Nitish Sharma, experienced biotechnologist on Kolabtree, writes about sugar alternatives and rare sugars that can be used to substitute the “sweet poison”.
Our food habits have evolved systematically since pre-historic times, from the time of hunter-gatherers to pastoralism and agrarian culture. The desire to eat more than we require is fueled by several factors, including the taste and aroma of food itself. However, any disproportionality in food intake or excessive consumption of certain foods can have severe adverse effects on our health. We are currently in a state of indecision about whether or not to eat sugar, though we love it all the same! Our love of sugar can be measured by the consumption per capita and availability of an extensive variety of artificial sweeteners in the market. Although the importance of sugar can’t be surpassed, its ill effects should not be ignored either. Food scientists are working hard to find sugar alternatives. Let’s examine some of the substitutes, especially rare sugars.
Sugar: a sweet poison for silent killing
The fuel that runs the complex metabolism of the body is food. It is essentially composed of proteins, carbohydrates, fats, vitamins, minerals and some other nutrients . Our food has various components, but saccharides have a prime position due to their energetics and their sweet taste.
Carbohydrates/saccharides are an indispensable and essential part of food that sustain growth and helps conduct vital processes to furnish the energy requirements of the body. Though all saccharides are not sweet, most of mono- and di-saccharides taste sweet after the action of certain specific enzymes like salivary amylases. Some polysaccharides also taste sweet, such as starch and cellulose. On the molecular level, glucose and fructose mostly contribute to the sweetness of saccharides; in these, hydroxyl (-OH) groups are arranged in a specific way that enables our olfactory buds to taste sweet . The sources of sugars are natural like fruits, veggies, and milk, and unnatural like added sugars e.g. sucrose available in the form of processed foods like candy, cakes, jellies, fruit juices, etc. Sugars rich in fructose like high fructose corn syrup are known to enhance the desire to eat more by increasing the level of hormones Ghrelin and reducing the level of Leptin which signals us to stop eating .
Sugar takes an important place in our cultures and rituals, and in most parts of the world, sweets are more ceremonial than just a component of food. Undoubtedly they are important for energy metabolism and ultimately to run a body metabolism properly. But they also possess some threats. According to the American Heart Association (AHA) the minimum requirement of sugars per day is ~150 Calorie (37 g) in the case of men and ~100 Calorie (25g) per day for women . But actual uptake is several times more that of the minimum requirement. Packaged foods are the instant source of added sugars and over-consumption increases the blood glucose level immediately. Prolonged consumption of added sugar leads to different diseases like diabetes, obesity, tooth decay, cardiovascular, non-alcoholic fatty liver, and a certain type of cancers also . These diseases are the result of our behavior due to an imbalanced diet. There are also many emotional factors and mental stress factors associated with sugar addiction.
There might be many causes of increasing sugar consumption but the consequences are severe. Moreover in this 21st-century fatality rate is somewhat high due to the addition of sugar and its derivatives, as shown in a previous study published in the reputed American Journal of Clinical Nutrition . In this particular study, the authors have drawn a rough sketch between sugar intake and mortality rate in the Swedish population. But the relevance of this study is not limited to a particular area and has global impacts. Though sugar has become a part of our metabolism and is essential for instant energy, the ill effects urge us to search for the sugar substitute for mankind.
Sugar alternatives: Nature’s weaponry against the sweet poison
Just like nature has provided solutions to so many other problems, it already has substituted for sugar hazards, as it harbors rare sugars like D-psicose/ D-allulose, D-tagatose, L-sorbose, apiose, allose, steviol, erythritol, xylitol and many more. These sugars not only satisfy our taste buds but also have a low calorific value. Due to this, their sweet taste, and rare side effects, they are a fantastic substitute to sucrose and synthetic sweeteners as well. Furthermore, as they are mostly of plant, animal and microbe origin, they have little chances of any medical problem. Most of them have GRAS (generally regarded as safe) status from competent authorities like FDA  but only a few of them have been commercialized due to their recent discoveries and low fanfare. The major cause behind the rapidly increasing obese and diabetic population is the lack of public awareness. Because substitutes for table sugars are not readily available in the market and do not even get prioritized by the consumers due to their high cost and some misconception about their use. On the other hand, sugar and its adulterated forms are available in shops at the cheapest rates. Which makes them the ultimate choice of the consumers. Below are some examples of rare sugars a few of them are available in the market and many are yet to be. These are promising candidates against the possible fatal sugar outbreaks in this century:
1. Steviol glycosides
Steviol glycosides are diterpenoid glycosides isolated from the leaves of the plant called Stevia rebaudiana native to South America (now grown worldwide). These compounds are generally produced as the Steviol in the plant metabolism. Glycosides are ~100 times sweeter than the normal and have very less calorific value to the sucrose. They not only are sweet but also exert some health benefits like maintenance of low blood pressure, hypertension, lowering blood sugar level, reducing the synthesis level of low-density lipoproteins (LDL), and inhibiting the formation of clots inside the arteries.
It is another kind of natural substitute for table sugar. It has ~70% sweetness to the sucrose but only 0.24 kcal per gram as compared to the sucrose which provides ~4 kcal per gram. It is sugar alcohol generally found in fruits. But apart from its immense health benefits similar to glycosides it sometimes causes problems in the digestive system, especially on overeating.
It is also a sugar alcohol found in many plants especially in Birch (Betula L.) wood plant which is used to prepare the medicines. It generally provides the ~2.4 kcal of energy per gram which is less than half of provided by the sucrose. However the sorbitol is a prominent substitute for the added sugars in candies and gums but xylitol has more benefactions like diabetes control, prevention against the otitis media, sinus problems and prevention in tooth decay (not utilized by oral microflora to convert it into acids). Like other sugar substitutes, xylitol is also to be consumed in limited quantity (~50g/day), as taking a higher dose can cause diarrhea, intestinal gas and in some prolonged conditions tumors also (8). So it is advisable to use it in permissible quantity.
4. Yakon Syrup
A green food product is more probiotic than a sweet substitute and a relatively new ammunition against the conventional sugars. It is also known as nectar and prepared from the roots of the plant Yacon (Smallanthus sonchifolius). It is rich in fiber content and also composed of fructooligosaccharides, inulin, and glucose-fructose in very less quantity (9). It provided fewer calories than sucrose and have half of the sweetness to it. Due to its low glycemic index, it also regulates the blood sugar level and insulin metabolism. In a few studies, it is also marked as a tremendous supplement for weight loss. But as with other sweeteners, Yakon syrup can also cause trouble on overconsumption like diarrhea, abdominal ache, and bloating. The permissible limit for its consumption is ~20g/day to avoid any type of medical side-effects.
These are some examples of the sugar substitutes available in the market under different brand names and most people are familiar with their names. But below are the examples of the sugars which can be named as the true “rare sugars”. Most of them are still anonymous but they are surely the sugars of the next generation.
Rare sugars: Promising substitutes?
It is also known as D-ribs-2-hexulose and is a C3 epimer of the fructose. Fructose is a pentose sugar and sweeter than glucose and present in a 1:1 ratio in sucrose. Fructose has different fates inside the body and plays a crucial role in its proper functioning but it is also responsible for the enhanced craving for the sweets and interference with insulin metabolism. Allulose is an excellent substitute for the fructose. It was discovered more than 70 years ago in the wheat and is certainly present in some food in very little quantity. It has 70% sweetness like that of the sucrose and a very less amount of calories i.e. ~0.2 kcal per gram. Due to this, allulose has a negligible glycemic index. The major problem associated with allulose is its production, as it is present in the negligible amount in fruits, grains, in some natural products such as honey and few microbes also. Recombination DNA technology has provided some sort of solution to this and the genes associated with proteins responsible for the interconversion of fructose into the allulose are cloned and expressed heterologously for mass production of allulose form different sources containing fructose. D-allulose has the GRAS status from the FDA, but still, its use is banned in the European Union and other countries. Japan is the only country where the consumption of D-allulose is being granted in the public domain.
It is also an isomer of the fructose and has 90% sweetness to the sucrose. Very less amount of the D-tagatose gets metabolized in the liver and has scarce calorific value. D-tagatose has the GRAS status also and used as a sweetener in many food items like candies, beverages, yogurt, creams, and cakes in some countries like the European Union, etc. The production of the D-tagatose is not restricted to the fructose isomerization only but it can be synthesized by the chemical catalysis of the D-galactose in the presence of the metal hydroxides (10). The impact of the D-Tagatose on health is quite beneficial as it lowers the blood glucose level, inhibits the hepatic glycogenolysis and increases in the accumulation of the high-density lipoproteins (HDL) cholesterol. It also acts as the antihyperglycemic, antidiabetic agent hence a potential candidate for the treatment of obesity (11).
It is a ketose isoform of the D-Fructose sugar. In nature, it generally found in the L form and synthesized by bacterial (Acetobacter sp.) fermentation of sorbitol. It often used for the production of the Ascorbic acid (Vitamin C) on the industrial scale (12). Its sweetness is equivalent to the table sugar and has little gastric discomfort on excessive consumption due to its slow absorptivity in the intestine. Though there is no report of L-sorbose affecting the lipid metabolism it lowers the glucose level in plasma and interferes with insulin metabolism positively.
It is an aldohexose sugar and C3 epimer of glucose. Its availability in nature is rare and only reported in the African shrub called Protea rubropilosa as a 6-O-cinnamyl glycoside and in the fresh-water alga known as Ochromas malhamensis. Its exact concentration in the biome is unknown and it is soluble in water and experimentally inexplicable in methanol. It has only 80% sweetness to the table sugar but explicitly low calories per gram which makes it an exceptional counterfeit to the sucrose and other synthetic artificial sweeteners.
The rare sugar apiose present in the cell wall polysaccharides of the higher plants. One example of this is the apiosylated galacturonans of pectins in plants. Apiose is an unusual monosaccharide and is alluring for scientists from more than a hundred years (13). The apiosylation of the secondary metabolites of plants is still a matter of research but apiose has already become a sugar with extra benefits. Due to the presence of different sugars especially rare sugars like apiose in the hairy rhamnogalacturonan region of pectin, it is useful to prepare the low-calorie jams. No authenticated research data is available on the sweetness, calorific value and glycemic index of the apiose (13). But some independent studies done using apiose indicated it as a potential candidate for sugar-free society. The severity of sweet dependence is increasing rapidly. We have an increased threshold of obesity and cardiovascular diseases in our population. Rare sugars can be a concrete solution but firstly we should change our priority.
And what about the artificial sweeteners?
As we are discussing this today we have a well-established industry of artificial sweeteners and it is still growing gradually. The artificial sweetener market is estimated to expand at a CAGR of 5.05% to reach US$9.704 billion in 2024 from US$7.22 billion from where it was last year (14). We have a huge variety of artificial sweeteners, e.g., Aspartame, Adwantame, Neotame, Sucralose, etc. They usually are 2000 to 20000 times sweet to the table sugar with less calorie and negligible glycemic index (3). Even though they have many good effects on health like, good for weight loss (known to reduce the appetite), enhance the gut microflora, provide immunity to the metabolic syndromes and up to a certain extent they help to curb diabetes (especially type II). However, despite its benefits, the interaction of the artificial sweeter and our body is complex. Let’s take an example of Aspartame only, which is an FDA approved artificial sweetener (5). There are certain reports which have shown the relatively high headache, depression, and seizures in some peoples after regular consumption of the aspartame (5). In the case of a person suffering from diseases like phenyl ketone urea (PKU), it is not advisable to consume aspartame. In another study, the craving for eating more sugar has also been reported after consuming synthetic sugars. The side effects cannot be underestimated when food is related because any negligence do permanent damage to not only our health but also future generations.
The message to take home
Sugar is an immortal and unavoidable component of our food. Sugar is not troublesome in itself but its overconsumption has a severe impact on health. The demand for alternate sugars has become a need of the hour. It is good we are already searching for sugar substitutes and we even have some potential candidates. The biotech industry has a crucial role to play here because the world population is growing so are the diseases. It will be a crucial task for the industry also to provide a variety of rare sugars to fulfil its demand with no compromise to quality. Artificial sweeteners provide some sort of benefits but they are not “magic bullets” and have severe health impacts also. Rare sugars are the ray of hope. Sugar has been the part of the cultural evolution of many civilizations and also a major driving force for globalization. There is no doubt that the sugar has driven the tasteful evolution of humans from insipid to its delicious present. Needless to say that rare sugars are essential to create a world that can still enjoy the taste of sugar without a negative impact on health.
- Alternative sugars: Yacon syrup (nectar). Br Dent J 223, 625 (2017) doi:10.1038/sj.bdj.2017.943.
- Kim, “Current studies on biological tagatose production using L-arabinose isomerase: A review and future perspective,” Applied Microbiology and Biotechnology, vol. 65, no. 3, pp. 243–249, 2004.
- Marion Guerrero-Wyss, Samuel Durán Agüero, and Lisse Angarita Dávila, “D-Tagatose Is a Promising Sweetener to Control Glycaemia: A New Functional Food,” BioMed Research International, vol. 2018, Article ID 8718053, 7 pages, 2018. https://doi.org/10.1155/2018/8718053.
- Würsch, P., Welsch, C. and Arnaud, M.J., 1979. Metabolism of L-sorbose in the rat and the effect of the intestinal microflora on its utilization both in the rat and in the human. Annals of Nutrition and Metabolism, 23(3), pp.145-155.
- Pičmanová, M. and Møller, B.L., 2016. Apiose: one of nature’s witty games. Glycobiology, 26(5), pp.430-442.
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