Fruits (fructose) - the ‘sweet’ truth you should know
The fitness industry is often split into a conundrum. One, often propagating ‘broscience’ vs another, that is backed by science. Fruits have been one such hot topic, where both these sides have locked horns. What makes this such a debatable topic and what is actually true?! Let’s find out!
‘Fruits are bad for your health, they make you fat. Period.’
Well, this statement is not just a random idea that popped inside one’s head and they spoke it out. There was some thinking that went behind it. The major thought that goes into this is that fructose (fruit) sugar is metabolized and stored in your liver glycogen. If you have eaten some other carb meal any other time of the day, there are chances that your liver glycogen is full. Now that it cannot store energy, the excess is going to be converted to fat. Thus, fruit makes you fat. It makes sense when put across this way, doesn’t it? Although the above assumption or explanation might sound promising, current scientific evidence suggests otherwise. First things first, the studies that have often linked fructose with ‘bad health’ are studies conducted on rats. Most of the times, this data does not replicate on humans. So to truly understand the health implications, we have to look at studies performed on humans.
Following are findings of studies done on fructose metabolism in humans :
- A large proportion of fructose (anywhere between 26 to 80%) is oxidized by the liver within 3 - 6 hours. A fair amount of fructose (22 to 56%) is converted to glucose by hexokinase and phosphoglucose isomerase within 6 hours of consumption .
- Some fructose is actually converted to VLDL triglycerides. A study showed that lipogenic potential of fructose seems to be small since only 0.05% and 0.15% of fructose were converted to de novo fatty acids and TG-glycerol at 4 hours, respectively .
- Substitution of complex carbs like whole wheat bread with sugar without changing the caloric intake had no effect on body composition .
- A 6-month study consisting of almost 400 participants with different sources of carbohydrates showed no significant change in body composition on blood lipids .
The following figure represents what fructose metabolism looks like in humans :
But wait, you might feel that I am favouring studies that support my claim. Let’s not do that. There was a study that showed detrimental effects of a high fructose diet on health. The outcomes being decreased insulin sensitivity and increased fat content in liver .
The fruit naysayers might be beaming with happiness.
The problem, with such studies, is the dosage. The subjects that faced these health issues were being fed fructose at 3 grams per kg of body weight. In the very same study, subjects being fed fructose at 1.5 grams per kg of body weight did not show any signs of declining health.
“Enough science! I do not care about all this, what do I do?!”
For those not interested in this scientific mumbo jumbo, here are a few practical recommendations :
- Fruits are not bad, do not be scared of them.
- Fruits do not make you fat, it is your overall diet that does, calories are the king when it comes to losing weight (Nutrition eBook here).
- Fruits are rich in micronutrients. Have 1 - 2 servings of fruits in a day, if your diet permits.
- They are a better snack option than your regular choco chip cookies.
- Obscenely high amounts of fructose (>150 grams a day) may be detrimental in the long run, moderation is the key.
Article Contributed by - Pratik (CoFounder - GetSetGo Fitness)
1. http://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075- 9-89