the popular liquid supplement 5-Hour Energy contains an astounding 8,333% of the recommended dietary allowance of vitamin B-12 and 2,000% of the RDA for vitamin B-6. (You'll get a mere 100% of the RDA for folic acid, also known as vitamin B-9.) A 12-ounce Red Bull, the near-official energy drink of the high school and college set, offers 360% of the RDA for vitamin B-6, 120% of B12, 140% of niacin (vitamin B3) and more sugar than you'd get in a can of Coke. B vitamins have also made their way into other energy drinks such as Cranergy, a cranberry and green tea extract drink from Ocean Spray.

These examples all contain caffeine for an extra boost; 5-Hour Energy does sell a caffeine-free version, and there's a sugar-free version of Red Bull. None of these "light" varieties skimp on the vitamins.

 

You can expect to pay about $5 for two 2-ounce bottles of 5-Hour Energy. Users are instructed to down an entire bottle for "maximum energy." (If you're willing to make do with 4,000% of your daily quota for B-12, you could just drink half and save the rest for later.) A 12-ounce can of Red Bull costs about $3. A 46-ounce bottle of Cranergy costs about $4.

The claims: A TV spot for 5-Hour Energy featuring burned-out office workers says that the product contains a "powerful blend of B vitamins for energy" that will let you "sail through your day without feeling jittery or tense." The 5-Hour Energy website clarifies that the supplement is supposed to "provide mental alertness, focus and improved mood rather than physical energy." The website for Red Bull says that B vitamins "play an important role in energy metabolism" and "are shown to support mental and physical performance."

The bottom line: The Healthy Skeptic isn't part of the Red Bull generation, but he did down 2 ounces of 5-Hour Energy right before his traditional afternoon slump. It turns out that a megadose of vitamin B-12 can go down pretty smoothly, if you don't mind the taste of Fresca gone flat. The caffeine -- about as much as in a cup of coffee -- seemed to kick in right away. But if the B vitamins added anything to the caffeine buzz, the effects were too subtle to notice. Energy, mood, thinking skills -- all were unfortunately ordinary and familiar.

Contrary to what ads would have us believe, B vitamins aren't little packets of energy, says Hope Barkoukis, an associate professor of nutrition at Case Western Reserve University in Cleveland and chairwoman of Sports, Cardiovascular and Wellness Nutritionists, a practice group of the American Dietetic Assn. "It's brilliant marketing," she says, "but it doesn't have any basis."

It's true that the vitamins help unlock the energy in foods, Barkoukis says, but weary office workers can't expect to get a jolt from extra B vitamins in any form. The reason, she says, is simple: Just about everyone in America already gets all of the B vitamins they could possibly need in their diets.

For example, a person could get the full recommended dietary allowance of B-6 (1.3 milligrams) with a single bowl of fortified cereal or a chicken breast with a baked potato. Likewise, just 3 ounces of beef or a couple of dairy products each day provide the RDA for B-12 (2.4 micrograms).

Extra B vitamins are generally just flushed out of the system, Barkoukis says. The body can easily handle huge doses of vitamin B-12, but the Institute of Medicine warns that more than 100 milligrams of B-6 each day -- what you'd get from 2 1/2 bottles of 5-Hour Energy -- may damage nerves in the arms and legs.

Some people, especially the elderly, do need extra B vitamins as they have trouble absorbing the nutrients, says Victoria Drake, a researcher with the Linus Pauling Institute at Oregon State University in Corvallis. In such cases, doctors may recommend vitamin B supplements, even shots. But for typical consumers of energy supplements or drinks, B vitamins are nothing more than a "gimmick," she says.

In other words, the 5-Hour Energy ad might have been more plausible if it were set in a nursing home instead of an office.