Millions of years ago, our ancestors used sugar for energy production and energy storage for survival. Because of various type of sugars, they were able to survive through starvation, ice age, hibernation and so forth. We are results of their evolution, however, so many things have changed and some of the evolutionary changes may not be necessary. How our body metabolize or utilize sugar is one of them.
Thanks to the medical, nutrition and fitness industry, we begin to understand and recognize what sugar can do to our health. Just like fat, salt, protein, and other nutrients not all sugars are created equal, and they do serve different purposes.
Different Types of Sugar
There are different types of sugar. One is called glucose. Glucose is mainly found blood and known as blood sugar. It is a primary sugar that our body use to produce energy, adenosine triphosphate (ATP). Glucose can be stored as glycogen in muscle, liver, kidney for immediate use. When glucose or blood sugar is too high, we’ll have diabetes, and when it is too low, we’ll have hypoglycemia.
Another type of sugar is called fructose. It is a natural sugar found in fruits and honey. Fructose is involved in energy storage rather than energy production. The body store fructose in form of glycogen and fat. Compared with glucose, fructose is sweeter than glucose.
Table sugar or sucrose is combination of glucose and fructose in 1 to 1 ratio which can be found in sugar cane, maple syrup and beets.
Popular sweetener called high fructose corn syrup is glucose and fructose in ratio of 45/55 which commonly found in soft drinks.
Purpose of Fructose
Fructose as mentioned is involved in storage of energy rather than production of it. Many animals consume fructose through fruits to store fat to prepare their body for possible starvation or hibernation. Million years ago, our ancestors consumed fruits to obtain fructose to survive ice age and starvation. We currently can consume fruits without storing fat since we tend to eat tart fruits, which has less sugar content, and consume less portion compared to animals. Fruits juice, however, has higher concentration of sugar and fructose which can increase fat storage.
Fructose Lowers Metabolism
When we consume any form of macronutrients, carbohydrate, fat, and protein, our body typically break them down to create energy or ATP. ATP is currency of our energy. Because of ATP, we can talk, walk, run, think, breath, and so on. Even when metabolizing these macronutrients, including glucose and fructose, requires some ATP to make more of it.
When glucose is metabolized, some ATP is spent to start the metabolic process, but our body has feedback mechanism to stop the process, by enzyme called phosphofructokinase, to avoid significant ATP depletion.
When fructose is metabolized it is different. When there is accumulation of fructose, ATP level decreases by 40-50%, which means body is trying to preserve energy, mostly regulated by enzyme called fructokinase. This also affect our metabolism, resting energy expenditure, pushes macronutrients consumes into fat and glycogen. It also seems to trigger our ghrelin, hunger hormone, and thirst.
Normally, because of homeostasis, our body weight is regulated. May see minor fluctuation but usually stays in the same body weight range. Even when you force yourself to eat or starve yourself, our weight will go back once we go back to how we normally eat.
However, especially animals, when fat gain is required, it seems to happen through mechanism that involves fructose. So when you look at animals hibernating, they will start eating a lot of fruits, which contains a lots of fructose, drops their metabolism so that they can store energy, or fat and glycogen, to survive through hibernation.
For practical sense, when we consume fructose..
1. ATP depletion
2. Decrease Metabolic Rate
3. Generate Body Fat
4. Condition our body to insulin resistance, fatty liver, hypertension
5. Which leads to obesity
This process is survival mechanism that has been embedded in our system through evolution.
Eat It Not Drink It
When comparing ways of sugars been consume, drinking sugar is worse choice compared to eating. This is because when drinking sugar, excessive amount of fructose can be consumed within short period of time. Which also means that high fructose concentration can enter the body and trigger metabolic process for fructose which illustrated above.
Compared with eating versus drinking fructose, even with equal amount, speed and concentration of fructose consumption is different. Therefore, if you were to consume fruits, it is ideal to eat rather than drinking it.
Challenge of Limiting Fructose Consumption
If we could reduce fructose intake, it will have tremendous health benefit. However, challenges that we have is our body can create fructose and sugar and high fructose corn syrup can pretty much in majority of food sources, especially processed foods.
One of the ways that the body makes fructose is when consuming high salty diet. Although salt is essential to our health, high salt diet has link to high blood pressure, obesity, and diabetes. Interestingly though, it is not so much about amount of salt we are consuming, but the concentration of salt that trigger the body to produce more fructose in our body from glucose.
Another way for our body to make fructose is when we get dehydrated. This connects with consuming high salt diet, especially with things like chips and fries. When we consume too much salt, we get thirsty. This is mainly due to salt and water imbalance which seems to be the trigger for our body to start creating fructose. Therefore, it is suggested to drink water prior to consuming salty food. It is also important to stay hydrated throughout the day to keep the fructose level low as much as possible for following reason.
Although we’d like to limit our fructose intake, you can find sugar and high fructose corn syrup in everything, especially in processed food and soft drinks. Dried fruits, though it may seems healthy, they are highly concentrated with fructose.
In 1800s, it was popular to add sugar to their beverages much more than today. This high sugar intake through beverages lead to increased the uric acid level which lead to gout and high blood pressure.
Are Fruits Safe?
We know that the fructose, unlike glucose, has a different metabolic pathway and directly goes to store energy as glycogen and fat. We also understand that this can lead to insulin resistance, fatty liver, hypertension and obesity. Since fructose is a fruit sugar, the question often asked is are fruits safe? Sweeter fruits tend to have more fructose than those fruits that are tart.
Fruits with higher fructose are banana, apple, watermelon, mango, etc. Fruits that are low in fructose are lemon/lime, kiwi, blueberry, raspberry, strawberry, cantaloupe, honeydew, etc.
It is also important to understand that fructose can be used in certain way. If you are going on a long hike, participating in competitive sports, or training at the gym, fructose can be used as reserve and restoring energy. Just like sports drink, if you are physically active, it can have benefit in hydration and replenish glycogen and minerals. However, if you are not physically active, sports drink may not be a good option to be drinking. This is same with consuming fruits.
When you are eating fruits, even with those with low fructose, keep the portion in mind. Too many fruits in one sitting is not recommended. 1 handful will be plenty and rather than drinking it as smoothie or juice, eat it to avoid spike in fructose concentration.
There is nothing wrong with eating fruits, since it does have so many good nutrients. However, when consumed in abundance like fruits bowl or juicing, you can consume more fructose which can outweigh those good nutrients, which may cause health issues.
Kota Shimada
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