Fruit or Fructose?
The Great Carbohydrate Controversy
Fruit and fructose also find themselves in a unique and (maybe) favorable position. Despite being a simple carbohydrate in chemical structure, fructose does not behave the way other sugars do in the body.
Fruit consistently ranks quite low on the Glycemic Index. They don’t cause dramatic surges in blood sugar as other forms of simple sugar such as sucrose and glucose. This also means they will not cause the corresponding spike in insulin as these other sugars do…
Therefore, you will not experience the energy crash nor the metabolic shift towards the unwanted production and storage of body fat that hormonal surges are known to produce.
This all sounds like great news since fructose has received a stamp of approval from the majority of Pop Diets over the last 20 years or so. Whether it’s South Beach, The Zone or The Paleo Diet, fructose in the form of fruit is seen as earning its place on the menu. Fructose-based sweeteners – the best known being agave nectar – are also met with approval.
So far, so good.
There is, however, just a little more to the story.
Taking the facts further requires going into a bit more detail – running down to the molecular level. This is because, as noted above, it is technically a sugar, but sure doesn’t act like one…
Once ingested, the pathway of fructose in the body is different not only from all other sugars, but also from other carbohydrates in general. While most consumed carbohydrates are converted to glycogen and shuttled to your muscles for fuel as a first step, fructose is instead sent on a path directly to your liver.
This means that for anyone who is regularly exercising – and particularly when that exercise includes resistance training – fructose and fructose-based foods are not the best choice for a carbohydrate fuel source. In fact, once digested and metabolized, less than 20% of ingested fructose actually makes it to your muscles.
While not exactly a Deal-Breaker, we could consider this Strike One.
Bringing things back to the Carbohydrate Controversy. While the remaining 80% of the fructose you eat could theoretically remain in your liver, the reality is your liver’s storage capacity for glycogen tops out in the 100-120 gram range. Unlike your muscles, your liver is rarely significantly depleted of its glycogen.
So, if there’s no room in your liver, what happens to that extra fructose in your system?
It turns out that the particular metabolic pathway of fructose is something of a mixed blessing. When your liver is at capacity, and as a result of its unique molecular structure, fructose can be easily converted from a simple carbohydrate into a long-chain triglyceride – in other words, into fat.
Keep It Real.
For your overall health and fitness, it’s a good idea to limit or omit any concentrated sources of fructose in your diet. These are natural sugars converted into a categorically unnatural form.
On the other hand, whole fruit is whole food; enjoy it.
As we discussed in the beginning, the benefits of fruit are far too numerous to ignore. When it comes to satisfying a Sweet Tooth, rounding out your breakfast or lunch and contributing to your overall health, there’s just no substitute – so don’t go looking for one at the Smoothie Shop!