Citrus is famous for vitamin C, but other fruits deliver even more of the nutrient important during cold and flu season. These fruits contain the most vitamin C.

Fruits high in vitamin C get a lot of attention during cold and flu season, and for good reason.

Vitamin C plays a role in keeping the immune system strong, which helps people get better when they get ill, says Natalie Rizzo, nutrition editor for TODAY.

"Since colds and flus are rampant this time of the year, it's important to have enough vitamin C in your diet to make sure you are able to recover quickly when you do get sick," Rizzo says.

"It's very easy to get enough vitamin C through your diet alone. The body is able to absorb nutrients from food better than supplements, so I always recommend starting with foods."

Vitamins can fill the gaps if you don't eat enough plant-based foods with vitamin C, but "mega-doses" of the nutrient won't prevent most people from getting sick, she notes.

Still, people who already have a vitamin C deficiency may lower their risk of getting a cold by getting plenty of the nutrient, registered dietitian Carol Johnston, Ph.D., who is an expert on vitamin C metabolism, previously told TODAY.com.

The powerful antioxidant also protects cells from damage and is important for healthy skin, bones, teeth and gums.

The recommended daily intake of vitamin C is 90 milligrams for men and 75 milligrams for women, according to the National Institutes of Health. Children need less.

The safe upper limit is 2,000 milligrams a day, though the nutrient doesn't cause serious problems even at high doses, the NIH notes. The body flushes out excess vitamin C in urine.

Citrus is famous for vitamin C, but other fruits deliver even more of the nutrient. Here are nine fruits highest in vitamin C:

Surprise! You may think of them as vegetables, but bell peppers are officially classified as fruits and they are vitamin C superstars, especially the yellow kind.

Red bell peppers are one of Rizzo's favorite snacks to boost the immune system during cold and flu season.

They're naturally low in calories and fat and provide fiber. In addition to vitamin C, they contain vitamin A, B vitamins, minerals and antioxidants.

Colorful, sweet and crunchy, they can be sliced and then dipped in hummus or tzatziki for a filling snack, Rizzo says.

The sweet tropical fruit contains almost double the amount of vitamin C found in an orange, plus guava is very high in antioxidants, potassium and fiber. That translates into benefits for gut and heart health.

Guava is also one of the fruits with the most protein.

You can add it to smoothies, salads and savory dishes.

"Strawberries are an excellent source of vitamin C, which plays a role in immune function and fighting free radicals associated with cancer and heart disease," registered dietitian Jackie Newgent previously told TODAY.com.

"Strawberries are loaded with flavonoids and other health-protective plant nutrients, so think of them as a super fruit."

They're also one of the fruits with the least sugar.

Papaya is one of the "longevity superfoods" eaten in the Blue Zones -- places around the world where people live extraordinarily long and healthy lives.

Besides vitamin C, it's packed with nutrients including magnesium, potassium, folate, lycopene, and vitamins A, C, E and K. It also contains a bit of iron and calcium.

Dietitians are impressed by pineapple's high vitamin C content, especially since it helps the body absorb plant sources of iron.

"So as people are transitioning to more of a plant-based way of eating, sometimes having extra vitamin C can help your body absorb iron from foods like spinach or beans to make sure you're not deficient in iron," Sarah Rivenburgh, a registered dietitian at OhioHealth, previously told TODAY.com.

Pineapple also contains insoluble fiber, or roughage, which helps to keep the bowels moving regularly; and bromelain, an enzyme that breaks down proteins and has anti-inflammatory properties.

Oranges, grapefruits and tangerines are a go-to source of vitamin C for many people. They're in season in winter and spring, making them peak choices during cold and flu months. Tangerines are an especially portable, tasty, juicy, easy-to-peel snack.

It's best to eat the whole fruit to get vitamin C rather than drinking the juice, Rizzo advises. You'll get the fiber for satiety and gut health, including pectin, a type of fiber found in the membranes and pith of citrus fruits that can help lower cholesterol.

Sweet-tart with a distinct bright green color, kiwis are "exceptionally high in vitamin C" and contain good amounts of fiber, potassium, vitamin E, folate and antioxidants, studies have found.

Actinidin, a natural enzyme unique to kiwifruit breaks down protein, which helps with digestion, researchers note.

Eating kiwis may even improve sleep because they contain serotonin, a neurotransmitter that's involved in sleep-wake cycles, one study found.

Tasty, rich in vitamin C and full of soluble fiber -- the type that turns into a gel in the digestive tract -- mango is also one of the fruits highest in sugar for healthy energy.

Registered dietitian Samantha Cassetty includes mangoes on her list of the 15 healthiest fruits because of their carotenoid compounds, which give mangoes their golden color and provide health benefits.

Cantaloupe is a hydrating, low-calorie fruit that's high in both vitamin C and A.

It's also low in sugar and high in protein for a fruit. Registered dietitian Samantha Cassetty suggests serving it with Greek yogurt, honey and pistachios for a delicious Mediterranean diet-style dessert or breakfast.

It also pairs well with prosciutto for a more savory snack.