A Harvard researcher has claimed three popular fruits could be harmful to your health and cause you to gain weight.
Dr Nick Norwitz, a metabolic health researcher, claims the high sugar content in certain fruit can be metabolically harmful and may even increase the risk of developing cancer.
He took aim at mangoes, grapes and jackfruit for having high levels of fructose – natural sugars – compared to other fruits, which can cause ‘damage to the small intestines as well as liver’.
‘The blanket statements that fruit is “natural and therefore healthy” and “contains sugar and therefore unhealthy” are both harmful oversimplifications,’ he told Fox News.
‘Different fruits have different properties that interact with unique features of individuals.’
Dr Norwitz said mango has the highest levels of fructose – with about 30 grams in a full-sized mango in comparison to apples that only have 12.5 grams.
He cited a 2021 study published in Nature that found evidence of excessive consumption of fructose to a greater risk of obesity and related cancers, such as colorectal cancer.
However, that study looked at mice fed high fructose corn syrup, which is different from fructose found naturally in fruits, as it contains no corn starch and glucose.
Dr Nick Norwitz, a researcher-educator specializing in metabolism, claims that the high fructose content in fruits can be harmful
Researchers discovered mice who were fed high-fructose corn syrup for four weeks had the villi (fingerlike projections that absorb nutrients from food) inside their small intestines to be about 40 percent longer than their counterparts.
Those fed high-fructose corn syrup also gained significantly more weight and fat mass.
The scientists concluded fructose improved the survival of cells in the villi which caused it to lengthen.
With a high number of cells and longer villi, the body would absorb more nutrients. This could lead to increased fat absorption and weight gain when combined with a high-fat diet.
The scientists also examined the effects of fructose on colorectal cancer cells and discovered that it could increase tumor growth by helping the toxic cells live longer in the body.
While some studies suggest that fructose can cause damage, a 2014 literature review by National Institute of Medicine found that fructose does not have specific effects on the body that can cause weight gain compared with eating sugar from other sources.
In fact, experts at the the American Heart Association, point out that mango has more than 20 vitamins and minerals, including high doses of vitamins A and C, high fiber content and tons of antioxidants that are ‘beneficial for colon cancer prevention, heart disease and weight control.’
Fruits in general are also widely beneficial for regular bowel movements and digestion due to their high fiber content and is packed with vitamins that help improve eye health, boost immune system through antioxidants and regulate blood pressure.
Dr. Norwitz named mango as the highest fructose containing fruit – with about 30 grams of fructose in a full-sized mango
The Harvard and Oxford University graduate explained the negative effects of high fructose consumption
Fructose is a sugar found naturally in fruits, some vegetables and honey. It is also commonly added to processed foods in the form of high fructose corn syrup.
Manufacturers use high fructose corn syrup to make sugar-sweetened beverages and ultra-processed foods sodas, breakfast cereals, dairy products such as yogurts and candies.
After mangoes, Dr Norwitz then noted that jackfruit has around 15.2 grams of fructose in a cup as compared to a cup blueberries which only has 7.6 grams.
The fruit has become incredibly popular in recent years as a plant-based meat alternative due to its texture being remarkably similar to pulled meat.
However, those suffering from diabetes or are at risk of having low blood sugar levels may be advised to steer clear of jackfruit.
A 2021 peer study published in the Scientific World Journal discovered that jackfruit extract may increase insulin levels and significantly lower blood glucose levels – creating danger for those with fluctuating sugar levels.
Researchers found that mice who had been fed extract from jackfruit leaves had elevated insulin levels from 10.8 to 19.5 and reduced blood glucose levels from 200 to 56 than others who had eaten a control diet.
The scientists concluded that that jackfruit leaf extract contains flavonoids that may help prevent cell death in the pancreas, which is the organ that produces insulin, therefore increase the production of insulin the body and reduce blood sugar.
Sudden decrease in blood sugar can cause difficulty concentrating, dizziness, chest pain and seizures. In the long run, it can also cause brain damage and sometimes, death.
Despite this, jackfruit is known to be good source of vitamin C, which is a powerful antioxidant that is essential for a healthy immune system.
They are also known to produce substances called phytochemicals (plant-based chemical compounds), such as flavonoids, saponins and tannins that have cancer-fighting benefits, such as preventing cancer cells from forming in your body.
Even though it has gained reputation as a replacement for pork or chicken in many main dishes, jackfruit cannot compete with these animal products in terms of protein.
One cup of raw jackfruit has less than three grams of protein while a cup of typical everyday meats such as chicken have 38 grams.
Dr Norwitz then noted that jackfruit is extremely harmful to the body
Regardless of color, grapes have 12.3 grams of fructose per cup
Lastly, the metabolism expert warned of the dangers of grapes due to their high sugar content.
Regardless of color, grapes have 12.3 grams of fructose per cup as compared to a banana with just 5.7 grams of fructose.
Eating too many grapes at once can cause the body to not absorb fructose efficiently and lead to bloating, gas and stomach upset, especially if eaten on an empty stomach.
Additionally, the tannins in grapes can also irritate the stomach lining, potentially causing discomfort and diarrhea in some people.
But previous research has shown that grape consumption supports heart health and improvements in memory.
Some lower-fructose fruits include berries, kiwi, citrus fruits and non-sweet, low-carb fruits like coconut, avocado and olives.
The United States Department of Agriculture recommends that adults eat 1.5 to 2 cups of fruit per day
