BOSTON -- They can help you lose weight fast, but low-carbohydrate diets have at least one pitfall: Cutting all those carbs also cuts needed nutrients.

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With 40 million Americans skimping on carbs, it was only a matter of time before specialized vitamins hit the shelves. But do they work?

Geoffrey Ginn needs a pill organizer for all the supplements he's taking, such as extra B-vitamins and other nutrients often depleted by the Atkins diet. He's lost 40 pounds on the plan but doesn't want his health to suffer.

"When you're depleting your system of carbs and sugar, you're initially going to have lower energy," said Ginn.

Depleting B-vitamins found in foods not allowed in a low-carb diet, such as bread and pasta, can hurt your nervous system and have an effect on osteoporosis, reported WCVB-TV in Boston.

Supplement makers have come up with a solution: a new type of vitamin developed for the low-carb lifestyle.

But they can cost up to three times as much as regular multivitamins. Bayer, the maker of Carb Smart, said the added cost is worth it. The supplement contains specialized ingredients such as higher B-vitamins, antioxidants, potassium, and biotin, which Bayer claims can turn fats and proteins into energy.

But nutrition experts question whether there's an added value.

"It makes expensive urine but does not give you more balance, more nutrition or more health," said Dr. George Blackburn, of Beth Israel Deaconess Medical Center in Boston.

"A multivitamin is still going to have everything you need in it. America is just being marketed," said Dr. Mark Mincolla, a nutritional therapist based in Massachusetts.

Blackburn and Mincolla said the solution is simple: Don't eliminate all carbs and add a few good ones.

"I advise people eat small amounts of right kinds of fruits. I say they should get a quarter cup of nuts and seeds a day to get your vitamin E and B complexes. I think you can do it dietarily," said Mincolla.

For Ginn, adding specialized vitamins has made a difference.

"I think my ability to handle stressful situations has increased. I'm a little more calm," he said.

Experts say the new vitamins won't hurt you, but you're wasting your money. They recommended a regular multivitamin for about 7 cents a day.