Sugar is a pretty hot topic in the nutrition world and one that is surrounded by a lot of bold statements. During my clinical rotations I heard patients say all types of things, from "Sugar causes cancer" to "I don't eat fruit because it has too much sugar." Now that I'm in the world of private practice and coming face to face with social media marketing and Instagram influencers, I see even more out there claims than before. I know that as a dietitian it can be confusing, so I can't imagine how the general public feels! My goal today is to give an unbiased education on all things sugar so that you can make an informed choice when it comes to your nutrition habits.
What is sugar?
When we think of the term sugar we think of table sugar or sucrose, a disaccharide made up of two sugars (glucose and fructose) bound together. However there are many more sugars (emphasis on the S) than just table sugar. When using the word sugars, we are referring to a broad category of all simple carbohydrates, aka mono- and disaccharides. Monosaccharides include glucose, galactose and fructose, and disaccharides include sucrose, lactose, maltose and trehalose. Sugars can be naturally occurring (found in fruits, vegetables, dairy products and nuts), they can be extracted from plants and dairy and added to foods, or they can be manmade using these foods as a starting point.
All carbohydrates break down to sugars, whether we’re talking about a potato, a cookie, or a banana. Carbohydrates or sugars are also our body’s preferred source of energy and the macronutrient that we are able to break down fastest. Of course, this all depends what the sugar is paired with...
Fructose vs Glucose metabolism
Of the three monosaccharides, glucose is the sugar that our body uses most. It is also the sugar we refer to when talking about diabetes and blood sugar (more on that later). Fructose, which is sometimes called “fruit sugar,” is a naturally occurring sugar found primarily in fruits (like apples, dates, figs, and pears). However it is also found in vegetables (like artichokes, asparagus, mushrooms, onions and red peppers), honey, sugar beets, and sugar cane.
When discussing sugar, often a conversation about fructose vs. glucose comes up. These two simple sugars are metabolized differently, in fact 90% of fructose is metabolized by the liver on the first go around, whereas glucose can be metabolized by many cells throughout our body. Both are transported into hepatocytes (liver cells) but have very different pathways once inside these cells. Since fructose cannot be used by our cells, over half is converted to glucose or glycogen (the storage form of glucose), some into lactate or carbon dioxide, and a small percentage (1-5%) is converted into free fatty acids. These free fatty acids are then packaged into triglycerides and carried through the bloodstream with very low-density lipoproteins. Though it only produces about 1g of fat per day, some researchers argue that this process can contribute to fatty liver and insulin resistance or increases in our hunger hormones and food consumption.
This leads us to High Fructose Corn Syrup (HFCS) which has been speculated to be more obesogenic than sucrose. Both sucrose and HFCS are made of glucose and fructose and the idea that HFCS contains considerably higher amounts of fructose is a misconception. Though there ARE some forms of HFCS than can go up to 90% fructose, the most common form is HFCS-55, which has only 5% more fructose than table sugar (table sugar is 50/50 fructose and glucose).
Both the Academy of Nutrition and Dietetics and the American Medical Association have issued statements concluding that there are no differences between HFCS and sucrose with regard to their likelihood of causing obesity. When it comes to obesity and weight gain, they have concluded that it all comes down to the increased energy consumption vs. any unique aspect of sugars.
Sugar and Chronic Disease
Diabetes is a disease that occurs when your blood glucose (aka blood sugar) is too high. It is diagnosed through your hemoglobin A1c, or a three month average of your blood sugar. There are two types of diabetes: Type 1 can occur at any age but shows up most frequently in children, while Type 2 (which accounts for 90% of cases) is more frequently found in adults. However, incidences of Type 2 in children have risen dramatically over the last 40 years, which is why the name was changed from Adult Onset Diabetes. There is also gestational diabetes, which occurs during pregnancy. Insulin, a hormone made by the pancreas, is a key player in diabetes. It usually helps glucose from food get into your cells to be used for energy, however with diabetes your body may not make enough insulin or doesn’t use it well. Glucose then stays in your blood and doesn’t reach your cells. This becomes a problem for many reasons- chronically high blood sugar being one of them, but another is the insulin. If our body is not using it properly, higher amounts can be released, which can lead to increased fat storage (as one of insulin's functions is to store fat).
When we think of diabetes, we often think of sweets- cookies, candies, ice cream, etc. However what is most important in this disease is balancing blood sugar and therefore monitoring overall carbohydrate intake- not just foods containing sucrose. Combining higher carbohydrate foods with those that contain protein, fat, and fiber and practicing portion control is the best way to manage your blood sugar through nutrition. Other non-nutrition ways to manage blood sugar are to exercise, increase daily steps, get adequate sleep and manage stress.
Can excessive carbohydrate intake lead to obesity? Absolutely. Is it the carbs or sugar alone that are the problem? Probably not. Most studies show that moderate sugar intake does not contribute to chronic disease when consumed in conjunction with normal calorie intake (vs. a caloric surplus). Worth noting, it is also hard to conduct research in this area because it would require several decades of highly controlled experiments on a large number of people, so we must rely more heavily on observational data or shorter clinical trials.
It is far more likely that one of the culprits in our country's rise in obesity is the increased access to hyperpalatable foods. These foods usually contain a combination of fat and carbohydrates with little protein or fiber and are therefore easy to eat in excess and create a caloric surplus without realizing it. In the end, a caloric surplus is the culprit when it comes to obesity, not the specific macronutrients or components like sugar. We must also remember that obesity is a very layered topic. There can be other contributing factors such as eating disorders, cultural beliefs and traditions, and limited access to nutritious foods due to socioeconomic factors like living in food deserts.
Types of Sugar
Added vs. Natural Sugar
Natural sugars, also called “intrinsic sugars”, are those that occur in fruit as fructose and dairy products as lactose. In general these tend to be paired with other nutrients that can assist in balancing blood sugar (like fiber, protein, and fat).
Added sugars refers to a category that includes a variety of sweeteners that have calories, including: table sugar, free mono- and disaccharides, sugars from syrup (like maple or agave) and honey, and sugars from concentrated fruit and vegetable juices. Added sugars do not include non- and low-calorie sweeteners.
Nonnutritive sweeteners, some of which are considered “artificial sweeteners”, are zero or low calorie alternatives to sweeteners with calories (like table sugar). Most are 100-300 times sweeter than table sugar but they do not raise blood sugar due to their lack of calories. There are some precautions to keep in mind for certain diseases (for example those with PKU should avoid Equal). However, a recent meta-analysis by Toews et al. (2019) showed that artificial sweeteners did not cause weight gain, increase cancer risk, or affect mood, cognition, or kidney function. There is some research indicating that the overconsumption of artificial sweeteners may negatively impact the gut microbiome, however that research is still immature. What we must remember is this: the dose makes the poison; consuming foods in moderation is generally a good rule to live by.
Myths about Sugar
Sugar is 8 times more addictive than cocaine.
This statement comes from a study that found that rats preferred water sweetened with sugar or saccharin over intravenous cocaine. There are many flaws with this study, including that it was done on rats and there’s no way to ethically replicate it in humans. Eating something you enjoy increases dopamine in the same way all pleasurable experiences do, but addiction and pleasure are not the same thing. While sugar can be habit forming, one does not experience withdrawal symptoms from it like they would with alcohol or drugs. There is no reliable evidence to support this claim.
Other sweeteners are healthier than sugar
Honey is lower on the GI index than sugar, meaning it won’t raise your blood sugar as quickly. It is also sweeter than sugar, so you may need less of it, however it is more calories per teaspoon. Raw varieties may include more vitamins, minerals, and enzymes, technically increasing the nutrient density of the sweetener, but it is still considered an added sugar and one we are encouraged to cut back on. Overall, the nutritional benefit from consuming honey over other sweeteners is negligible.
Agave nectar has been touted as a superfood replacement for table sugar, is 75-90% fructose. It is no healthier than other added sugar sources and has to undergo heat or enzyme treatment to convert it from complex carbohydrate to monosaccharide, so is technically more “processed”.
Coconut sugar contains some inulin (a fiber), but you would have to eat it in large amounts to make any difference. It also contains trace elements, potassium and sodium, but so do most other sugars (table sugar contains sodium and calcium and high fructose corn syrup contains sodium and iron). To see any benefits from the trace elements in coconut sugar, you would need to eat a large amount (causing a likely caloric surplus). Get your minerals from fruits and vegetables, not your sweetener, and use whatever sugar you prefer/is cost effective.
Sugar causes cancer
Foods with natural sugar actually play an important role in the diet of cancer patients or anyone trying to prevent cancer. In fact they provide essential nutrients that keep the body healthy and help prevent disease. This misconception may come from the idea that sugar leads to obesity, as obesity has been associated with certain cancers. It is important to keep the big picture in mind and eat a diet full of whole foods, quality protein, whole grains, healthy fats and fruits and vegetables.
Fruit (and some vegetables) have too much sugar
The bottom line is that fruit has natural sugar that is packaged with fiber, vitamins, and minerals (aka it has a high nutrient density) while table sugar, agave, etc are all high in calories and low in nutrients. The guidelines on added sugar are no more than 10% of your total daily calories from them (which equates to 200 calories or about 12 tsp for a 2,000 calorie diet). There are no limits on natural sugar. Evidence shows that the health risks from sugars, such as tooth decay and unhealthy weight gain, are related to consuming too many added sugars in the diet, not from eating sugars that are naturally present in fruits or milk. To put things into perspective, here are the nutrition facts on some controversial sugar sources vs. some added sugar sources:
If you truly feel you are exceeding upper limits and consuming too much natural sugar (you probably aren’t) try capping fruit at 2-3 servings per day (a serving = 1 cup raw).
What does this all mean?
The current literature provides little support for a unique relationship between consumption of sugar and chronic disease when sugar is consumed in a normal calorie diet (aka eating at your body’s maintenance calories and not in a great surplus). However, evidence does suggest that consumption of all energy dense nutrients (including added sugar) as well as decreased physical activity can create a caloric surplus, thereby causing weight gain and increasing the risk of chronic diseases.
Between 1970 and 2010 the average total energy intake in the USA increased by 474 calories per person. Almost all of this increased energy intake (about 94%) can be attributed to an increase in flour and cereal products and added fats, while added sugars only contributed 7% of the total increase. Multiple studies and meta-analyses have suggested that when sugars are substituted isocalorically for other carbohydrates and consumed in the normal range there is nothing unique in regard to sugar consumption and health consequences.
Sugar is not just table sugar- it is anything that breaks down to glucose, fructose, galactose
Natural sugar tends to come with more positives (fiber, vitamins and minerals) than added sugar
Sugar’s link to obesity, heart disease, cancer and other various illnesses is nuanced
Demonizing sugar only leads to overconsumption
Total calories are more significant than sugar in the context of your diet
Controversies about sugars: results from systematic reviews and meta-analyses on obesity, cardiometabolic disease and diabetes: https://link.springer.com/article/10.1007%2Fs00394-016-1345-3
Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses of randomized and non-randomized controlled trials and observational studies: https://www.bmj.com/content/364/bmj.k4718