Fructose from fruits is healthy – but isolated fructose is not.
Due to studies on obesity and health impacts of isolated fructose in high-fructose syrups – and constant media attention and incomplete information – most of us now associate fructose with all kinds of diseases.
Lately, it turns out that fructose from natural sources – fruits – is highly beneficial for health: newer studies have shown that fructose can actually be key to unlocking several metabolic pathways important for basic cell development and functioning.
From increased energy production to possibly even help in degenerative health conditions: we need to stop seeing sugars as an enemy, but realize that carbs are energetic nutrition! Without sugar there is no life – as with all molecules and foods, we just need to get the right amount and type, which is natural foods that we have evolved to eat.
Fructose in fruits has a different health effect than man-made isolated fructose products! For example, fructose from fructose syrup disrupt the intestinal microbiome, while fructose in fruit (inulin and other fructans) feeds our good bacteria!
The consensus in nutrition science is that whole fruits are health-promoting, which comes at no surprise to the natural health community and most of humanity.
The evolutionary perspective is in line with this consensus and is also nothing short in surprise when explaining why fruits are so healthy for us:
Humans are anatomically and physiologically specialized in fruit-eating and thus fruits are the foods we have evolved with and adapted to eat!
Like most primates, including chimpanzees, humans are biological frugivores!
And if you heard that, wild fruits are different from modern cultivated fruits: yes they are, but probably not in the way you think: wild tropical fruits – the food source of wild primates – contain even more fructose than cultivated fruits, which contain more sucrose:
“Humans clearly come from an evolutionary past in which hexose (fructose) – rather than sucrose-dominated fruits were consumed, and human digestive physiology should, therefore, be best adapted to a carbohydrate substrate similar to that of wild fruits. But, in addition, wild fruits differ in other respects from their cultivated counterparts. These include a high content of roughage – woody seeds, fibrous strands – as well as higher average protein levels, higher levels of many micronutrients … and , at times, considerable pectin.”
Kathrine Milton; 1999
Read here more on why fruits are a superior source of carbs than grains.
What is fructose, and how does it work in our cells?
Fructose is a simple sugar found naturally in fruits, but also vegetables, and honey. The breaking down (metabolization) of fructose molecules generates energy. Besides being an important source of energy for cells, providing up to 48 molecules of ATP (the universal energy carriers in cells) per molecule, fructose is used in the production of amino acids, nucleic acids, and fatty acids. This makes fructose an important part of cellular metabolic processes.
What is the process of transport of fructose into cells?
Fructose is taken up by cells via the GLUT5 transporter. Unlike glucose transporters (see image below) the fructose transporter GLUT5 is insulin-independent. It is expressed in many types of tissues (see below), which means that fructose can enter various cell types of the body and readily deliver the energy for our metabolism without the production of insulin! This is why fructose is interesting for people with insulin issues.
Once inside the cell, fructose can be used by the cell via fructolysis (similarly to glycolysis) to produce energy, which ultimately powers all energy-dependent processes within the body!
Fructose can also be transformed and stored in the form of glycogen for later use, if there is not an immediate need for the energy.
In what type of cells fructose is used?
Fructose is taken up by the small intestine and primarily metabolized by the liver, but it can also be used by other tissues, like kidneys, the brain, skeletal muscles, and fat cells. In particular, fructose is efficiently absorbed and utilized by:
- muscle cells
- adipose tissue cells (fat cells)
- hepatocytes (liver cells)
- renal proximal tubular epithelial cells (kidney)
- intestinal enterocytes
- pancreatic beta cells
- several types of brain cells
Fructose uptake (the expression of GLUT5) depends on species, age and health. And, as frugivorous species, humans absorb and use fructose by many cell types – a characteristic that has likely evolved as an adaptation to the consumption of fructose-rich food (fruits!) as the main part of the natural diet. As a result, fructose from fruits has become an important energy source for many tissues of humans. Fructose can be used to produce ATP (adenosine triphosphate), which is the main form of energy used by cells in the body. Thus, fructose is a vital source of energy for many cells.
How does fructose help the body to function?
Fructose has been found to play an important role in the regulation of blood sugar levels, energy metabolism and lipid metabolism. Therefore, it is essential that cells are able to absorb and use fructose efficiently for proper functioning of the body.
Here are some of the benefits from fructose in fruits:
- Easily available energy source without insulin spikes: Fructose serves to provide energy for the body as it is broken down into glucose which can be used by cells for metabolic processes. As easy energy, fructose enables all energy-requiring cell activities.
- Less tasking to the pancreas: Because fructose does not trigger insulin production, the pancreas gets a break!
- Intestinal nutrient absorption: Fructose is necessary for the effective absorption of certain vitamins and minerals in the intestine.
- Microbiome health: Fructose (oligo-fructose “fructan” from fruit) promotes healthy digestion by providing essential dietary fibers and food for the microbiome that help to break down food and absorb nutrients.
- Avoids insulin and blood sugar spikes: Fructose is less likely to cause less oxidative damage in cells compared to other sugars, such as glucose, because of insulin independency.
- Cellular communication: Fructose is involved in cell signaling.
- Helps regenerate and protect cells: Fructose provides protection against cell damage caused by environmental stressors such as ultraviolet radiation and toxic chemicals.
How is fructose from fruits helpful for people with insulin problems?
Fructose from fruit is an excellent energy source for people with insulin problems. Unlike other simple sugars, it does not raise blood glucose levels and can be digested without the need for insulin.
This makes it a great option for those who require careful regulation of their blood sugar levels due to diabetes or other health concerns. Fruits also provide essential vitamins and minerals, making it a valuable source of nutrition. Additionally, the consumption of fruit can reduce hunger and cravings for sweet foods.
All these factors make fructose from fruits (not isolated fructose!) an ideal energy source for people with insulin problems.
Are there any risks associated with high levels of fructose intake?
There are risks associated with high levels of fructose intake, but only if fructose is isolated: a high intake of added sugars, including isolated fructose, has been linked to numerous health issues such as weight gain, type 2 diabetes, metabolic syndrome, and cardiovascular disease. Long-term consumption of high amounts of fructose can also lead to fatty liver disease due to its effect on increasing sugar levels in the body.
However, when eating a high-fruit diet, too much fructose from natural sources is not a thing! This is confirmed by many studies on the effects of fruits on health, even in people with insulin problems. If you still have doubts, ask a chimpanzee…
Learn more about the frugivore diet and the human species-appropriate diet:
Go to How to do the Frugivore Diet
References
- Fructan (2023) Wikipedia. Wikimedia Foundation. Available at: https://en.wikipedia.org/wiki/Fructan (Accessed: April 4, 2023). (link)
- Milton, K. (1999) “Nutritional characteristics of wild primate foods: Do the diets of our closest living relatives have lessons for us?,” Nutrition, 15(6), pp. 488–498. Available at: https://doi.org/10.1016/s0899-9007(99)00078-7. (link)
- Biochemistry, fructose metabolism – statpearls – NCBI bookshelf (no date). Available at: https://www.ncbi.nlm.nih.gov/books/NBK576428/ (Accessed: April 4, 2023). (link)
- Hundal, H.S. et al. (1998) “GLUT5 expression and fructose transport in human skeletal muscle,” Advances in Experimental Medicine and Biology, pp. 35–45. Available at: https://doi.org/10.1007/978-1-4899-1928-1_4. (link)
- Taylor, S.R. et al. (2021) “Dietary fructose improves intestinal cell survival and nutrient absorption,” Nature, 597(7875), pp. 263–267. Available at: https://doi.org/10.1038/s41586-021-03827-2. (link)
- Briden, L. (2022) High-dose fructose can cause or worsen insulin resistance (but fruit is okay), Lara Briden – The Period Revolutionary. Available at: https://www.larabriden.com/quit-sugar-and-what-i-mean-by-sugar/ (Accessed: April 4, 2023). (link)
- Li, M. et al. (2014) “Fruit and vegetable intake and risk of type 2 diabetes mellitus: Meta-analysis of prospective cohort studies,” BMJ Open, 4(11). Available at: https://doi.org/10.1136/bmjopen-2014-005497. (link)
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