We do need to delve into a little biochemistry to learn that not all sugars are bad sugars.
Our metabolic processes and especially our brain need glucose to function. Sometimes we even need to convert fat and proteins into glucose through a process called gluconeogenesis. We also store glucose as glycogen in our muscles which forms part of our blood sugar maintenance and how we store energy we need quickly when we work hard.
There are a host of other good sugars that form part of many antioxidants we need. These are unfamiliar sugars to most people - ribose, galactose, mannose, sambubiose, rhamnose, rutinose, etc. Good sugars are also components of anti-inflammatories and anti-carcinogens. They are highly functional. Quercetin, for example, is an important anti-inflammatory. It forms the glycosides quercitrin and rutin and both incorporate the good sugars, rhamnose and rutinose, respectively. Many other functional food components are good sugars bound with other sugars, proteins or fats.
These good sugar bound molecules even form the outer coating of cells and help them communicate with one another and with the cellular environment. This is critical for good cell hydration and our good health and wellness.
It is good to see the debate on bad sugars (sucrose and fructose) spreading into the public domain.
Although some attempts to hang on to the 'values' of fresh fruits by claiming they are OK in terms of sugar need to go.
It's not true. Bad sugars are bad sugars and our modern fruits are over-loaded with them. Mangoes can have 3% more bad sugars that the same weight of Coke or Pepsi. Pineapples, melons, berries, grapes and any sweet fruits (and vegetables) are the same and don't even think dried fruits are good for you. Dates can have up to 65% bad sugars and dried grapes, blueberries and other fruits are not far behind in their bad sugar contents. Some dried fruits are even coated in sucrose, just for its addictive qualities, I guess.
The problem with our produce is that large, juicy, super-sweet fruits sell. Too bad fibre content and the levels of phytonutrients plummets as we breed and grow for sweetness. See this article (breeding-the-nutrition-out-of-our-food) for more on this.
The food industry also 'normalizes' fruit juices in production. If say, apples and oranges can have up to 10 or 12% sugar when they are really ripe then juice made from less ripe fruits can be boosted with cane or beet sugar and still labeled as 100% natural, no added sugar. The adjective 'added' here is defined as 'more than potentially normal'.
But he real bad boy in sucrose and in fruits is fructose. Check out the details (does-fructose-make-me-look-fat-in-this) in this article.
In summary, fructose is metabolized in the liver where it can lead to numerous by-products including uric acid which lowers levels of nitric oxide which boosts blood pressure. Along with uric acid-induced salt sensitivity, the elevated BP may protect against dehydration during fasting. Fructose and its metabolic products also lead to fatty liver and elevated triglycerides in the blood - precursors of heart disease.
Uric acid (and fructose which both influence insulin and leptin resistance stimulating appetite) appear to drive the fat accumulation phase in hibernating species and the urge to wake and feed post-hibernation. In humans an elevated uric acid level precedes the development of obesity, hyperinsulinemia and diabetes. Studies therefore suggest that uric acid has a causal role in obesity and metabolic syndrome.
Additionally, fructose in fruits rises as fruits ripen and bears, for example, feast on huge volumes of over-ripe berries at the end of summer and just prior to hibernation in many parts of the world from Sweden to Canada.
As fructose rises, so vitamin C activity falls in ripening fruits and it has been shown that vitamin C neutralizes some of the effects of fructose and uric acid to induce metabolic syndrome. This means that over-ripe fruits, with their high level of fructose and low vitamin C could increase the impact of fructose to increase body fat stores.
So the bad sugar story is not a simple one and in the modern diet we also have an increased consumption of purine-rich meats, a high sodium intake and vitamin C can be limiting. We might get plenty of synthetic ascorbic acid which is used widely in the food industry but vitamin C activity is actually the result of a combination of thousands of other micronutrients working with vitamin C from natural sources (not a chemical lab). This is why no one should be taking synthetic vitamin C as a supplement. It is like buying new tyres for your car but never putting them on and still driving as though you have grip and braking power.
The result of the the above is that we now have a perfect storm for the development of obesity, diabetes, insulin resistance, hypertension, gout and cardiovascular disease.
The solution is discussed in my book, Wild Foods; Looking back 60,000 years for clues to our future survival.
If we supplement our diet with a wide range of wild and near-wild foods, several biochemical changes occur:
We lose our carbohydrate cravings and become sensitive to sweetness. White or milk chocolate, many sweets and desserts and so many fresh or dried fruits become too sweet to eat. This is a good thing if we listen to our taste buds and our microflora and choose less sweet foods.
We enhance our energy levels, both physical and mental, probably due in part, to better blood circulation facilitated by a reduced stickiness of our red blood cells. This improves blood flow and the exchange of gases, nutrients and wastes.
Our gut flora improves in speciation and numbers (consider that aspartame has been shown to kill our microflora, with just one dose able to reduce the numbers of our good micro-organisms by 50%).
Our immune system is boosted and gut flora fed high levels of organic acids (wild foods are typically sour) metabolize these into secondary products which have been shown to be anticancer.
The list goes on.
In fact, if you want another list, here is my Sugar List with 145 medical conditions that are brought on or made worse by bad sugars.