As of late, Fructose has been popping up in the media left and right. While many of the articles are fairly accurate on the assertions they make about fructose, others are quite misleading. I believe there needs to be a bit of clarification on the subject and an exposé of what some of the articles might not be telling you.
What is Fructose?
Fructose is a monosaccharide hexose sugar found mostly in fruits, some vegetables and honey. It is essentially fruit's form of sugar. Many times it is found bonded to glucose to form the disaccharide sucrose (AKA table sugar). As opposed to other sugars such as sucrose, which requires further processing in the intestinal cells, fructose is absorbed directly into the bloodstream. It is predominately processed by the liver and then distributed to the body's cells for energy.
Fructose vs High Fructose Corn Syrup
While fructose itself is made up of one type of sugar, high fructose corn syrup (HFCS) is a varying ratio of fructose and glucose. HFCS is produced by taking regular corn syrup and enzymatically changing it to convert the glucose into fructose - primarily since fructose is sweeter than glucose - about 1 1/2 times sweeter.⁽¹⁾ The reason HFCS is used so widely is due to its cheap cost compared to other types of sugars. While HFCS is not inherently 'bad,' it makes it easy to consume a large amount of calories in a relatively small amount of food. Not to mention that HFCS lacks all of the nutrients that fructose containing foods traditionally provide (think bright colored fruits).
Common Fructose Myths
There are many myths surrounding fructose, here I will highlight a few of the more prominent ones:
Myth: Eating fructose will cause me to gain fat
The Science: First off, eating too much of almost anything can lead to weight gain at a certain point. Often times fructose gets confused with the previously mentioned HFCS. While numerous studies ⁽²⁾ have shown that fructose can be converted preferentially into triglycerides (fats), in the liver, which leads to elevated blood triglyceride (fat) levels, this is only in a small segment of the population. The majority of the population handles fructose just fine and can eat a varied diet containing plenty of fruits and maintain a healthy weight. Where the weight gain starts to come in, is in the populations that are consuming large amounts (2-3 per day) of soft drinks and baked goods containing HFCS.
Myth: Fructose won't fill me up, making me just want to eat more
The Science: This myth is based upon the notion that the body does not respond to fructose the same way it responds to other sugars. Some studies have shown that fructose does not stimulate the release of the hormone leptin (AKA the 'satiety hormone') The data ⁽³⁾ shows that fructose does stimulate release of leptin, just not to the extent of other sugars. Another factor that comes into play is the volume/fiber that fructose-contain foods (mostly fruits) provide. After eating a whole apple, you are likely to feel slightly full vs drinking a soda, where you are likely to not feel full.
Myth: Eating fruit at night will make me gain weight
The Science: The common logic for this myth is that eating fruit at night or before bed will spike your blood sugar at a time when you are least active, causing weight gain. The most important principle here is caloric balance, which is calories in versus calories out. If you have consumed predominately whole, unprocessed foods throughout a given day and implemented portion control, eating a piece or two of fruit at night would likely benefit you as opposed to make you gain weight. On the other hand if you had fast food for breakfast and lunch, then a fatty cut of steak for dinner, that piece of fruit might add to the caloric surplus you are in for the day, leading to weight gain. Bottom line, its not the actual food item that is making you gain or lose weight, its the overall amount of calories you are taking in.
Recommendations for Fructose Consumption
While there is really no definite amount of fructose that you should or should not eat per day, moderation is always key. You would not want to eat 6 bananas or 5 apples in one day, unless that is going to help you reach your goals. The general recommendation is at least 2 servings of fruit per day with no established upper limit. As far as HFCS goes, you want to consume as little as possible on a daily basis. Some individuals can tolerate more than others. This is a matter of personal experimentation. You can yield far more nutrients when eating fruit or vegetables than when drinking a soda, but this doesn't mean you should never drink soda. It just means that you should limit how much you consume.
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