SITTING under an umbrella at the beach is no substitute for using sunscreen, a new study shows.

About 78 percent of people who used only an umbrella to protect themselves from the sun during a few hours at the beach were sunburned the next day, compared to only 25 percent of people who used sunscreen with a sun protection factor (SPF) of 100, researchers found.

But while sunscreen prevented more sunburns than a large umbrella, neither method was 100 percent effective.

"It’s good to have a holistic approach," said lead author Dr. Hao Ou-Yang. "You need to think of a combination of measures."

Ou-Yang and a coauthor both work for Johnson and Johnson Consumer Inc. in Skillman, New Jersey. The company partly funded the study and is the parent company of Neutrogena Corp, which manufactures the sunscreen used in the research.

Ou-Yang told Reuters Health that people should use a combination of approaches like using a high-SPF sunscreen, wearing clothes and a hat and seeking shade.

For the new study, the researchers recruited 81 fair-skinned people to sit in the midday sun at Lake Lewisville, Texas, for 3.5 hours in August 2014. The participants were randomly assigned to use SPF 100 sunscreen or to use a standard-size beach umbrella.

The participants were checked the next day for sunburns.

The researchers found 142 sunburned areas on the 41 people who used an umbrella, but only 17 on those who used sunscreen.

Overall, 32 of those who used umbrellas ended up with sunburns, compared to 10 in the sunscreen group.

The researchers explain in JAMA Dermatology that beach umbrellas are designed to block direct rays from the sun but they don't protect against scattered rays.

"You don’t want to just trust one method for sun protection," said Dr. Jennifer Stein, a dermatologist at NYU Langone Medical Center in New York City. "The safest way to be outside is avoid the middle of the day, sit in the shade, wear protective clothing and sunscreen."

People should use a sunscreen with an SPF of at least 30, said Stein, who was not involved with the new study. She said one reason to buy a sunscreen with a higher SPF is that consumers typically don't apply as much of it as companies do when they test the product.

Using a combination of protective factors can prevent sunburns even among people with the fairest skin, she said.

"There is no reason to be a vampire," said Stein. "Go on vacation. Go to the beach and have an active lifestyle. Just be careful."