Thursday, December 10, 2009

Artificially sweetened beverages: Is it nice to fool Mother Nature?

David Ludwig, MD, PhD, director of Children’s Optimal Weight for Life
Program, just published a commentary in JAMA expressing concern about the
widespread use of artificial sweeteners in soft drinks. Below, he offers
some insight about why humans naturally crave sweetness, and the potential
danger of confusing our ancient biological pathways of hunger and satiation
with fake sugars.

Ever since our distant ancestors crawled out of the ocean, animals have been
trying to eat plants. In this conflict, animals would seem to have a
distinct advantage: we can move about, they can’t. But plants are by no
means defenseless against our predations. They protect themselves with
thorns, bark and tough fibers; stash their starches in tubers that are
difficult to digest (at least when uncooked); encase their most prized
possessions, high energy nuts and seeds, in impervious shells; and lace
their leaves with bitter, toxic chemicals.

In fact, plants have long taken advantage of animals to help them reproduce.
To entice us to serve them, plants have created seed-bearing fruits and
infused them with sugar, the gold standard of energy metabolism. Sugars
constitute the building blocks of all carbohydrates, rich in available
energy and used by every cell in the body. Plants have also loaded fruits
with other vital nutrients, including vitamins, minerals and water, to keep
helpful animals alive and well. In contrast to most other parts of the
plant, fruit is highly nutritious, safe and easy to eat. For this reason,
plant-eating animals (including humans) have come to associate sweetness
with goodness and evolved an innate preference for all things sweet.

Consumption of sugars in their natural forms tends not to cause health
problems because plants dispense with the minimum amount of calories
necessary to keep seed-spreading animals coming back for more, but not
enough to cause obesity. An 8-oz apple contains fewer calories than a 2-oz
pretzel. Problems arise when sugars are refined, concentrated and added to
the food supply in massive amounts. Sugar-sweetened beverages merit special
mention, because sugar in liquid form seems to escape notice by the body’s
calorie-detecting apparatus.

Modern science, which gave us refined sugars like high fructose corn syrup,
has proposed a novel solution to the obesity epidemic: artificial
sweeteners. These compounds stimulate taste receptors at hundreds to
thousands of times the potency of natural sugars, producing intense
sweetness at trace concentrations. (Curiously, the artificial sweetener
sucralose was discovered after a young Indian chemist in London was told to
test a potential insecticide; due to the language barrier, he misunderstood
and proceeded to taste the newly synthesized compound, finding it
overwhelmingly sweet.)

With growing attention to the adverse effects of sugar-sweetened beverages,
consumption of artificial-sweetened beverages has increased dramatically.
Indeed, some industry analysts predict that sales of these “diet” drinks
could eventually exceed those of sugar-sweetened beverages. Clinical trials
show that artificial-sweetened beverages may produce short-term weight loss
when substituted for their calorie-containing counterparts, but these
effects have never been tested for more than a few months. One reason for
concern is that consumption of artificial-sweetened beverages produces an
evolutionarily unprecedented dissociation between sweet taste and calorie
intake that might confound the regulatory system designed to control hunger
and body weight.

In support of this possibility, a recent study found that rodents fed the
artificial sweetener saccharin lost the ability to accurately regulate
calorie intake and gained weight. Another concern is that habitual
consumption of artificial-sweetened beverages may “infantilize” taste
preferences, especially among children. Compared to the hyper-intense
sweetness of these beverages, fruit may seem bland and vegetables may seem
inedible, adversely affecting overall diet quality. Indeed, two
observational studies have linked artificially sweetened beverage
consumption to higher risk for obesity, cardiovascular disease and type 2

Humans have always savored sweetness, and until recently, our sweet tooth
caused limited harm. However, high consumption of sugar-sweetened beverages
throughout the last three decades has almost certainly fueled the obesity
epidemic. The recent trend to substitute artificially-sweetened beverages
for sugar-sweetened beverages–an attempt to have our cake and eat it
too–-represents a public health experiment of unprecedented scale. Never
before have synthetic compounds that potently interact with ancient
biological pathways been added to the food supply in such large amounts.
Until long-term trials are available, traditionally consumed beverages such
as water, effervescent mineral water and coffee or tea (perhaps with just
one teaspoon of sugar) may be our safest choice.

No comments:

Post a Comment