The Sour Truth about Sweet Fruit

Why would a sugar found naturally in fruit be so poorly

tolerated by modern humans? It doesn’t make intuitive

sense, until we consider the scarcity and seasonality of fruit

until a few short decades ago. Like the casino of a Las Vegas resort, our modern food

complex has lost any sense of time, place, and season.

Within a single generation we have gained unprecedented

access to sweet fruit. A pineapple from the tropics, berries

grown in Mexico, and Medjool dates from Morocco are now

flown to our towns and cities so that they may line our

supermarket shelves all year long. These fruits are bred to

be larger, and contain more sugar, than ever before in

history.

We are frequently told that it’s okay—beneficial, even—

to consume “unlimited” fruit, but looked at through an

evolutionary lens, fruit (and particularly today’s cultivated,

high-sugar versions) may be uniquely adept at tricking our

bodies’ metabolisms. This is theorized to be an adaptivetemporary quality that helped us pack away fat so that we

might survive the winter. In fact, it is thought that our

ancestors developed red-green color vision for the sole

purpose of distinguishing a ripe, red fruit from a green

background—an evolutionary testament to the lifesaving

value of fruit for a hungry forager. Today, 365 days of highsugar fruit consumption is readying our bodies for a winter

that never seems to come.

What consequences of gorging on grapes and other

sweet fruit could there possibly be for our brains? A few

large studies have helped to shed some light. In one, higher

fruit intake in older, cognitively healthy adults was linked

with less volume in the hippocampus. This finding was

unusual, since people who eat more fruit usually display the

benefits associated with a healthy diet. In this study,

however, the researchers isolated various components of the subjects’ diets and found that fruit didn’t seem to be doing

their memory centers any favors. , Another study from the

Mayo Clinic saw a similar inverse relationship between fruit

intake and volume of the cortex, the large outer layer of the

brain.30 Researchers in the latter study noted that excessive

consumption of high-sugar fruit (such as figs, dates, mango,

banana, and pineapple) may induce metabolic and cognitive

derangements on par with processed carbs.

DOCTOR’S NOTE: WHEN YOU REALLY NEED TO RESTRICT FRUIT

People have a wide tolerance for carbohydrates, but for

diabetics, it’s pretty open-and-shut that sugar, even from

fruit, needs to be dramatically restricted. I have my diabetic

patients consume fruit in half-serving quantities—even a

single orange can spike the blood sugar into an

unacceptable range for hours after eating it. But all is not

without hope! Once insulin sensitivity is restored, exercise

has become a habit, and the system has had time to restore

energy balance and metabolic flexibility, unprocessed carb

sources can be reintroduced.

Fruits, however, do contain various important nutrients.

Luckily, low-sugar fruits are among the most concentrated

sources of these nutrients. Some examples include coconut, avocado, olives, and cacao (no, this does not mean that

chocolate is a fruit—but dark chocolate does have a myriad

of brain benefits and is one of our Genius Foods). Berries

are also great because not only are they low in fructose but

they are particularly high in certain antioxidants shown to

have a memory-boosting and anti-aging effect. The Nurses’

Health Study, a long-running dietary survey of 120,000

female nurses, found that those who ate the most berries had

brains that looked 2.5 years younger on scans.31 In fact,

while a recent analysis of the literature found no association

between overall fruit intake and reduced dementia risk,

berry consumption was the sole exception. Berry nice!

A Call to Action

Every year, billions of dollars are spent to market junk foods

to the American people. But more than simply buying ad

space in magazines or on TV, these juggernaut companies

regularly fund studies to downplay the role of junk food in

the public obesity crisis. The New York Times recently

exposed scientists involved in a leading soda giant’s

initiative to shift the focus in the global obesity and type 2

diabetes epidemics from diet to laziness and lack of

exercise. An executive of the group was quoted as saying:

Most of the focus in the popular media and in the

scientific press is, “Oh they’re eating too much, eating

too much, eating too much”—blaming fast food, blaming sugary drinks and so on. And there’s really virtually no compelling evidence that that, in fact, is the cause.

While exercise is vital to the health of the brain and

body, study after study has shown it to be only minimally

impactful on weight compared with what people consume.

Fitness enthusiasts know that “abs are made in the kitchen,”

but for many of those who are overweight and obese, a

statement like the above only perpetuates the confusion.

This sets up a trap for society’s most vulnerable, paving the

way for cognitive dysfunction and an early death. This is

not an exaggeration: for the first time, our eating habits are

killing more Americans than our smoking habits. In fact,

the latest figures, published in the journal Circulation,

suggest that nearly two hundred thousand people die each

year from diseases driven by sugar-sweetened beverages

alone. That is seven times the number of people killed by

global terrorism in 2015.

And speaking of smoking, let’s look for a second to the

historical awareness of the link between cigarettes and lung

cancer. It took decades for enough “proof ” to show up in

the medical literature to convince physicians that cigarettes

were a major driver of soaring lung cancer rates, even

though the disease had been “very rare” prior to the

ubiquity of smoking in the mid-twentieth century. And who

can forget the cringe-worthy ads from the 1940s (easily

Googleable) featuring doctors blatantly endorsing

cigarettes? As recently as the 1960s, two-thirds of all US

doctors believed the case against cigarettes hadn’t yet been

established, despite smoking being recognized as a leading cause of the lung cancer epidemic two decades prior.