Summary Blueberries are rich in essential nutrients and antioxidants, which play a role in preventing cell damage and may reduce chronic disease risk. Blackberries are sweet and nutritious dark-blue berries that offer several health benefits. A single cup (144 grams) of blackberries packs nearly 8 grams of fiber, 40% of the recommended Daily Value (DV) for manganese, and 34% of the DV for vitamin C ( 11 ). The same serving also provides 24% of the DV for vitamin K, making blackberries one of the richest fruit sources of this essential nutrient ( 11 ). Vitamin K is necessary for blood clotting and plays an important role in bone health ( 12 ).
Though the relationship between vitamin K and bone health is still being researched, scientists believe that a lack of vitamin K may contribute to osteoporosis, a condition in which your bones become weak and fragile ( 13 ). While leafy green vegetables are highest in vitamin K, a select few fruits, such as blackberries, blueberries, and prunes, also contain ample amounts to help you meet your daily needs ( 3 , 11 , 14 , 15 ). Summary Blackberries are loaded with fiber, manganese, and vitamin C. They’re also one of the few fruits that are high in vitamin K, which plays an essential role in blood clotting and bone health. Elderberry is one of the most popular plant remedies worldwide ( 16 , 17 ). This blue-purple fruit may help defend against the cold and flu by boosting your immune system. It’s also been shown to help people recover from these illnesses faster ( 18 ).
Research suggests that the beneficial plant compounds in elderberries may activate healthy immune cells that help fight off cold and flu viruses ( 19 ). What’s more, test-tube studies indicate that concentrated elderberry extracts may fight the flu virus and prevent it from infecting cells, though this is still under investigation (20, 21 ). In one 5-day study, taking 4 tablespoons (60 ml) of a concentrated elderberry syrup daily helped people with the flu recover an average of 4 days quicker than those who did not take the supplement ( 22 ). These berries are also high in vitamins C and B6, two nutrients known to promote a healthy immune system. Just 1 cup (145 grams) of elderberries provides 58% and 20% of the DVs for vitamins C and B6, respectively ( 23 , 24 , 25 ). Keep in mind that it may be best to eat these berries cooked. Raw elderberries may cause an upset stomach, particularly if eaten unripe (26). Summary Elderberries are a nutritious purple-blue berry popularly used as a natural remedy for cold and flu symptoms. Concord grapes are a healthy, purple-blue fruit that can be eaten fresh or used to make wine, juices, and jams. They’re packed with beneficial plant compounds that function as antioxidants. In fact, Concord grapes are higher in these compounds than purple, green, or red grapes ( 27 ). Though more research is needed, some studies show that Concord grapes and their juice may boost your immune system ( 28 ). For example, one 9-week study that had people drink 1.5 cups (360 ml) of Concord grape juice daily observed increases in beneficial immune cell counts and blood antioxidant levels, compared with a placebo group ( 29 ). Additionally, several smaller studies suggest that drinking Concord grape juice daily may boost memory, mood, and brain health ( 30 , 31 , 32 , 33 ). Summary Purple-blue Concord grapes may boost immunity, mood, and brain health, though more studies are needed to confirm this. Black currants are very tart berries with a deep, bluish-purple hue. They can be eaten fresh, dried, or in jams and juices. Black currants are especially high in vitamin C, which is a well-known and potent antioxidant. A single cup (112 grams) of fresh blackcurrant supplies more than two times the DV for this vitamin ( 34 ). As an antioxidant, vitamin C helps protect against cellular damage and chronic disease. In fact, some population studies note that diets rich in this nutrient may offer significant protection against heart disease ( 35 ). Additionally, vitamin C plays a key role in wound healing, your immune system, and the maintenance of your skin, bones, and teeth ( 23 , 36 , 37 ). Summary Blackcurrants are packed with vitamin C, a potent antioxidant that plays a vital role in your immune system and helps maintain healthy skin, bones, and teeth.
Damsons are blue plums that are often processed into jams and jellies. Prunes are a popular choice for digestive problems, including constipation, which is an ailment that affects an estimated 14% of the global population ( 39 ). They’re high in fiber, with 1/2 cup (82 grams) packing an impressive 6 grams of this nutrient ( 15 ). As a result, eating more prunes may increase stool frequency and soften your stools, making your bowel movements easier to pass ( 40 , 41 ). Plums also contain certain plant compounds and a type of sugar alcohol called sorbitol, which may help loosen your stools and promote more frequent bowel movements as well ( 42 ). Summary Prunes made from damson plums supply fiber, beneficial plant compounds, and the sugar sorbitol — all of which may help relieve constipation.
Blue tomatoes, also known as purple or Indigo Rose tomatoes, are grown to be high in anthocyanins ( 43 ). Their high anthocyanin content gives off a purple-blue tint ( 44 ). Several studies suggest that diets high in anthocyanin-rich foods may reduce inflammation, protect against heart disease, and promote eye and brain health ( 45 , 46 , 47 , 48 , 49 , 50 ). What’s more, blue tomatoes pack various other powerful antioxidant compounds typically found in regular tomatoes, such as lycopene ( 51 ).