The second most commonly consumed vegetable in the United States is … a fruit. Americans eat around 12.7 pounds of tomatoes per capita each year, a total that trails only potatoes. But while tomatoes are widely viewed as vegetables, botanically, they’re fruits. They’re not alone—cucumbers, peppers, olives, eggplant, zucchini, avocados and pumpkins are botanical fruits, too.
What is a Fruit?
So why is pumpkin a fruit? Why is tomato a fruit? Why is cucumber a fruit? Botanists base classification like these not on a food’s flavor, nor on the role it plays in a diet, but on plant anatomy.
Botanically, a fruit is the ripened, seed-containing ovary of a flowering plant. Plants produce fruits as a reproductive strategy—animals consume fruits then deposit their seeds in different locations. That sets fruits apart from vegetables, which are part of a plant’s body, not something that plant produced to be consumed as a way to spread seeds.
Such distinctions matter to botanists and occasionally to tax collectors—U.S. courts once ruled that tomatoes were subject to a vegetable tax even though they’re not technically vegetables, but should they matter to the rest of us?
Are there notable nutritional differences between vegetables and fruits, or any other reasons for the average eater to worry about whether tomatoes, cucumbers, peppers and the like fall into one of these produce categories or the other?
Bottom Line Health asked Stanford University diet and nutrition expert Christopher Gardner, PhD, to weigh in on the topic.
The nutritional value of vegetables vs. fruits
Fruits are good for us, but vegetables are, on average, better:
- A close look at the ten most commonly consumed fruits and the ten most commonly consumed vegetables in the United States reveals that the vegetables contain less sugar per calorie. Vegetables contain about10.4 grams [g] of sugar per 100 calories versus 17.3 g for the fruits.
- Vegetables have more fiber (7.1 g versus 3.8 g for the fruits.
- Vegetables also have a higher aggregate nutrient density index (ANDI)—227.5 versus 74.5 for fruit. ANDI is a measure that attempts to distill a food’s overall nutritional content down to one number.
These aren’t firm rules: There are dramatic differences in sugar, fiber, and nutritional content from fruit to fruit and from vegetable to vegetable. But overall, it’s apparent that popular vegetables are somewhat better for us than popular fruits—an advantage that only increases if potatoes, a nutritional laggard by vegetable standards, are excluded.
In fact, there’s reason to suspect that veggies’ nutritional advantage might convey a meaningful long-term health advantage. While both vegetable consumption and fruit consumption have been linked to lower mortality rates by numerous studies, a 2018 review of 13 large-scale studies on the subject found that vegetable consumption seems to be somewhat more strongly linked to lower mortality rates than fruit consumption. Again, it’s worth reiterating that both vegetables and fruits are good for us, and most Americans need more of both in their diets. But of the two, vegetables seem to be a bit more valuable when it comes to living a long life.
What does all of this mean for the fruits that are generally thought of as vegetables? Nutritionally, these vegetables that are fruits often fall in between the average vegetable and the average fruit, but in many key ways, they tend to be closer to the vegetable side of things.
Consider the three vegetables that are fruits that are most widely consumed in the US—tomatoes, cucumbers and green bell peppers. Each of these has less sugar, more fiber, and a higher ANDI than the average of the 10 most popular fruits:
- Tomatoes contain 14.6 grams of sugar per 100 calories, 6.6 grams of fiber and have an ANDI of 186.
- Cucumbers contain 11.1 grams of sugar, 7.6 grams of fiber, and have an ANDI of 87.
- Green bell peppers contain 12 grams of sugar, 8.5 grams of fiber and have a stellar ANDI of 371.
All three of those fiber figures and two of the three ANDI scores would look more at home on a list of vegetables than on a list of fruits. The sugar stats are somewhat less clear cut.
Or consider olives—botanically, they’re fruit, but they contain an extremely low 0.14 grams of sugar per 100 calories, less than 1 percent as much as the average for the top-ten most consumed fruits.
If a food is generally treated like a vegetable in terms of how it’s included in diets, and its nutritional profile is comparable to that of vegetables, then those of us who aren’t botanists should probably continue thinking of it as a vegetable.
Outlier: Avocados are another botanical fruit that’s often considered a vegetable, but they’re not particularly like other fruits or other vegetables. They really deserve to have their own nutritional category. Avocados are extremely low in sugar, even compared to the average vegetable—just 0.4 grams per 100 calories. They also contain much more fat than is common for a fruit or vegetable, with 9.2 grams per 100 calories. Fortunately, an avocado’s fat is largely heart-healthy unsaturated fat.
The sugar question
People sometimes wonder “Is the high sugar content of fruit bad for us?” Fruits can contain significant amounts of sugar, as noted above, and it’s no secret that excessive consumption of sugar can lead to health issues, such as weight gain and increased risk of cardiovascular disease. Fortunately, the sugar in fruit is not linked to negative health or weight outcomes for most people. The types of sugar that fruit contains and the way the body typically processes it is significantly different from the added sugars found in processed foods. Any health downsides of fruits’ sugar are more than offset by the health advantages offered by fruits’ high fiber content and nutritional value.
That said, the sugar in fruit can potentially be problematic for diabetics and prediabetics. They still can eat fruit, but they should speak with their healthcare providers about how to do so without causing health complications.
Modifying the vegetable vernacular
Several health-focused organizations, including the U.S. Dietary Guidelines Advisory Committee, have quietly made a change in recent years. They’ve begun using the phrase “vegetables and fruits” in place of the more familiar “fruits and vegetables.” They’ve done this for two reasons. First, arranging commonly paired words in an unconventional order causes readers’ brains to slow down slightly and pay a bit more attention to the message being conveyed. In this case, the message is that Americans need more vegetables and fruits in their diets. Moreover, positioning the word vegetables first adds a bit of emphasis to veggies. The majority of Americans don’t get enough vegetables or enough fruits in their diets, but they’re especially likely to fall short with vegetables, so it’s probably for the best that botanical fruits like tomatoes, cucumbers and peppers can be included on the vegetable side of the ledger when we tally up our daily produce consumption, whatever the botanists might think.
*All nutritional content data in this article are per 100 calories consumed, not per fruit or vegetable.
