Sweet, simple sugars get the worst reputation of all the carbs – which is counterintuitive given that we have evolved to love the sweet taste and crave sweet foods! Nature has shaped traits – like “loving sweet” – to our advantage for survival and reproduction. In this case, sweetness indicates energy-rich foods to fruit-eating animals. A bitter and off-putting taste, on the other hand, signals harmful substances. How can we accept the claim that “sugar is toxic” in light of this most basic biological fact? It is time to elaborate on the role of sugars in biology and living organisms so we can abandon the damaging “toxic sugar” myth or the “war on sugar” with good reason!
Here are some of the most convincing reasons why sugar should not be called toxic – at all:
1. Sugar is a nutrient – not a toxin!
The natural and vital role of carbohydrates (including glucose and fructose) from foods is to provide fuel for our body: they are energetic macronutrients. All nutrients are, by definition, needed for health and are thus non-toxic substances (always under consideration of the rule that the “dose makes the poison”). It is basic biological knowledge that backs-up that carbs are essential. We literally ignore every “basic of biochemistry and biology” book if we say that sugars should be avoided!
Saying that “sugar is toxic” is like saying that fats are toxic or proteins are toxic. Consuming a large amount of isolated fat will get you into health troubles faster than sugar, and isolated amino acids cannot be consumed in large amounts (see example here). However, they all play a vital role in biological systems and are healthy when consumed via natural foods!
The “sugar is toxic myth” might talk about isolated sugar… and this must be communicated clearly to avoid the misconception of “sweet is generally bad”.
To understand better that sugar is a nutrient, that we need in large amounts and is extremely safe even in high amounts, consider this: isolated sweet sugar can be ingested in large amounts without acute toxicity (in contrast to isolated amino acids). Of course, this is not healthy in the long run! But, children can go crazy on candy and cake at birthday parties, without experiencing toxicity. Interestingly, candy is some sort of “cheap and unhealthy” substitute for fruits, which we naturally crave, but dis not always have available in colder climates.
2. Sugar provides energy for our metabolism
Sugar is a macronutrient that occurs in large amounts in foods and provides energy. Only when we isolate sugars can they be consumed in excess and add to the building up of fat tissue and get us health problems. However, naturally occurring simple sugars are what primates (including humans) use as preferred fuel (read more here). This is why sweetness is so appealing to us, and why we do have evolved taste receptors for sweet in the first place! Liking sweet sugars serves a function, as we are attracted to the molecules that carry and deliver energy to our cells: Glucose (and fructose) is broken down to the energetic molecule ATP and power all cellular processes that require energy (read more here on how cells get energy from food).
Illustration: In the cell the small energetically loaded molecule “ATP” is produced from glucose, in order to carry that energy to energy-requiring biochemical reactions. Humans are adapted to primarily run on glucose.
3. Frugivory: humans are adapted to fruits and simple sugars
Humans love sweetness for a good reason: we are high fruit-eaters – also called frugivores – similar to chimpanzees, which have around 70% of tropical ripe fruits in their diet! Children instinctively love sweets, because sweet fruits are the species-specific food group of humans. Besides the attractions, we do have many adaptations to fruit-eating (see here).
Sweet fruits attract fruit-eating animals (frugivores), including humans! Simple sugars are their primary source of energy! We have evolved to love sweet taste and are adapted to eat large amounts of sweet fruits – and thus to eat simple, sweet sugars (see here).
Humans have developed sweet taste receptors to identify and like foods rich in simple-sugars (energy-rich), mainly fruits, to find their foods and survive!
4. The body needs to produces glucose itself, if we don’t eat it
If we do not take in sufficient glucose, the body itself starts to synthesize glucose from fatty acids or proteins. This is called “gluconeogenesis” and happens when the ketogenic energy metabolism is activated – under the production of the stress hormone cortisol! This newly produced glucose is also used for the brain.
In other words, not having enough sugar from food, is a stressful situation to the body. Which is perfectly fine for a short while, i.e. while foraging food in nature, but not long-term.
5. No sugar, no life!
There would be no animal life without sugar! Sugar is thus the basis of life: it is literally sunshine energy stored chemically.
“Sugar” refers to a chemical group of energetic nutrients in natural foods – especially in plants. Plants produce glucose and fructose as energy carriers and energy-storing unit: green plant cells (leaves) collect electromagnetic energy directly from sunlight and – thanks to a complex transformation called photosynthesis – converts it into energy that living cells can use. The glucose and fructose is then stored as starches or transported to the fruits, to attract and reward fruit-dispersing animals with sweetness. Thus, sugars provide the energy for all our metabolic processes!
6. Isolated fructose is not like fructose from fruits
Fructose gets a bad reputation because the isolated fructose in high-fructose-corn-syrup has shown to be unhealthy. But this is not only the case for fructose: generally, too much of any isolated chemistry is damaging! Even isolated H2O (water) molecules can be damaging in excess!
However, fructose within fruits is beneficial for cellular health, which is why there are no studies that show fruits are not beneficial for health! To the contrary, academia is rediscovering the ancient knowledge of the rejuvenating and health-promoting effect of fruits.
Read this in-depth article on the benefits of fructose in fruits here.
7. We can uptake and metabolize fructose without insulin
Our body can use glucose and fructose for energy supply. Fructose occurs mainly in fruits, and it turns out it is the most accessible sugar for our cells to uptake and thus use for energy.
Humans have a biochemical pathway called fructolysis, where fructose is broken down to gain energy. Fructose is used for energy directly in many types of cells, not only liver cells – as it was previously believed and still stands strong as an outdated remnant of erroneous information!
Further, in contrast to glucose, fructose, the typical sugar type in fruits, can pass into the cells without insulin! Fructose enters through a specific transporter called GLU5, which does not require insulin to “open up” and transports fructose exclusively.
This means, we take up sugar from fruit even better than glucose. And, people with insulin issues, can utilize fructose from fruits without insulin. However, fruits contain both, fructose and glucose.
Our cells can take up fructose without the help of insulin: Insulin is a key that is only needed to open the cells to glucose.
8. Do you think starches are toxic, too?
Complex carbs, like starches, are the same as simple carbs – just bonded and not sweet!
Complex carbs are the plant’s storage form of simple sugars, for example, in roots or unripe fruits. Starches are nothing else than simple sugars bound to each other. While simple sugars, like glucose and fructose, taste sweet to our taste buds, complex carbs, like starches, do not trigger our sweet receptors. Therefore, when we eat complex carbs, we miss out on the sweet taste but still get the same amount of energy!
This means that a handful of rice (complex sugar) contains nearly the same amount of sugar (and calories) as a handful of concentrated sugar (i.e. coconut sugar). Rice is just not sweet, which is why we do not realize the amount of sugars we eat, as complex carbs are split into simple carbs during digestion. And… who would say carbs in rice are “toxic”?
Learn more about the natural human high-fruit diet:
Go to How to do the Frugivore Diet
- Nutrient. Education (available at https://education.nationalgeographic.org/resource/nutrient/). (link)
- Food supplements – high intake of isolated branched-chain amino acids … (available at https://mobil.bfr.bund.de/cm/349/food-supplements-high-intake-of-isolated-branched-chain-amino-acids-can-lead-to-health-impairments.pdf). (link)
- Racusen, L. C., Whelton A., Solez K., Effects of lysine and other amino acids on kidney structure and function in the rat. The American Journal of Pathology (1985) (link)
- K. Milton, Nutritional characteristics of wild primate foods: Do the diets of our closest living relatives have lessons for us? Nutrition. 15, 488–498 (1999), doi:10.1016/s0899-9007(99)00078-7. (link)
- How cells obtain energy from food – molecular biology of the cell … (available at https://www.ncbi.nlm.nih.gov/books/NBK26882/). (link)
- N. A. Tamrin et al., New insights on the evolution of the sweet taste receptor of primates adapted to harsh environments. Animals. 10, 2359 (2020). (link)
- L. R. Engelking, Gluconeogenesis. Textbook of Veterinary Physiological Chemistry, 225–230 (2015), doi:10.1016/b978-0-12-391909-0.50037-2. (link)
- S. Khani, J. A. Tayek, Cortisol increases gluconeogenesis in humans: Its role in the metabolic syndrome. Clinical Science. 101, 739–747 (2001), doi:10.1042/cs1010739. (link)
- Photosynthesis. Education (available at https://education.nationalgeographic.org/resource/photosynthesis/). (link)
- S. J. Dholariya, J.A. Orrick, Biochemistry, Fructose Metabolism, NCBI Bookshelf (available at https://www.ncbi.nlm.nih.gov/books/NBK576428/). (link)
- V. Douard, R. P. Ferraris, Regulation of the fructose transporter GLUT5 in health and disease. American Journal of Physiology-Endocrinology and Metabolism. 295 (2008), doi:10.1152/ajpendo.90245.2008. (link)