Are fruits and fruit juices a good source of energy? Or are they secretly contributing to your fatigue levels?
Fruits are healthy, right?
From a big picture point of view, yes, fruits are generally healthy. However, upon closer investigation, nature’s healthy sweets could secretly be making you tired.
Whether a fruit conveys a health benefit or contributes to a health issue strongly depends on your individual circumstances. Have you heard the adage: “One man’s food is another man’s poison.”? This holds true for all food. Especially fruit.
What is fruit made of?
I’m going to skip the biology behind fruit and focus on the micronutrients and macronutrients found inside. The term macronutrient describes the chemical substances that provide calories for energy. You know macronutrients as carbohydrates, proteins, and/or fats.
Micronutrients include the many essential vitamins and minerals required in smaller amounts. Nearly all foods, (with the exception of items such as candy that provide only calories with no nutrients), provide some amount of both macro and micronutrients. Fruits provide both macronutrients (in the form of carbohydrates and a little protein) and micronutrients (like b vitamins, and vitamin c).
Why you need fiber to overcome fatigue
Fruits contain natural sugars and fibers classified as carbohydrates that your body uses for energy. While both sugars and fibers are carbohydrates, they behave very differently within your body. Fiber is a type of carbohydrate that your body cannot digest. You cannot digest fiber because you lack the digestive enzymes to break it down. Cows have four stomachs to ensure they can properly break down the fiber found in grass and extract all the nutrients from it.
There are two different types of dietary fiber:
- Soluble fiber
- Soluble fiber is soluble in water
- Insoluble fiber
- Insoluble fiber is not soluble in water
Soluble fiber attracts water to it during digestion. It becomes a gel-like substance in your intestines. Insoluble fiber passes through your digestive tract unchanged. Insoluble fiber is likely what comes to mind when you think of fiber. It is found in grains, fruits, vegetables, and legumes. Bran muffins are a classic example of an insoluble fiber.
Insoluble fiber adds bulk to your stool and helps to alleviate constipation. But soluble fiber may actually be more important. Soluble fiber includes oligosaccharides which are prebiotics. Prebiotics are food for the bacteria in your digestive tract. It is thought that prebiotics may be even more important than probiotics for intestinal health. (1)
Examples of soluble fibers include chicory root, Jerusalem artichokes, onions, garlic, leeks, and green bananas – foods most people in the developed world do not each much of.
Fruits consist mainly of insoluble fibers. When you blend or juice a fruit, you break up these fiber bonds. With this decrease in fiber, fruit juices or smoothies have a more dramatic, and negative, effect on your blood sugar.
Fruits are mainly carbohydrates. Sugar is a carbohydrate. And sugar is the main source of carbohydrates found in fruits.
But the sugars found in fruit are better than the sugars found in refined food products, right?
Not necessarily. The sugar in fruit has less of an effect on your blood sugar only when it is accompanied by fiber.
Fiber does not raise your blood sugar. When you eat a fruit, you are taking in carbohydrates in the form of sugar and fiber. Fiber helps to balance your blood sugar. (2) But if you juice your fruit or blend it up in a smoothie, you’re destroying the fiber. In this case, the sugar of the fruit exerts an effect on your blood sugar the same way a sugary soda drink will.
Notice the carbohydrate total for the orange is 11 grams. The fiber content is 2.3 grams. Therefore, the net carbohydrates for the orange is 8.7 grams (11g – 2.3g = 8.7g).
The fiber contained within the orange helps to keep your blood sugar from spiking. When you remove the fiber (like in orange juice), you’re making a sugary drink that’s not too far off from a can of cola.
Compare this with one glass of orange juice. (source) One cup of raw, freshly squeezed orange juice has 26 grams of sugar in it and only 0.5 grams of fiber. Therefore, the net carbohydrates in a glass of orange juice are 25.5 grams (26g – 0.5g = 25.5g).
To better put this in perspective, a can of your favorite pop will have around thirty grams of sugar in it (with no fiber content). A can of pop has less than five grams more sugar than a glass of “healthy” orange juice.
I’ve written a great deal about how high levels of carbohydrate intake can cause fatigue. By altering your blood sugar levels, that ‘healthy’ morning smoothie or glass of juice could quietly be causing your fatigue.
If you’re working towards overcoming fatigue, I recommend you hold off on juicing, juice cleanses, and daily smoothie consumption. The high sugar content found in fruit juices and smoothies will likely only compound your energy issues. Opt for eating whole fruits – but only in moderation!
This is because blood sugar aside, there are other harmful pathways that fruits could be causing your fatigue!
Glucose, fructose, and fatigue
I’ve gone on and on about how sugar (glucose) affects your energy levels. But there’s another form of sugar that may be of even more detriment to your energy levels. This form of sugar is known as fructose. You’ve probably seen it on ingredient lists as “high fructose corn syrup“.
High fructose corn syrup is an inexpensive way to sweeten food. It’s often used to make bland, unappetizing foods palatable. Cover anything in enough sugar and it’s bound to taste good.
Fructose behaves in a very different manner than glucose. Fructose will not increase your blood sugar as glucose does. (3) Check your blood sugar after gorging on high-fructose corn syrup and you’ll find relatively stable readings. But before you jump on the fructose bandwagon, know that it could very well be an insidious cause of your fatigue.
How fructose causes fatigue
Unless you’re on a ketogenic diet, your body uses glucose for energy. No glucose, no energy. Your body cannot run on fructose for energy. Nor can your body convert fructose into glucose (energy).
When you consume fructose, it is first absorbed into circulation in your small intestine. From there, it heads straight to your liver. Fructose can only be metabolized within the liver whereas glucose can be metabolized nearly anywhere in the body. (4)
What does your liver do with fructose?
Since it cannot use fructose as energy, the only option is to put it into storage. And the storage of fructose is done via body fat. Fatty liver disease can develop when you consume too much fructose. With excess fructose, your liver is forced to store it as fat. This fat storage pattern is how fructose causes fatigue.
Fat, fatigue, and fructose
High-fructose corn syrup now represents nearly 50% of the sweeteners used in the United States. (5, 6) And from reading the above, you know now that fructose contributes to the addition of fat on your body. Fructose has even been linked as a potential contributor to the obesity epidemic in developed nations. (7)
When your body has excess body fat, you’re at increased risk for developing diabetes. (8)
Your adipose (fat) cells release hormones and inflammatory markers. (9) The more weight you gain, the stronger the effect these hormones and inflammatory markers have on your health. In obese individuals, the effect can be severe.
When you’re overweight, your body creates substances known as non-esterified fatty acids (NEFAs). NEFAs cause insulin resistance AKA: diabetes. When you lower your NEFAs you lower your risk for diabetes.
When insulin levels get unbalanced, cortisol levels almost always become unbalanced. Your body typically has an increased demand for cortisol when it struggles to balance its blood sugar (like in diabetes). Over time, this high demand for cortisol results in hypocortisolism (also known as adrenal fatigue).
This multi-step process is how fructose causes fatigue. You won’t experience fatigue immediately after consuming fructose. The fatigue developed by fructose occurs over a long period of time.
My recommendation: if you’re working to overcome fatigue, avoid all sources of refined fructose and limit your consumption of fructose-containing fruits.
Foods with fructose
Fructose is a naturally occurring sweetener in fruits. The following fruits are known to have high levels of fructose (eat in moderation):
The following vegetables contain high levels of fructose (eat in moderation):
- Sugar snap peas
The following refined foods contain high levels of fructose (avoid completely):
- Sweetened/ flavored yogurt
- Salad dressings
- Granola bars
- Breakfast cereals
- Sports drinks
To overcome fatigue, achieving a healthy weight and balanced blood sugar are absolutely essential. Seemingly healthy fruits, juice cleanses, and smoothies can seem like quick wins to improve your energy. In reality, they often do more harm than good.
Be sure to steer clear of all refined foods high in fructose (and glucose for that matter). As a general rule of thumb, do your best to limit or avoid tropical fruits. These fruits often contain the highest glucose and fructose content. Instead, opt for berries.
Blueberries, blackberries, strawberries, raspberries, and huckleberries contain lower amounts of glucose/fructose. They’ll help keep your blood sugar stable and not contribute to body fat.
If you’re going to take away one thing from this post, I want it to be that in the context of overcoming fatigue, so-called “healthy” juices, juice cleanses, and/or smoothies may actually be making you tired. Do your best to keep their consumption minimized.
Learn more than your doctor about which foods cause fatigue!
Also published on Medium.