Blueberries: benefits, nutrition facts and side effects

Blueberries are a reservoir of antioxidants. These antioxidants protect the body from damage caused by free radicals present in the body. Free radicals are unstable molecules that can damage the DNA and various cells in the body, leading to organ damage, ageing and even cancer.

The most common antioxidant compound present in blueberries is flavonoids. Anthocyanins, a type of flavonoid, is responsible for providing blueberries with all the health benefits. 

In a study published in the Journal of Carcinogenesis in the year 2007, 168 people were given one litre of blueberry and apple juice for four weeks. After four weeks, the researchers found that the damage caused to the DNA by oxidative stress reduced by 20%. They further concluded that the antioxidants in blueberries can neutralize the free radicals which damage DNA.

The oxidative stress created by the body not only damages the cells but also oxidises the low-density lipoprotein (LDL), also known as the bad cholesterol. Once oxidised, this bad cholesterol can lead to a number of heart diseases. 

A study published in The Journal of Nutrition included 48 obese people who were fed 50 grams of blueberries on a daily basis for eight weeks. After eight weeks, these people presented with 27% less LDL oxidation in their body. 

The researchers concluded that antioxidants present in blueberries reduce the levels of oxidised LDL in the body, thus protect the heart from various diseases.

In addition to reducing bad cholesterol which can lead to problems like atherosclerosis and coronary artery disease, blueberries may also reduce the risk of a heart attack.

A study that was published in the journal Circulation and included around 93,600 women in the age group of 25 to 42 years, concluded that women who consumed anthocyanins the most had 32% reduced risk of having a myocardial infarction (commonly known as a heart attack) compared to those who took very little or no anthocyanins in their diet.

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Scientists have found that blueberries can prove beneficial for people with high blood pressure which otherwise can lead to major health issues including stroke and heart diseases. In a study published in The Journal of Nutrition, 48 obese people with a high risk of heart diseases were given 50 grams of blueberries regularly for eight weeks. After eight weeks, the researchers found that there was a 4% to 6% reduction in their blood pressure.

The free radicals in the body speed up the ageing process which not only affects the body but also the brain. Scientists believe that oxidative stress can accelerate your brain's ageing process. 

In a small study published in The Journal of Agricultural and Food Chemistry, it was seen that after consuming blueberry juice for 12 weeks, there was an improvement in cognitive abilities as well as other brain functions. 

Another large scale study published in the Annals of Neurology—conducted from 1995 to 2001—which included around 16,010 people, stated that blueberries have the ability to delay mental ageing by up to 2.5 years.

Blueberries contain moderate amounts of sugar in them. Despite this, blueberry juice and extracts have proven abilities to control blood sugar levels.

In a double-blind clinical study conducted in the year 2006, researchers found that the anthocyanins present in blueberries increase insulin sensitivity in the body and also help in glucose metabolism in the people suffering from diabetes. Thus keeping the blood sugar levels controlled.

Another study published in The Journal of Nutrition in the year 2010, stated that blueberry smoothies can help in improving insulin sensitivity in obese people whose bodies do not respond to insulin accurately.

Insulin is a hormone released by the pancreas in the body which generally helps in keeping the levels of blood sugar within the normal range.

Although anyone can get a urinary tract infection (UTI), the condition is more prevalent in women. People with recurrent UTIs are prescribed cranberry juice for preventing the infection. 

Studies have revealed that blueberries are as potent as cranberries in treating and preventing UTIs in women. An article published in the New England Journal of Medicine stated that cranberry and blueberry juices have anti-adhesive properties which prevent UTI-causing bacteria, E. coli, from sticking to the wall of your bladder.

People who undergo any cardiac treatment—for instance, cardiac stent placement (angioplasty)—need to stay on blood thinners for a long time. While taking these blood thinners, the person needs to maintain the exact levels of vitamin K in their body on a daily basis as vitamin K is responsible for regulating blood clotting.

Since blueberries are a good source of vitamin K, an excess of these can cause harm to the people on blood thinners. Excess consumption of blueberries in patients on blood thinners can lead to abnormal clotting in the blood.

Similarly, if the person has been consuming the berries for a long time and then quits all of a sudden, it can increase the risk of bleeding in them.

As described above, blueberries have the potential to reduce blood sugar levels and thus can prove beneficial for people with diabetes. However, it can be harmful to those who have already been taking medications for diabetes, as for them, blueberry can bring a dangerous drop in blood sugar levels which is medically called hypoglycemia. A diabetic person must consult their doctor before consuming fresh or frozen blueberries or supplements.

Blueberries are rich in salicylates, which is the main ingredient found in aspirin. People who are sensitive to salicylates may present with allergic reactions such as a skin rash, headache, nausea and vomiting, bloating, diarrhoea or constipation.