When it comes to fruits, you can’t go wrong with blueberries. Read any article on foods for weight loss, heart health, brain health, or skin health, and you’ll find that blueberries always make it to the top 10. You don’t even need to peel or prep them. All you need to do is wash and eat these tiny fruits chockablock with antioxidants! Unsurprisingly, it can be tempting to binge on these delicious berries. They’re healthy, so it must be OK to have as much as you want to, right? Maybe not.
As per the USDA recommendation, most adults on a 2000 Cal diet need 2 servings of fruit daily.1 So half a cup (~ 75 g) of fresh or frozen blueberries or about 4 oz juice is the common daily serving size. For a normal healthy adult, eating a few too many blueberries, say a cup or a little more, should not be a matter of concern, especially if it is spread through the day. However, remember that these are not the only foods you eat in a day, and no one portion size suits all. Despite their antioxidant load and benefits for the brain and the heart, overeating blueberries may work against you. Here are the 4 possible side effects of eating too many blueberries.
1. Can Cause Digestion Problems
Eating too many blueberries can have uncomfortable digestive side effects. This is because of the fiber content in the fruit. A cup of blueberries contains 3.6 g fiber, which is not a lot. However, this is not the only source of fiber in your diet. If you anyway have a high-fiber diet, adding too many blueberries to it may cause bloating, stomachache, or diarrhea. This side effect will be more prominent in people who have digestive diseases like ulcerative colitis or Crohn’s disease. And while these berries have a lower natural sugar level than most fruits, having too many of them may still be a problem for those who suffer from fructose malabsorption – a condition where fruit sugars are not well digested.
2. May Increase Bleeding
If you are on blood-thinning medicines like warfarin or anti-platelet drugs like clopidogrel, you need to reconsider including blueberries in your diet. Blueberries have two components that have opposite roles on blood clotting. Vitamin K helps blood clotting, and the salicylates increase blood thinning.2
A cup of blueberries has 28 mcg vitamin K, which is not a lot, but the berries are probably not the only source of K in your diet.3 On the other hand, it is possible that the salicylates can compensate for the blood-clotting effect of the vitamin K and increase the effect of your medicines. Now which effect will be predominant also depends on other foods in your diet and the dosage of your medicine. This is why you need to find out from your doctor the ideal portion size of blueberries that would not interfere with the medication in your particular dose, or whether you need to give them a miss altogether.
3. Can Lower Blood Glucose Abnormally
Blueberries also have a significant effect in reducing blood sugar and increasing insulin sensitivity. They have been shown to reduce the blood glucose spike after a carb-rich meal by blocking the function of certain digestive enzymes. They can even slow down protein digestion.4 This might not be a good news for diabetics on medication since eating too many blueberries may further lower the blood glucose levels below normal. You must ask your doctor to tell you whether you should at all have blueberries and if you do, what the portion size should be.
4. Can Trigger An Allergic Reaction
If you are allergic to aspirin, you might well be allergic to blueberries, thanks to the salicylates. Every 100 g blueberries (all types of berries in fact) has 27.6 mg salicylates,5 which can be considered a concerning amount for people with salicylate intolerance. The allergy manifests as wheezing, asthma, rashes, or stomach pain.
Blueberries might be tasty, but they are not the only fruit you need to include in your daily fruit servings. Even 3 servings a week can do you a world of good.6 Try to switch it up and enjoy other berries and fruits. Remember, moderation is key!
|↑1||Dietary Guidelines 2015–2020. USDA.|
|↑2, ↑5||Swain, Anne R., Stephen P. Dutton, and A. Stewart Truswell. “Salicylates in foods.” J Am Diet Assoc 85, no. 8 (1985): 950-60.|
|↑3||Vitamin K. University of Maryland Medical Center.|
|↑4||Mcdougall, Gordon J., and Derek Stewart. “The inhibitory effects of berry polyphenols on digestive enzymes.” Biofactors 23, no. 4 (2005): 189-195.|
|↑6||Eat blueberries and strawberries three times per week. Harvard Medical School.|