Big guns heed call of consumers.(CONSUMABLES: A perusal of ad inserts proves the importance that drug chains give the category.)(colas for consumers in need of healthy beverages)

NEW YORK -- Coca-Cola Co. and Pepsi-Cola North America are debuting new diet colas in an appeal to consumers looking for more healthful beverage choices.

"The biggest trend impacting sales in the beverage industry is health and wellness," says Gary Hemphill, managing director at Beverage Marketing, a consulting firm. "The industry has reached an area of specialization; we'll likely see a growing assortment of brands and choice--more niche brands and fewer megabrands."

Both major soft drink manufacturers have increasingly turned to such noncarbonated drinks as bottled water, tea and juice in response to falling sales of carbonated soft drinks. According to Beverage Digest, soft drink volume …