That's more than three tall cups at Starbucks, although drinking that much coffee or tea might bust suggested limits on caffeine.
The guidelines also allow men three times as much beer as sugary soda.
The report was paid for by the corporate parent of Lipton Tea, which is now using the scientists' advice to advertise tea's benefits.
The nutritionists say they didn't know the extent of Lipton's marketing campaign, and the company didn't play a role in the recommendations, which generally urge people to drink more water.
But beverage industry spokesmen and other nutritionists found fault with several of the guidelines. For example, whole milk is out, but moderate alcohol is OK.
In fact, the scientists say men can drink as much as 24 ounces of beer a day — more than the 16 ounces of low-fat milk or soy drinks they suggest, and three times their recommended limit for fruit juice.
The beverage industry also seized on the accompanying marketing campaign by Lipton, a part of Unilever Health Institute, which gave about $40,000 to finance the report. The company plans full-page ads in USA Today featuring the guidelines, along with a coupon for $2 off tea.
Among the scientists who wrote the guidelines is Dr. Walter Willett, chairman of nutrition at the Harvard School of Public Health and a widely quoted expert on numerous nutritional topics. He said he was unaware of the details of the marketing effort and wished it had not included such blatant promotion.
"This was sort of a new experience," he said of working with a private sponsor, whose $4,000 share of the fees he turned over to charity. Willett said the company had no role in what the scientists recommended.
"This was done with complete freedom to come to whatever conclusions we came to," he said.
The guidelines were published Wednesday in the American Journal of Clinical Nutrition. In general, they urge Americans to drink water and limit both sugar-sweetened and naturally sweetened drinks. Unsweetened tea and coffee are seen as acceptable substitutes for water.
Americans should limit beverages to 10 percent to 14 percent of their total calories — half what they comprise now, the group advised.
The panel of six scientists was assembled by Barry Popkin at the University of North Carolina in Chapel Hill, a longtime advocate of curbs on soda. He said he did so because federal dietary guidelines, including the food pyramid, focus on food and miss a significant contributor of calories.
One of every five calories in the average American's diet is liquid, something that doesn't produce the sense of fullness that food does. The portion of daily calories coming from sugar-sweetened drinks has roughly doubled over two decades, contributing to the nation's obesity problem, the report contends.
"We were quite dissatisfied" that federal guidelines and other advice focus on foods and general topics like dairy products, but don't spell out how much people should consume of each type of beverage, Popkin said.
In their guidelines, the nutritionists recommend 20 to 50 ounces of water a day. If other beverages are preferred, they recommend these daily limits for adults:
"Fruit smoothies are usually high-calorie versions of fruit drinks and, therefore, are not recommended," the report says. Likewise for whole milk, which contains high amounts of fat.
Besides Popkin and Willett, other members of the group were Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge, La.; Balz Frei, an Oregon State University biochemist; Dr. Benjamin Caballero, an obesity researcher at Johns Hopkins
Bloomberg School of Public Health; and Lawrence E. Armstrong, a physiologist at the University of Connecticut. Frei is a scientific adviser to Unilever.
The American Beverage Association says the report "has many factual shortcomings that are at odds with the USDA Dietary Guidelines — including the misguided suggestion that it's healthier to drink more alcohol than sweetened beverages and, in some scenarios, drink more tea than water.
"It also has a minuscule role for skim milk or low-fat milk in the diet," the association's statement says. "And there is no credible scientific rationale for limiting diet soft drinks to four servings per day."
Lisa Kadic, a dietitian and longtime consultant to the food and beverage industry, took issue with the report's contention that studies suggest some alcohol in moderation has health benefits.
"It did look like alcohol was being positioned as a better choice than (non-diet) soft drinks," she said.
While many studies have suggested some benefits from moderate alcohol consumption, such advice has long been contentious because of alcohol's risks.
An expert on nutrition and food policy who had no role in the report, New York University biologist Marion Nestle, said the panel's recommendations generally make good sense.
"If I were advising someone to lose weight, I'd start with soft drinks and juice drinks. Get rid of them," she said.
By Marilynn Marchione