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Sugar: as bad as we thought?


It sneaks in everywhere, hiding behind a long list of different names and clever disguises. It creeps into tomato sauce, lurks in every salad dressing, and infiltrates otherwise-innocent canned soups. Even bacon isn’t safe! If you spend any time at all on Paleo, you practically start to see sugar peering out from behind every corner, shrouded in a black trench coat and hatching nefarious schemes to trap you in its clutches.

Assigning personality to a food can itself be unhealthy, but in this case, the food doesn’t even deserve all its bad press. Of course, like any other food, sugar is unhealthy when eaten to excess, or when eaten in a processed, refined, and artificial form. Some people would do better to avoid it – just as some people would do better to avoid nightshades, dairy, or eggs. But in the context of a diet rich in nutrients, sugar – especially sugar from whole foods like fruit or dairy – is not the kiss of death.

What Is Sugar?

Most of us think of “sugar” as the white powder we like to add to our coffee, but in biological terms, sugar is nothing but the building blocks of carbohydrates. Sugars come in several different types, including single sugars and double sugars (combinations of two single sugars). Since your body digests them all differently, the distinctions among all these types of sugars are actually quite important.

Any food with a carb content greater than zero will have some sugar in it. Even foods we don’t usually think of as “sugary,” like potatoes, contain sugar in the form of glucose. Refined foods like white flour and table sugar are called “simple carbohydrates” because their molecular structure includes single or double sugars. Whole grains and legumes are called “complex carbohydrates” because they’re made of three or more sugars. When you eat simple carbohydrates, your body can use them for energy right away (this is why you can get a “sugar rush” from eating too much candy); when you eat complex carbohydrates, your body has to break them down into simple carbs first. Since this process takes some time, most people don’t get the same immediate rush of energy from complex carbohydrates.

The role of these complex carbohydrates, also called starches, in the diet is itself a fascinating topic, but this article will focus on simple carbohydrates and the way we break them down. Understanding what sugar is, and the different forms that it can take, is important for everyone attempting to maintain a healthy diet in the face of the post-industrial food environment. As sugar has come under intense scrutiny for potentially contributing to the modern obesity crisis, this knowledge can help us interpret the reams of conflicting studies and chart a sane and healthy course between binging on Jolly Ranchers and panicking over every strawberry.

Sugar and the Science of Obesity

The number of studies on the relationship between sugar and weight gain is enormous, but unfortunately, this mass of scientific literature has not managed to produce anything like a consensus. The studies that exist are frustratingly inconclusive, and seem to contradict each other more than they agree. An hour of searching for scientific studies will give you a huge pile of evidence that sugar is the underlying cause of every modern health problem, and an equally huge pile proving that sugar is actually harmless – in some rodent studies, a higher sugar intake even appeared to promote leanness!

Making sense out of this huge mass of contradictory data is daunting. One fairly comprehensive review of studies on sugar and weight gain concluded that the decisive factor is not sugar, but calories: only hypercaloric trials (trials where sugar intake caused a net increase in caloric intake) produced weight gain, and that this might just as easily be due to the calories. Thus, it’s important to separate the effects of sugar specifically from the effects of simply adding calories to the diet.

This is especially true if the subjects are already overeating, as in this study. In a conclusion that shouldn’t surprise anyone, scientists discovered that a group of overweight and obese adults experienced all kinds of negative effects (including weight gain and metabolic damage) when they added sugar-sweetened beverages to their diet as 25% of their daily calories. However, this study is a perfect illustration of the many complexities involved in determining the effect of sugar in the diet. First, obese people are already metabolically deranged: people with a healthy metabolism might not react the same way. Second, 25% of calories is nowhere near a moderate sugar consumption; finally, the consequences of drinking highly processed sweetened beverages do not necessarily extend to natural sources of sugar like fruit.

All of these confounding factors suggest that something much more complicated is at work than the simplistic idea that “sugar makes you sick and fat.” Anthropological studies of traditional hunter-gatherer diets have also failed to find a conclusive link between sugar and health problems: while some hunter-gatherers do eat a diet very low in sugar, others, such as the Hadza in Tanzania or the Kuna in Panama, eat a diet fairly high in sugar without any noticeable difference in health or body composition.

The reams of contradictory evidence about sugar consumption make it clear that just talking about “the effect of sugar on the body” is very imprecise, because it fails to specify three very important points. What type of sugar, how much, and whose body? The effects of sugar also depend on what kind of food you get the sugar from: chugging a liter of Coke is a world away from eating an orange, even though they both contain sugar. Making a blanket statement about how all sugar is always harmful for everyone sounds very tough-love and inspiring, but it isn’t necessarily true.

What Type of Sugar, How Much, and Whose Body?

As noted above, “sugar” is a term that can actually refer to one of several different compounds. Table sugar is just one of these compounds. Instead of assuming that all types of sugar are the same, it’s important to read any research on “sugar” with a crucial question in mind: what kind?

As noted above, sugars are generally separated into two broad categories: single and double. Single sugars include glucose (found in fruits and starchy carbohydrates), fructose (found only in fruits), and galactose (found in dairy). Double sugars are combinations of these single sugars: one very common double sugar is sucrose (table sugar), which is a 1:1 mix of glucose and fructose. Lactose is a mixture of glucose and galactose. High fructose corn syrup sounds like it should be 80 or 90% fructose, but the ratio of glucose to fructose that it contains is closer to 1:1. Honey is another double sugar, but the ratio of glucose to fructose in honey varies, depending on the bees that produced it.

Each different single sugar is digested differently. Glucose, for example, can be sent directly into your muscles and other cells, and either used immediately or stored as glycogen for future energy. Fructose, on the other hand, needs to be processed by your liver first, and either turned into fat (in a process called de novo lipogenesis) or glucose. Because it’s harder to metabolize, many people have trouble digesting fructose, while negative reactions to glucose are much less common. Seeing fructose metabolism as nothing but a less efficient way of getting glycogen, many Paleo researchers have concludes that fructose is the “bad sugar.” Glucose (the sugar found in “safe starches” like yams and white rice) might be acceptable, but fructose is out.

The problem with this approach is that it ignores another important question: how much?

Excess sugar or a huge dose of fructose is clearly harmful. If nothing else, eating too much sugar makes it very easy to eat too many calories – especially if you get that sugar through sweetened drinks that don’t fill you up for very long. Metabolizing large amounts of sugar, especially fructose, is also stressful to the body: too much fructose can put a heavy strain on your liver, and cause oxidative stress and inflammation. Excess fructose interrupts your normal production of leptin (the hormone that tells your body when to stop feeling hungry), making it very easy to gain weight. Too much sugar of any kind – glucose or fructose – can also lead to all the problems of a high carbohydrate diet: insulin resistance, weight gain, inflammation, and diabetes.

Eating too much sugar is dangerous, but this doesn’t necessarily prove that any level of sugar consumption is bad: eating too much of anything is problematic. Vitamin A could also be considered a “dose-dependent toxin” (something that harms your body if you eat too much of it), but this doesn’t mean we should avoid it altogether!

So how much sugar is too much for the body to process safely? The answer depends on yet another question: whose body? Many foods do not have the same effect on everyone who eats them. A perfect example of this is dairy. If you don’t have the gene that allows you to produce lactase, the lactose in dairy can make you feel very sick. If you do have that gene, you can enjoy dairy products without a problem. So it’s silly to say that dairy is a “safe food” or a “harmful food:” whether it’s safe or harmful depends on the person eating it.

In many ways, the same is true of any kind of sugar. Since digesting sugar requires a healthy metabolism and a certain degree of insulin sensitivity, the upper boundary of a healthy sugar intake is probably much smaller for people who already have trouble with insulin metabolism, such as diabetics or people who are already obese. On the other hand, people with a healthy metabolism might not have any problems digesting a moderate amount of sugar.

As with any carbohydrate, the amount of sugar that you can eat healthily also depends on your activity level: very active people frequently burn through the glycogen stored in their muscles, so when they eat carbohydrates, the glucose goes to replenishing the glycogen stores, not to creating fat. On the other hand, sedentary people need to be much more moderate with their carb intake, since they don’t have as great a need for glucose in the diet.

Additionally, some people with specific digestive disorders should avoid certain types of sugars. People with Irritable Bowel Syndrome (IBS) very frequently suffer from a problem called fructose malabsorption, an intolerance to fructose that can cause a variety of digestive problems. In this case, avoiding fructose can provide significant relief of IBS symptoms. People sensitive to FODMAPs should avoid foods high in fructose and several other types of sugars like sugar alcohols, since these can irritating to the gut. It can also be beneficial to steer clear of sugars in general if you’re struggling with an overgrowth of harmful gut bacteria like Candida: since sugar is these bacteria’s favorite food, avoiding it can help get your gut flora back under control.

Sugar rushPhysical problems aren’t the only reasons why someone might want to avoid sugar. It can also be a very problematic food for anyone recovering from a binge eating disorder. Switching to a Paleo diet high in nutrients and cutting out all food toxins and processed foods can do a world of good for your body, but it doesn’t remove the emotional and psychological issues that underlie an eating disorder. It’s not uncommon for recovering binge eaters to have trouble moderating their intake of some foods on Paleo, and foods high in natural sugars (like fruits) are among the most problematic. Thus, if you’re recovering from an eating disorder, it might be helpful to restrict your sugar intake, at least at first.

In short, the answer to “What effects does sugar have on the body?” is, “It depends.” It depends on what kind of sugar, how much of it, and exactly whose body. An overweight, diabetic, and sedentary office worker digesting a bowl of ice cream and a lean, healthy athlete digesting a bowl of strawberries are both, technically, metabolizing sugar. But these two situations are so different that they barely deserve the same name.

Where is it From?

The example above illustrates another important consideration with sugar: how you get it. Think of the difference between meat and protein shakes. There’s nothing wrong with eating meat that contains protein, but protein powders and shakes are generally harmful. Why? Because protein powders provide protein in an artificial, processed, and highly concentrated form that our bodies don’t digest well, accompanied by a hefty wallop of preservatives, sweeteners, and other chemicals. There’s nothing wrong with eating protein, but where you get it from matters. The same is true for sugar. People don’t eat pure fructose or galactose; they eat foods, and foods have much more to them than sugar.

First, some sugar-containing foods also contain other valuable vitamins and minerals: one orange, for example, contains 12 grams of sugar, but also significant amounts of Vitamin C, Folate, Calcium, and Potassium. Four ounces of Coke provide the same amount of sugar, no vitamins or minerals, and a Nutrition Facts label full of unpronounceable chemicals and additives. It shouldn’t come as a surprise that the orange and the Coke will have a very different effect on your overall health – especially since many people eat one orange and then stop, while almost nobody drinks just 4 ounces of Coke at a time (a standard can is 8 ounces; a bottle is 20 ounces).

Studies that try to link sugar and obesity seem to have come to the same conclusion. Natural forms of sugar don’t appear to be reliably linked to obesity; the problem comes with refined and processed forms like high fructose corn syrup. Most studies that attempted to correlate overall sugar intake with weight gain in humans couldn’t find a clear connection, but sugary drinks (which contain very highly processed sugars) were clearly linked to a higher rate of obesity. This is why hunter-gatherers eating traditional diets can include sugar as a high percentage of their daily caloric intake, but stay lean and healthy with none of the metabolic problems associated with the first world. Many of these groups are even famous for the great efforts they make to get honey – and yet they don’t see the same health problems from it as we see from the sugar in Coke and Skittles. In other words, where you get your sugar matters.

One possible explanation for this has to do with food reward. As discussed in a previous article about obesity, the food reward theory states that “hyperpalatable” foods (processed food products that present us with tastes and textures much more intense than anything found in nature) cause obesity because they confuse our natural appetite regulation systems. Highly processed foods and beverages definitely fall into the category of superstimuli that we aren’t designed to handle. Fruit and other natural sources of sugar, on the other hand, are not hyperpalatable, so they don’t cause the same negative metabolic reaction. One study even fed the same sugar water to two groups of mice: one group that was capable of tasting sweetness, and another group that wasn’t. The group that could taste sweetness got fat; the group that couldn’t, didn’t.

Whether or not the food reward theory can adequately explain the difference between natural and artificial sugars, it’s clearly important to consider what kind of foods we get our sugar from. Sugary drinks do promote obesity, but this doesn’t mean that a whole, natural food like a banana will have the same metabolic effect as a glass of soda loaded with all kinds of refined and processed chemicals.

Table Sugar Substitutes: Other Natural Sweeteners

Since processed sugar is so much more harmful than natural sugar from whole foods, one common question about refined table sugar is whether other, more natural sweeteners are preferable. The idea of these foods as “sugar substitutes” is somewhat misleading, since common “sugar substitutes” like honey and maple syrup do also contain sugars. We’ve chosen to refer to one type of sugar as “sugar” and another type as “honey,” but in the end they’re both biologically made up of sugars. All natural sweeteners contain some form of sugar, even if we call them by another name.

Nevertheless, some replacements for table sugar do have other advantages that are worth noting. Honey, for example, has several beneficial compounds (although the specific content will depend on the flowers available). Chemically, honey is approximately 40% glucose, 36% fructose, and 24% other sugars, although the exact proportions vary depending on what the bees ate. While the high fructose content can cause trouble for some people with fructose malabsorption problems, the fructose in honey is accompanied by an equal amount of glucose, which makes it much easier to digest. Furthermore, honey has the advantage of a long evolutionary history: humans have been going to incredible lengths to get it since we figured out how delicious it was. Several preindustrial peoples consumed a significant percentage of their daily calories from honey on a regular basis: one 10,000-year-old painting from Spain shows two men gathering honey from a beehive. Raw honey (as opposed to pasteurized honey) is also a completely unprocessed food, while even other natural sweeteners like maple syrup and molasses require some processing.

If there’s any such thing as a “Paleo sweetener,” honey is probably it. But honey is far from the only naturally-occurring sweet substance. Maple syrup is relatively low in fructose (making it a good option for the fructose-intolerant), and contains manganese, potassium, iron, and calcium. Molasses is essentially table sugar, but with nutrients: it contains minerals like iron, calcium, and magnesium that are stripped from table sugar when it’s refined and processed to get its white, powdery consistency. Coconut palm sugar is a relative newcomer, and not very common, but it contains higher amounts of magnesium, nitrogen, and Vitamin C than any other natural sweetener.

HoneyAgave Nectar is a health-food darling, best known for its very low glycemic index. In other words, it doesn’t cause as large of an insulin rush as other sweeteners. On the other hand, agave is also 90% fructose, which can cause serious problems for people who don’t digest fructose well. It also contains saponins, one of the same toxins that make grains and legumes so harmful. Although the lack of an insulin spike is tempting, agave is definitely the worst of the “all-natural” group: avoid it when you can.

Thus, although all of these natural sweeteners contain approximately as much sugar as the table sugar, some of them do at least give you a significant amount of nutrients along with the calories. This makes them preferable to the refined, chemically processed table sugar that most of us think of as “sugar.” Even though they aren’t healthy to consume to excess, honey, molasses, and maple syrup are superior to table sugar, and can make relatively harmless replacements in the occasional Paleo treat.

Table Sugar Substitutes: Artificial Sweeteners

Since all of these natural sweeteners do contain sugars, many people searching for a non-caloric sweetener turn to artificial compounds instead. The major types of artificial sweeteners are Aspartame (added to diet soft drinks or sold as Equal and NutraSweet), Saccharine (Sweet’n’Low), Stevia, and Sucralose (Splenda).

As with actual sugar, artificial sweeteners are hotly debated. Their main selling point is, of course, that they have no calories. As with the studies supposedly demonstrating the evils of salt, studies linking these sweeteners to cancer are not seriously concerning: they showed that rats who ate the equivalent of several hundred cans of soda every day did get a form of bladder cancer, but humans don’t even have the specific protein that causes this cancer, and nobody eats that much Splenda anyway. On the other hand, “no calories” doesn’t always translate into “no insulin response:” many types of zero-calorie sugar substitutes (with the exception of sugar alcohols, discussed below) may still contribute to metabolic problems and weight gain even though they don’t have any caloric value themselves. Essentially, when your body senses that you’ve eaten something sweet, it releases insulin, expecting to have some kind of carbohydrate (sugar) to digest. Even if you don’t follow up the sweet taste with any calories, the sudden rush of insulin can contribute to insulin resistance, and confusing your body like this can prompt you to overeat later.

Sugar alcohols are one type of artificial sweeteners that avoid this problem. These include xylitol, sorbitol, maltitol and erythritol (if it’s a sweetener that ends in –ol, it’s probably a sugar alcohol). These chemicals have a much lower glycemic index than sugar, because they’re very difficult for the body to digest. This isn’t necessarily a point in their favor, however: except for erythritol, sugar alcohols are polyols (the P in FODMAPs), meaning that they’re not the best choice for people with FODMAPs intolerance. Even people who don’t otherwise react to FODMAPs can have trouble with sugar alcohols: one study, for example, found that subjects who drank a xylitol-sweetened beverage reported higher rates of nausea, bloating, and other digestive troubles. Thus, sugar alcohols aren’t necessarily harmless for everyone, and if you react to them, they’re best avoided.

One noncaloric sugar substitute that gets slightly better press than the others is Stevia, an herbal extract frequently promoted as a natural alternative to products like Equal and Splenda. Although the raw leaves of the plant are also sweet, the “stevia” (sold under several brand names, including Truvia) that you can buy at the store as a liquid or a powder is a processed, refined version of those leaves. The scientific evidence on Stevia is just as self-contradictory as the evidence about sugar: some studies seem to demonstrate that Stevia does cause an insulin spike, and others suggest that it doesn’t. It may also have some beneficial effects on hypertension, memory, and blood lipids, but on the whole, the research doesn’t conclusively support one side or the other.

In short, artificial sweeteners are somewhat of a mixed bag, and more research is clearly needed on their effects before anyone can say with any certainty that they’re either harmful or harmless. If you do choose an artificial sweetener, erythritol seems to be one of the better choices – the jury is still out on chemicals like aspartame and sucralose, but sugar alcohols definitely don’t spike blood sugar, and erythritol is the sugar alcohol least likely to cause gastrointestinal problems and IBS-like symptoms. Stevia is another intriguing option that may be just as good – especially if you can get the whole leaves rather than the processed powder form. In general, while these substitutes won’t add anything nutritious to your diet, they probably won’t cause significant harm either, so consuming small amounts of them isn’t problematic for most people.

Conclusion: Dietary Recommendations for Sugar

Since the effects of sugar in the diet can vary so greatly depending on the source and composition of the specific sugar in question, the health of the person eating it, and the amount of sugar consumed, there is no one-size-fits-all recommendation. Not all people need to avoid sugar entirely. In many ways, it’s useful to think of a healthy sugar intake as falling on a spectrum: on one end of the scale is a very low-carbohydrate diet (meat and non-starchy vegetables) with as little sugar as physically possible. This kind of diet is perfect for diabetics and people with metabolic syndrome, people who react very poorly to starches and sugars in general, and some people trying to recover from an eating disorder.

A step above that would be a diet with some sugar-containing foods (fruit) but no added sweeteners. This more moderate approach is probably fine for healthy people who get regular exercise, especially if they don’t react poorly to fructose. Some people can even go further than that, and use small amounts of added sweeteners like honey, maple syrup, or even sugar itself without a problem. Serious athletes do need higher levels of carbohydrates than most other people, and even people who don’t enjoy endurance sports won’t see much harm from the occasional treat. Beyond this level, sugar consumption probably becomes unhealthy: eating large amounts of added sweeteners, especially processed chemical sweeteners like high-fructose corn syrup, isn’t good for anyone.

Ultimately, the most important consideration with sugar is your own reaction to it – and the only way to discover this is by experimenting. Try some Paleo chocolate pudding sweetened with a small amount of honey, or this meatloaf with a honey sauce and notice how you feel afterwards. Unless you’re diabetic or have another life-threatening metabolic disorder, there’s no need to be demonically strict about avoiding all sugar – and as we head into sugar season (the unholy trinity of Halloween, Thanksgiving, and Christmas), a sweet Paleo treat might even help banish cravings for candy corn, and chocolate Santas, helping you stay on track with your diet but keep your sanity intact.