So, evidently I'm now taking requests as a friend of mine, Rich, asked me to do a post about fruit and how it affects diet. I know what many of you are thinking: "Fruit unhealthy? Crazy talk! Why would he even question fruit?" After all, we've all heard the colloquialism: "An apple a day keeps the doctor away." Fruit being a healthy food has become common speak, or part of the dietary zeitgeist. But is it?
Since this blog is also about nutrition and health in general, and not solely about paleo or evolutionary health and nutrition, I think that this is a great opportunity to help a friend, and dispel some of the myths about fruit relative to a healthy diet.
Let's start with the question: Is fruit healthy? The answer to that it depends on the fruit, and the person eating it. Fruits can be wonderfully nutritious as far as plant foods are concerned, but as you'll see not all fruit is created equal. For example, berries tend to be the most antioxidant rich of fruits, and these include but are not limited to: Blueberries, black berries, raspberries, acai, elderberries and cranberries. Apples, strawberries, peaches and plums have respectable amounts of antioxidants as well. (1)
Some fruits are best avoided or eaten in moderation and should be treated as more of a desert due to their high fructose content and high glycemic index. For example, one banana has the same amount of sugar as a Hershey bar. One serving of grapes (151g) has more sugar than 12 Pixy Stix straws, or a Kit Kat. (2, 3) Think of high sugar fruit as having a cookie or a cupcake every once in a while. Poor choices from a sugar/GI/carb perspective include bananas, apples, dates, grapes, mangoes, pineapple, and persimmon. (4)
(Lay off those persimmons Rich)
An explanation of why sugar/fructose can play a problematic role, watch this: http://www.youtube.com/watch?v=dBnniua6-oM
Your body doesn't discern the difference between sugars whether from an orange, an apple, a watermelon, a bon bon, or a kit kat. They all affect insulin spikes, hunger, fat storage and insulin resistance the same. But for some reason there's this idea that fruit has some inherent "good" version of fructose/sugar and fruit reverence amongst some vegans and vegetarians can reach almost cult-like proportions if talking with the right fool. Personally, I don't suffer fools very well.
So, what happened? How could such a staple of our ancestral diet have gone so awry as to become bad for us? Well, in a very similar way to how we screwed up much of the food we consume, we've altered fruit since the Neolithic advent of agriculture.
How you ask?
First, just by gathering fruit, humans (and all animals for that matter) typically select the largest, most colorful, and most palatable versions of said fruit. Apples for example, have gotten much larger and sweeter over time. Examples of this process are found throughout the world with all edible vegetation such as Corn, Rice, Oranges, Tomatoes, etc. Corn, for example, started off as a kind of grass (Teosinte) and through generations of selection, became maize, or what we call "corn". (5) Most fruit, as shown in the archaeological record, were much more fibrous, and as such, self-limiting in it's density to sugar ratio.
Secondly, agriculture, especially modern agri-business have increased this selection process by production volume in their never-ending quest for yield and profit. He who has the largest and sweetest sugar-filled apples garners the most money.
Lastly, big agribusiness tampers with the DNA of many fruits to make them resistant to certain toxic pesticides, and to develop sweeter strains.
So is fruit always unhealthy? No. For those without any metabolic derangement such as obesity, diabetes, or thyroid disregulation, fruit can be fine. But again, treat it as a treat. If your trying to lose weight, I'd consume fruit in moderation, and keep my overall carb intake to around 100 grams. For maintenance, I'd keep my carb intake to around 150-250g, without a steep performance bias.
If someone was an endurance athlete or an athlete with a performance bias, I'd up the carbs to a level that facilitates performance without eliciting fat storage. That's something that you're going to have to determine with some n=1 experimentation. But based on your activity level, it could be anywhere from 200-400g. Everyone's different in that regard.
If someone were an obese or sedentary person for example, a lower carb approach might be more appropriate, and I'd avoid ingesting too much fruit in an effort to reduce carb intake so that we can get that person to a leaner, more fat-burning (burning fat preferentially as ketones) vs. carb-burning machine.
As you can see, the amount of fruit that's "Okay" is largely dependent on the patient. If one is eating a nutrient-dense diet, most likely he's already eating plenty of meat and fat which are incredibly satiating, and uninclined to take in too many carbs anyway. Once one's reached a good level of metabolic homeostasis and/or leaned out, adding more fruit to the diet might be appropriate (or perhaps some low GI tubers). But, as I've said over and over again, it's better to get most of your carbs from vegetables if possible, as they are equal or greater in nutrient density, antioxidants, as fruits with less insulinogenic effects.
And Rich, to answer your question: I'd not indulge in eating 2 lbs of grapes in one sitting or an entire watermelon very often, but as long as you keep such binges acute and rare, rather than chronic and often, you're probably gonna be okay. (if not ab-less.)