A Harvard researcher is sounding the alarm on three fruits that might be doing more harm than good. Dr. Nick Norwitz, a metabolic health expert, claims mangoes, grapes, and jackfruit are packed with so much fructose they could be sabotaging your health. Too much of these sugary fruits, he warns, could even raise your risk of obesity and cancer.
Mangoes top the list, with a full-sized fruit delivering around 30 grams of fructose—more than double what you’d get from an apple. Grapes pack a similar punch, making them one of the highest-sugar fruits you can eat. Jackfruit, a tropical favorite, is loaded with natural sugars that could overwhelm your metabolism.
Norwitz points to research suggesting excessive fructose can wreak havoc on the intestines and liver. A 2021 study found mice fed high-fructose corn syrup developed longer intestinal villi, leading to increased fat absorption and weight gain. Their bodies were primed to store more fat, and when paired with a high-fat diet, the results were even worse.
There’s also a worrying link between fructose and cancer. The same study found that fructose could fuel the survival of cancerous cells in the colon. The more fructose in the system, the longer these toxic cells lingered, potentially accelerating tumor growth.
Of course, not all fructose is created equal. The study in question focused on high-fructose corn syrup, which is processed differently than natural fruit sugars. That said, Norwitz argues that even “natural” fructose in excess could have similar effects over time.
The debate over fruit and sugar isn’t new, but blindly assuming that all fruit is healthy might be a mistake. Norwitz warns that sweeping generalizations—like “fruit is always good”—ignore real metabolic concerns. Different fruits interact uniquely with different people, and for some, cutting back on sugary varieties might be a smart move.
Fruits like berries, avocados, and citrus have lower sugar content and higher fiber, making them a safer bet. If weight control or metabolic health is a concern, it may be worth reconsidering those giant fruit bowls filled with grapes and mango slices.
For years, fruit has been marketed as nature’s candy—healthy, wholesome, and guilt-free. But when it comes to high-fructose varieties, that “candy” might come with unintended consequences.
Five Fast Facts
- Mangoes are the national fruit of India, Pakistan, and the Philippines.
- Grapes have been cultivated for over 8,000 years and were one of the first domesticated fruit crops.
- Jackfruit is the largest tree-borne fruit in the world, sometimes weighing over 80 pounds.
- Fructose was first identified as a distinct sugar in 1847 by French chemist Augustin-Pierre Dubrunfaut.
- The average American consumes over 40 pounds of high-fructose corn syrup per year.
