Everyone inherits 2 copies of a taste gene called TAS2R38
Inheriting two copies of the unpleasant taste gene provides a "ruin-your-day level of bitterness" to foods like broccoli and sprouts, they say.
It could explain why some people find it difficult to include enough vegetables in their diet, they suggest.
The gene may also make beer, coffee and dark chocolate taste unpleasant, reports BBC.
In evolutionary terms, being sensitive to bitter taste may be beneficial - protecting humans from eating things that could be poisonous.
But Dr Jennifer Smith and colleagues from the University of Kentucky School of Medicine say it can also mean some people struggle to eat their recommended five-a-day of fresh fruit and vegetables.
Everyone inherits two copies of a taste gene called TAS2R38. It encodes for a protein in the taste receptors on the tongue which allows us to taste bitterness, the report said.
People who inherit two copies of a variant of the gene TAS2R38, called AVI, are not sensitive to bitter tastes from certain chemicals.
Those with one copy of AVI and another called PAV perceive bitter tastes of these chemicals, but not to such an extreme degree as individuals with two copies of PAV, often called "super-tasters", who find the same foods exceptionally bitter.
The scientists studied 175 people and found those with two copies of the bitter taste PAV version of the gene ate only small amounts of leafy green vegetables, which are good for the heart.
Smith told medics at a meeting of the American Heart Association: "You have to consider how things taste if you really want your patient to follow nutrition guidelines."
The researchers hope to explore whether using spices could help mask the bitter taste and make vegetables more appealing for people who are hard-wired to dislike certain varieties.