A panel of scientists issued new nutritional guidelines for children on Wednesday, describing in detail what they should be allowed to drink in the first years of life. The recommendations, among the most comprehensive and restrictive to date, may startle some parents.

Babies should receive only breast milk or formula, the panel said. Water may be added to the diet at 6 months; infants receiving formula may be switched to cow’s milk at 12 months. For the first five years, children should drink mostly milk and water, according to the guidelines.

Children aged 5 and under should not be given any drink with sugar or other sweeteners, including low-calorie or artificially sweetened beverages, chocolate milk or other flavored milk, caffeinated drinks and toddler formulas.

Plant-based beverages, like almond, rice or oat milk, also should be avoided. (Soy milk is the preferred alternative for parents who want an alternative to cow’s milk.)

In what may come as a shock to parents with pantries full of juice boxes, the panel also said that young children should drink less than a cup of 100% juice per day — and that none at all is a better choice.

The new guidelines were produced by Healthy Eating Research, a nutrition advocacy group, and funded by the Robert Wood Johnson Foundation. The recommendations are likely to be influential, as they have been endorsed by the American Academy of Pediatrics, the Academy of Nutrition and Dietetics, the American Heart Association and the American Academy of Pediatric Dentistry.

The cautions against sweetened beverages arrive amid persistent concerns about childhood obesity, which can set the stage for lifelong chronic illness. About 19% of children in the United States are obese.

“Close to half of all 2- to 5-year-olds in the U.S. drink sugary drinks every day, which we know increases their risk of obesity, diabetes and other health problems,” said Megan Lott, deputy director of Healthy Eating Research.

“These recommendations simplify everything for parents — water, milk and limited amounts of 100% fruit juice,” she added.

Children do not need juice and are better off eating fruit, the panel said. Excessive juice consumption can lead to dental decay and weight gain, and is linked to overall poor nutrition.

“When we talk about empty calories that are consumed through beverages and the number of calories people get from sugar-sweetened drinks, we’re not just talking about soda,” said Dr. Richard Besser, president and chief executive of the Robert Wood Johnson Foundation. “Juice is another source of calories that nutritionally aren’t terrific.”

Recommendations to limit juice are not new: The pediatrics academy has long advised that babies not be given juice till they are a year old, and that the amount of juice be limited to 4 ounces per day for children between ages 1 and 3.

Plant-based milk beverages like almond, oat and rice milk often contain added sweeteners or artificial flavorings, and are less nutritious than cow’s milk, a glass of which contains 8 grams of protein along with nutrients such as calcium.

With the exception of soy milk, plant-based milks are poor in protein. Though they are often fortified, scientists do not know whether people are able to absorb these nutrients as efficiently as those naturally present in other foods.

Formulas marketed for toddlers are usually unnecessary, since most toddlers eat solid food; the products tend to be expensive and often contain added sugars, Lott said.

There is no rigorous data from studies of children about the safety of artificially sweetened drinks and other low-calorie sweetened beverages, she said, and the products can condition a child to prefer sweet drinks generally.

A spokesman for the American Beverage Association, William Dermody, said beverage companies agree that “it’s important for families to moderate sugar consumption to ensure a balanced, healthy lifestyle, and this is especially true for young children.”

A spokesman for the Juice Products Association, however, said that for children with limited access to fresh produce, juice can help improve fruit intake. Federal dietary guidelines recognize three-quarters of a cup of 100% juice as equivalent to three-quarters of a cup of fruit.

But many products that appear to contain natural juice may actually contain only a small amount of real juice, experts cautioned, saying parents must read labels carefully.

Children develop preferences for foods and beverages at a young age, and the recommendations are made with an eye to shaping a healthy palate.

About a third of children and adolescents in the United States are overweight or obese, conditions that increase the risk of developing chronic illnesses, such as high blood pressure, high cholesterol, sleep apnea, Type 2 diabetes, heart disease, stroke and some cancers.

“The hope is that through this approach, you’ll help your child develop a taste for what’s good for them,” Besser said. Though the occasional glass of 100% juice is not going to be harmful, “what you want your children as they grow older to be drinking primarily is water.”

The new recommendations are broken down by age group:

Birth to six months: Infants should drink only breast milk or infant formula. They should not drink juice, milk, flavored milk, so-called transition or weaning formulas (also called toddler milks, growing-up milks or follow-up formula), low-calorie sweetened beverages (diet or “light” drinks, or those sweetened with Stevia or Sucralose).

These children also should not receive plant-based and nondairy “milks,” caffeinated beverages (soda, coffee, tea, energy drinks) or sugar-sweetened beverages (soda, fruit drinks and fruit-flavored drinks, sports drinks, energy drinks, sweetened water, and sweetened coffee or tea).

6 to 12 months: Babies should still rely on breast milk or infant formula. Once they have begun eating solid food, they can start sipping water. Parents should avoid juice, milk, flavored milk, transition formulas, low-calorie sweetened beverages, plant-based and nondairy milks, caffeinated beverages, and sugar-sweetened beverages.

12 to 24 months: Children should drink one to four cups of water daily, and they can start drinking plain pasteurized whole milk. They should have no more than 4 ounces of 100% fruit juice per day; the juice may be watered down. Parents should avoid other drinks (flavored milk, transition formulas, caffeinated drinks, plant-based and nondairy milks, sugar-sweetened beverages and low-calorie sweetened beverages).

2 to 3 years old: Toddlers should drink one to four cups of water daily and transition to fat-free or low-fat (1% fat) milk. They should drink no more than 4 ounces of 100% juice and should not be given other drinks.

4 to 5 years old: These toddlers should drink 1.5 to five cups of water a day, skim or low-fat milk, and no more than 4 to 6 ounces of 100% fruit juice. They should not be given other drinks.

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