When Helen Alexander shops for grocery bargains, she occasionally feels like she's being left in the cold -- and not just in the frozen-food section.

"Why do grocery chains advertise and sell food items cheaper for large orders and two-for-one prices?" asks the Arnold, Md., retiree. Doesn't that discriminate against seniors and singles?

"This is not fair for the elderly who do not need quantity because of storage problems or price," says Alexander. "Many are on limited budgets and cannot afford to buy volume, and many cannot use quantity."

For some shoppers, less is more. And they certainly don't want to pay more for less. But when supermarkets put products on sale, the idea usually is to move inventory.

"While we all love a bargain, we have to remember that the reason that manufacturers offer these deals to supermarkets is that they want -- or sometimes need -- to sell more product quickly," says Phil Lempert, a California-based food industry analyst known as the "supermarket guru" and author of "Being the Shopper: Understanding the Buyer's Choice" (John Wiley & Sons; 2002). "It could be the end of a quarter, or sales in a particular store or geographic area are down, and they need to induce more shoppers to try their products."

Lempert says stores don't always dictate the terms of their sales prices. "Most supermarkets will honor a 'two-fer' cost reduction on just one item when they can," he says. "But sometimes the manufacturer won't allow it, and with today's highly detailed register receipts and reporting, it's easy to know when a retailer breaks the rules. And when they do, the manufacturer can pull the product discount for everyone."

Michael Sansolo, senior vice president of the Food Marketing Institute, a trade group headquartered in the District, says consumers frequently ask similar questions about coupons. " 'Do I have to buy four products to get one free?' That's the rule sent down by the manufacturers."

Sansolo's advice is, if you don't like a supermarket policy, speak up. "If these things happen all the time in your store, mention it to the store manager," he says. "Make them sensitive to your needs."

A survey of some supermarkets in the Washington area finds that stores sort out their discounts differently for the single-item customer:

* Giant Foods: "For the two-for-one price, you do need to buy two to get the sale price," says spokesman Jamie Miller.

* Harris Teeter: "If it's a 'BOGO' [buy one, get one], you must buy both," says spokeswoman Jennifer Panetta. "If it's a multiple item, the customer only has to buy one and he receives the sale price."

* Food Lion: "On our buy-one-get-another offers, you can get a single item for half price," says spokesman Jeff Lowrance.

* Safeway: "Our Safeway Club discounts include buy-one-get-one-free offers, and we have some things that are two for $5 or three for $4.98," says spokesman Craig Muckle. "If you buy the incomplete grouping of the item, you would still get it for the sale price."

* Shoppers Food Warehouse: "If it were five-for-a-dollar, yes, one would be 20 cents," says spokeswoman Rhonda Furmanski. "As far as buy-one-get-one-free, we would not sell one for half price."

* Wegman's: The chain promotes "consistent everyday low prices" so customers don't have to "run around town chasing deals," says spokeswoman Jo Natale, adding that for multiple-item promotions, "in almost every case you can buy one at the sale price."

In stores where buying the whole deal is required, Lempert suggests shoppers take the items to the courtesy counter and ask if the store will give the discount on one. "If not, and it's a product that will not spoil, see if it is one that you may use over the next 30 or 60 days," he says. "It may well be worth the savings to buy both."

Sansolo reminds customers such as Alexander that they have the trump card in the highly competitive grocery game: "There's always another supermarket to shop at."

Got questions? A consumer complaint? A helpful tip? E-mail details to oldenburgd@washpost.com or write Don Oldenburg, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.