(FORTUNE Magazine) – NEVER UNDERESTIMATE the power of a health fad. Calcium, that mundane mineral, is suddenly glamorous. Companies are touting decades-old products as rich in calcium and rolling out new ones to cash in on the craze, which began after the National Institutes of Health identified osteoporosis as a serious health problem in 1984. The bone-weakening disease accounts for about 1.3 million fractures a year, primarily in women past menopause. Calcium deficiency is one of the causes, so the NIH urged women to consume more calcium as a preventive measure. Calcium got still more attention last year when researchers reported that it may cut the risk of colon cancer and reduce high blood pressure. Among the new foods capitalizing on consumer concern are calcium-enriched milk, a pudding-coated granola bar called S'mores that Ralston Purina claims provides 25% of the U.S. recommended daily allowance of calcium per serving, and DairyCrisp, which calls itself ''the high calcium cereal'' and mentions osteoporosis on the package. Pet Inc., maker of DairyCrisp, says it is working on more calcium-rich food products and will introduce a drink with calcium this year. Dairy products are a standard source of calcium, and dairymen were quick to start milking that fact. Since September 1984 the National Dairy Board has spent more than $30 million on an advertising campaign pointing out the benefits of calcium. Consumption of dairy products had flagged because of worries about calories and cholesterol, but last year the quantity of milk products sold rose 3.3%. The board plans a new round of calcium-rich advertisements in the fall. Other familiar products with new messages about the calcium in them include Heinz's Alba cocoa mix, which changed its name last September to Alba High Calcium to attract older women. Heinz says that since then sales have run 50% ahead of projections. Coca-Cola hopes to revive its faltering Tab diet soft drink by adding calcium. In April, Coke started test-marketing Tab with 10% of the recommended daily allowance of calcium per 12-ounce serving. Nobody has taken better advantage of the calcium vogue than Tums antacid tablets, which are made of calcium carbonate. In October 1984, following the NIH warning about osteoporosis, Consumer Reports evaluated supplementary sources of calcium and rated Tums the cheapest. Norcliff Thayer, which makes Tums, debated whether to use calcium in its sales pitch. ''We were concerned that people who took Tums as an antacid would say we had changed the product, while people looking for calcium would say Tums is just an antacid,'' says Paul Fraioli, group marketing director. The company began running ads describing Tums as an antacid that is also rich in calcium. Tums's sales skyrocketed almost 50% last year to about $55 million. Sales of calcium supplement tablets rose by a similar percentage, to $131 million. Warner-Lambert, maker of rival Rolaids, introduced two calcium supplements last year and brought out a sodium-free version of Rolaids containing calcium carbonate. Rolaids ads mention calcium only as a side benefit. In January, Norcliff Thayer started promoting Tums as a calcium source first and only secondarily as an antacid. After 30 years as No. 2 to Rolaids, Tums tablets overtook Rolaids almost at once.