Sugar has a characteristic sweet taste which nearly all mammals can detect. This isn’t surprising because glucose is a very good source of energy for the body and even more important than that, maintaining a constant level of blood glucose is crucial for survival.
Most sugars are produced by plants (Honey is the result of bees harvesting sweetness from plants, so it isn’t an animal source of sugar), an exception is the sugar lactose which makes milk sweet, which is of animal origin.
Sucrose (found in sugar cane, honey, sugar beet and sugar maple sap) and fructose (found in fruit) are the prime source of glucose (animals, including us, humans, can convert them into glucose). Both of them are sweet.
Starches and some short-chain polysaccharides (composed of multiple molecules of sugar) can also be broken down by our gut into glucose, but starches don’t have a sweet taste.
In the distant past, when food was scarce, finding a source of sugar was a bonanza: fruit or honey provided quick and tasty energy, but nowadays in the modern world, where food is over abundant and our lives are too sedentary, eating too much sugar can be a problem.
When we say “too much sugar” we don’t mean that people are eating too many apples, oranges or pears. Fruit has “natural sugars” and although you can also put on weight by eating too much fruit, the natural sugars in fruit are accompanied by fiber and vitamins which make them a healthy option.
Actually, the problem is the “extra” sugar that is added to processed foods. These “added sugars” are used to enhance flavor, provide texture, color and stability to foods.
As fat has been pinpointed as the main cause of obesity and heart disease (more on this below), the food industry has developed a full range of “low fat” or “reduced fat” foods.
But when you take the fat out of food, it becomes unpalatable and bland. So the food industry replaced fat with sugar!
The most common type of added sugar is known as High fructose corn syrup or HFCS, which contains roughly equal amounts of fructose and glucose and is found in yogurts, bread, salad dressings, crackers, ketchup, apple sauce, relish, cold cuts… you name it, and it will have added sugar.
Currently the intake of added sugars approaches 15 percent of overall energy intake in the average western diet.
And it is the added sugar that is being scrutinized by scientists who are trying to explain the wave of obestity and health risks associated with being overweight, that is flooding the world.
Because your body stores (as fat) all the unused refined carbohydrates (starch) and sugar that you eat.
Not all sugars are the same
Studies with rats (2) by Kanarek and Orthen back in 1982, showed that animals eating sugar plus a standard diet ingested more calories, gained weight and put on fat along their midsection in comparison to the rats eating a normal standard diet.
Rats eating sucrose plus the normal diet got fatter but didn’t eat more food. Rats eating other sources of sugar put on even more weight (sucrose solution, fructose solution and glucose solution).
The rats eating fructose solution had the highest levels of triglycerides in their blood, compared to the other groups.
The conclusion is clear: sugar intake makes you fatter, and somehow makes you feel more hungry, so you end up eating more.
To make matters worse, being fat is linked to a series of health conditions and an increased risk of disease (diabetes, cancer and heart disease).
But what about fat?
Nowadays we are warned to regulate our intake of fat, especially saturated fats. Fat has been blamed for the obesity epidemic and is demonized in most studies, however an overlooked fact is that back in the 1950s it was sugar that was under scrutiny: (3)
The first links between coronary heart disease (CHD) and sugar were detected in the 1950s. But the “Sugar Research Foundation” (SRF) whose members included growers and processors of beet and sugar cane across the US and also Canada and Haiti, quickly funded research projects which singled out fat as the cause of CHD, and at the same time covered up the evidence that showed that sucrose intake
was also a risk factor.
During the 1960s and 70s, the SRF actively funded, reviewed papers’ drafts and submitted them for publication but did not disclose that it was a sugar related food-industry funded foundation.
SRF’s efforts were successful, they portrayed fat as the main culprit of CHD, effectively clearing sugar from any suspicions of being a CHD risk factor.
The debate continues, but the picture that is emerging shows that sugar and refined starches (carbohydrates) play an important role in heard disease.
Let’s look into the health risks associated to eating too much sugar:
Obesity and sugar
As mentioned further up, we, mammals love sugar, but again, not all sugars are the same (4) Functional magnetic resonance imaging (fMRI) of the brain in human subjects
has shown that it responds differently to fructose or sugars containing fructose, when compared to glucose or a non-caloric sweetener such as aspartame.
Eating fructose leads to greater hunger and a desire for food than eating glucose does. Fructose seems to activate brain regions involved in reward processing, promoting appetite and feeding behavior. (5)
This confirms what Kanarek and Orthen had first found in rats in 1982: fructose makes you feel more hunger, so you will eat more and put on more weight.
But sugar also triggers other mechanisms that make us put on weight (6) it promotes insulin resistance, leading to high insulin levels which cause obesity (insulin is a fat-storing hormone).
Fructose causes the cells that metabolize it, to get inflammed, and when fatty cells under the skin metabolize fructose, this inflammation provokes the release of cortisol -as your body reacts to calm this inflammation. However cortisol has an unpleasant side effect: it displaces the fatty acids from these subcutaneous fat cells and moves it into the abdominal cavity, padding the internal organs with visceral fat.
As a result of this inflammation visceral fat increases considerably (Read more about the Dangers of Belly Fat at our website).
Another study with mice (9) found that eating high fructose corn syrup lowered the secretion of dopamine in their brains. Lower dopamine function is linked to compulsive behaviors (such as compulsive eating) and to lower energy expenditure. So the sugar makes mice eat more and burn less energy, making them gain fat and weight.
Nonalcoholic Fatty Liver Disease (NAFLD)
If fructose is metabolized in the liver, this inflammation causes fatty liver (more fat is stored inside the liver itself). (6)(1)
At one time NAFLD was believed to be the consequence of a sedentary lifestyle and overeating, but new evidence suggests that “diets high in sugar -from sucrose and ⁄ or high fructose corn syrup (HFCS)” increases the risk for NAFLD.
Your Gut’s microbiota is also altered
Studies with mice (7) found that high-glucose or high-fructose diets could increase insulin, fat mass and blood sugar levels without necessarily increasing body weight. These mice were “Thin on the outside but fat inside”, a very nasty tipe of thinness.
The extra sugars that the mice ate altered the microbes that colonize their digestive tract and this provoked intestinal permeability and a condition known as “metabolic endotoxemia”, which causes an increase in pro-inflammatory chemicals and free-radicals which promote inflammation, accumulation of fat and fatty-liver as observed in cases of “normal-weight obesity”.
Alzheimer’s disease and sugar
A study by Pase et al., (2017) (8), reports that “Excess sugar consumption has been linked with Alzheimer’s disease (AD) pathology in animal models“, the extra sugar came from
drinking sugary beverages (such as fruit juice -not fresh fruit, but sugar added juice).
Drinking more than one sugary beverage per day was associated with a “lower total brain volume… poorer performance on tests of episodic memory… lower hippocampal volume” and these are markers of precinical Alzheimer’s disease.
Sugar is addictive
Another study (10) which used animals, found that sugar produces symptoms associated to addictive substances such as bingeing, craving, tolerance and withdrawal effects, reward and opioid effects, among others.
Apparently from the point of view of brain neurochemistry, in animals and humans sugar abuse and drug abuse have similar effects.
The cause seems to be the natural opioids released by the brain when sugar is eaten (yes, the sweet taste gets you high on your own endogenous opioids!).
Coronary Heart Disease and sugar
A study by James DiNicolantonio and James H O’Keefe (2017)(11) reports that one out of every six deaths in the USA is caused by coronary heart disease (CHD), and overconsumption of added sugars, has been associated with an increased risk of CVD and mortality due to cardiovascular causes.
DiNicolantonio and O’Keefe state that there is a relationship between insulin levels and risk of cardiovascular disease, and that it is independent of blood pressure, blood sugar and blood lipids. As refined sugar makes insulin levels spike (much more than starch for instance), they say that “this provides compelling evidence that overconsuming added sugars (sucrose or high-fructose corn syrup) may lead to an increased risk of CHD through raised insulin levels.”
The good news is that a diet low in added sugar and refined carbs reverses these metabolic problems.
Which brings us to the otucome of a Finnish study involving 4,842 adults aged 25 to 74 years (12):
- Younger people eat food with more added sugar and less natural occurring sugar (less fruit for instance) than older people.
- People eating more added sugar tended to eat less fiber
- And they also ate less fruit (women) and vegetables (men).
- Higher added sugar consumption was associated to higher butter consumption (more sugars and more fats).
- More intake of naturally occurring sugars was linked to an overall healthier lifestyle (more physical activity, less smoking).
Fat, as a nutrient, and specially saturated fats, has been blamed for obesity and the health risks associated with it. However since the 1950s, sugar has been known to increase heart disease risk and cause weight gain.
Effective lobbying by the sugar industry in the US managed to shift the focus from sugars to fats and in the process remove fat from our processed foods and replace them with “added sugars”.
These added sugars now account for around 15% of our daily caloric intake, and they are present in almost every single processed food that we eat, from ketchup to salad dressing, from crackers to cold cuts.
Among these added sugars is high fructose corn syrup, which, as we have seen further up is linked to obesity, visceral fat, fatty-liver, an increased risk of Alzheimer’s disease. It is an addictive substance
that makes you eat more (not only sugars, but all types of food) and feel hungrier, it also makes you burn less energy. The perfect mix for obestity and the chronic health conditions linked to it: diabetes and heart disease.
The best option is to eat a healthy and balanced diet, with the right mix of nutrients, including fruits which have “naturally occurring sugars” and fiber, whole grains, vegetables and less red meat and more fish.
Keeping physically active will also help control weight, feel better and improve your wellness.
Sources and Further Reading
(1) Jensen T, Abdelmalek MF, Sullivan S, et al. (2018). Fructose and sugar: A major mediator of non-alcoholic fatty liver disease. J Hepatol. 2018;68(5):1063-1075
(2) Kanarek RB, Orthen-Gambill N. (1982), Differential effects of sucrose, fructose and glucose on carbohydrate-induced obesity in rats. J Nutr. 1982 Aug;112(8):1546-54.
(3) Cristin E. Kearns, Laura A. Schmidt, Stanton A. Glantz, (2016). Sugar Industry and Coronary Heart Disease Research – A Historical Analysis of Internal Industry Documents. JAMA Intern Med. 2016;176(11):1680-1685. doi:10.1001/jamainternmed.2016.5394
(4) Murray S, Tulloch A, Criscitelli K, Avena NM., (2016). Recent studies of the effects of sugars on brain systems involved in energy balance and reward: Relevance to low calorie sweeteners. Physiol Behav. 2016;164(Pt B):504-508
(5) Luo S, Monterosso JR, Sarpelleh K, Page KA., (2015). Differential effects of fructose versus glucose on brain and appetitive responses to food cues and decisions for food rewards. Proc Natl Acad Sci U S A. 2015;112(20):6509-14
() DiNicolantonio JJ, Mehta V, Onkaramurthy N, O’Keefe JH., (2017). Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity. Prog Cardiovasc Dis. 2018 May – Jun;61(1):3-9. doi: 10.1016/j.pcad.2017.12.001. Epub 2017 Dec 8
(7) Do MH, Lee E, Oh MJ, Kim Y, Park HY., (2018). High-Glucose or -Fructose Diet Cause Changes of the Gut Microbiota and Metabolic Disorders in Mice without Body Weight Change. Nutrients. 2018;10(6):761. Published 2018 Jun 13. doi:10.3390/nu10060761
(8) Pase MP, Himali JJ, Jacques PF, DeCarli C, Satizabal CL, Aparicio H, Vasan RS, Beiser AS Seshadri S., (2017). Sugary beverage intake and preclinical Alzheimer’s disease in the community. Alzheimers Dement. 2017 Sep;13(9):955-964. doi: 10.1016/j.jalz.2017.01.024. Epub 2017 Mar 6
(9) Meyers AM, Mourra D, Beeler JA., (2017). High fructose corn syrup induces metabolic dysregulation and altered dopamine signaling in the absence of obesity. PLoS One. 2017;12(12):e0190206. Published 2017 Dec 29. doi:10.1371/journal.pone.0190206
(10) James J DiNicolantonio, James H O’Keefe1, William L Wilson, (2018). Sugar addiction: is it real? A narrative review BJSM, july 2018. Vol 52:14.
(11) James J DiNicolantonio and James H O’eefe, (2017). Added sugars drive coronary heart disease via insulin resistance and hyperinsulinaemia: a new paradigm. BJSM, November 2017, Vol 4:2
(12) Kaartinen NE, Similä ME, Kanerva N, Valsta LM, Harald K, Männistö S, (2017). Naturally occurring and added sugar in relation to macronutrient intake and food consumption: results from a population-based study in adults. J Nutr Sci. 2017;6:e7. Published 2017 Mar 8. doi:10.1017/jns.2017.3
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