Our taste buds evolved to make sure we eat nutritious, calorie-dense food, and avoid rancid, toxic foods. A layer deeper, we evolved cravings to look forward to future taste bud satisfaction, motivating us to leave the cave and chase down a mammoth, dig up tubers, or brave a honey-filled beehive.
Our tastes evolved to point us in the right direction and nudge us toward the right plants and animals to eat, regardless of how those plants and animals felt about the matter. Whereas we evolved to find meat, potatoes, and honey appealing, fruits are different in that they evolved to be appealing to us. Fruit is unique in its appeal. Unlike with other human foods, the evolutionary action belongs to the fruit, not to the human.
Fruits are no different than humans in their desire to procreate and pass on their genes, but fruits rely on energy-seeking animals to carry out their reproductive desires. A fruit's best bet of passing on its seed far-and-wide is for a roaming animal to eat the fruit, continue on its way, and excrete the undigested seed(s) in its feces a few hours or days later. Once excreted, the seeds could grow into future fruit-bearing trees and bushes, fertilized by the nitrogen-rich feces of the animal. Primates and early humans were perfect "carriers" for the seeds of fruits, so fruits evolved to be sweet and taste especially delicious to us, compelling us to great heights in order to carry out their wishes.
While today's selectively bred bananas, grapes, and oranges are mostly without their seeds, open a banana in the wild and it's likely to be full of seeds. In the same way that we've bred fruits to be seedless, we've also bred them to be sweeter. Today's most popular fruits, while deliciously sweet and easy to eat, are about as similar to wild fruits as chihuahuas are to wolves. Hundreds of years of selective breeding have produced fruits that are optimized for taste and yield, but not necessarily for nutrition or health. The fruits lower in sugar and more similar to their wild ancestors are usually the healthiest and the ones we should be seeking out. That doesn't mean that we should spend an hour eating a wild banana and picking out all the seeds, but it does mean we should be cognizant of which fruits have been most selectively bred for sweetness.
Fruit is an important part of many people's diet. Although fruit is not an essential part of a healthy diet, some fruits can be an important source of nutrients and polyphenols (antioxidants). However, other fruits have more in common with candy than they do with healthy plant foods. In fact, two of the most consumed fruits in the US also happen to be the two least healthy. They're popular because they taste like juicy, crunchy candy but have been marketed as health foods.
There are three main positive qualities that make certain fruits healthy:
1. Micronutrients (vitamins and minerals)
2. Antioxidants
3. Fiber
And there are a couple negative qualities we should watch out for:
1. Sugar (specifically, fructose)
2. Blood sugar impact (glycemic load)
Because fruit tends to affect blood sugar levels less than most other carbohydrate-sources like rice, bread, and pasta, most fruits makes a great snack, and can be especially delicious–and result in an ever lower blood sugar impact–when combined with a protein/fat like yogurt, coconut, and nuts.
Of the common fruits, even the worst blood sugar offenders have less than a third of the blood sugar impact as the same amount of "healthy" carbohydrates like oats and whole wheat bread [1]. Because the majority of fruits fall within the safe range of blood sugar impact for most people, we're not going to consider glycemic index as a variable when determining the healthiest and unhealthiest fruits.
Similarly, most fruits have between 1-3 grams of fiber per 100 grams, not enough of a difference to be a significant part of our analysis.
Unlike glycemic index and fiber, there is a lot of variability in the amount of nutrients, antioxidants, and fructose sugar from fruit to fruit. The most nutritious fruit has 9 times as many vitamins and minerals as the least nutritious, the most polyphenol-rich fruit has over 60 times the antioxidants compared to the least polyphenol-rich, and the sweetest fruit has about 5 times as much fructose sugar as the least sweet.
Let's chart the most common fruits in a way that allows us to see the most important qualities–nutrient density, antioxidants, and fructose sugar–all at once:
Lots to digest here!
As you can see, kiwis are the most nutritious fruit gram-for-gram, with 100 grams (one large kiwi) providing over 9%of your entire day's micronutrient needs... and that's without the skin. The skin contains even more beneficial fiber and Vitamin C (and tastes great), making kiwis far and away the leader in nutrition.
Pineapples, while moderately high in sugar, are second in terms of nutrients, providing about 7%of your daily nutrient needs. Blackberries, raspberries, and strawberries are probably the most well-rounded fruits, with very low sugar and high amounts of nutrients and antioxidants.
Blueberries, while not being especially full of nutrients, are incredibly high in antioxidants. You can't really go wrong with a berry, and may want to mix it up between different berries to get a variety of different antioxidants. A handful of raspberries here, a handful of blackberries there.
Bringing up the rear are apples and pears, which are bred for sweetness, not nutrients. In addition to apples and pears, mangos, pineapples, bananas, grapes, and cherries are all fruits that are especially high in fructose sugar. The dose makes the poison, so while a little bit won't hurt as part of a healthy low-sugar diet, it can be easy to overindulge.
While it is said that, "An apple a day keeps the doctor away," modern apples (and pears) should be seen as occasional indulgences, not prescriptions for better health. "A kiwi a week for the health you seek,"may be a better guide.
