High in fiber, potassium and vitamins A and K, blueberries pack a nutritional punch. Unfortunately, in some cases they can have side effects, including gastrointestinal distress, hypoglycemia and an increased risk of bleeding if you are taking some prescription medications. If you're healthy, eating blueberries as part of a balanced diet is not likely to cause side effects. However, if you have an underlying health condition, check with your doctor before adding them to your diet.
Blueberries contain very high amounts of salicylates -- the active ingredient in aspirin which is also found naturally in many plants -- which can cause side effects in people who are sensitive to salicylates. For those who can't tolerate salicylates, blueberries might cause a rash, headaches or a host of gastrointestinal symptoms, including nausea, vomiting, reflux, bloating, gas, diarrhea and constipation. Blueberry juice is especially high in salicylates. Eating blueberries in small amounts may ease some of the pain and discomfort associated with the ingestion of salicylates.
Blueberries contain 29 micrograms of vitamin K per one-cup serving, making them a "medium" vitamin K food. Vitamin K performs a number of important functions in the body, including regulating blood clotting and maintaining bone density. People who take prescription blood thinners are generally encouraged to keep bloodstream levels of vitamin K the same from day to day. Suddenly increasing or decreasing your intake of foods rich in vitamin K, such as blueberries, without asking your doctor to make changes to prescription blood-thinner dosages can lead to an increased risk of bleeding.
Hypoglycemia from Blueberry Leaves
If you have been diagnosed with diabetes, taking blueberry leaves as a supplement can cause a dangerous drop in blood-sugar levels. Always check with your doctor before adding any supplements, including blueberry leaves, and monitor your blood sugar carefully. Eating blueberries, the fruit, is likely safe for people with diabetes and a 1-cup serving of blueberries contains 21 grams of carbohydrates.
Adding Blueberries to Your Diet
Unless you have an underlying health condition, blueberries are unlikely to cause serious side effects. In fact, when eaten in moderation, blueberries can play an important role in a balanced diet. According to ChooseMyPlate.gov, adults should aim for between one and a half and two servings of fruit, such as blueberries, each day. Consider adding blueberries to hot or cold breakfast cereals, or blend them into a smoothie for a quick snack on the go. You can also toss blueberries in salads, bake them in desserts, or add them to soups and side dishes.