Table sugar is sucrose which breaks down into glucose and fructose in the body.
As I have mentioned previously on this site, the war on fat has been discontinued and replaced with a war on carbs, specifically sugar. Added sugar appears to be the big problem. One perspective considers added sugar to be addictive and toxic but natural sugar to be fine. Advocates of this point of view tend to blame processed foods exclusively for too much sugar in the American diet. The more conventional perspective is that sugar adds unnecessary calories to the diet contributing to obesity1. Added sugar when consumed in excessive amounts in a moderate-calorie diet crowds out important nutrients.
Sucrose. The discussion on sugar has become more sophisticated in recent years. When I was growing up, the focus was on table sugar or sucrose. Many of us are old enough to remember the ubiquitous glass containers on the tables of restaurant booths containing white granules that did not always flow so well unless there were rice grains at the bottom. Now we find small, white packets containing a teaspoon of sucrose. A molecule of sucrose is rapidly broken down into a molecule of glucose and a molecule of fructose. Cane sugar on a food label generally refers to sucrose, but it is frequently converted to syrup which means that it has been broken down into glucose and fructose using enzymes.
Glucose. Glucose is the type of sugar that flows in our blood. Glucose is essential for proper brain function. When we consume a meal containing sugars or starch the level of glucose in the blood rises. Insulin is the hormone that lowers the level of glucose. Diabetics cannot produce enough insulin rapidly enough to adequately respond to a surge of glucose. Consistently high levels of the sugar in the blood can lead to long-term damage over time in many parts of the body, particularly the eyes and feet. Once insulin does kick in for a diabetic, however, the level of glucose crashes. Dangerously low levels of glucose in the blood can lead to a light head and even death. The glycemic index is used to tell us which carbs are more likely to break down rapidly. White bread and baked potatoes are notorious for a high glycemic index. Add butter and sour cream to a baked potato, however, and the index comes down as the fat added potato slows down digestion of the potato and thus release of glucose. In addition to fat, fiber slows digestion which is why whole fruits like apples and oranges have a low glycemic index but their juices, particularly if the fiber has been removed do not.
Fructose. Lately, food pundits have become concerned about fructose, particularly high fructose corn syrup. Fructose has a low glycemic index, but that does not mean that it is harmless. Large amounts of fructose are metabolized in the liver and contribute to non-alcoholic liver disease. Most research suggests that when a reasonably equal amount of fructose and glucose are released at the same time, the fructose is not considered a problem in liver disease2. Corn syrup is almost exclusively glucose, but again the use of enzymes can convert a little over half of that glucose to fructose. The amount of fructose in high fructose corn syrup is about 54% and probably has little effect on liver disease. An alternative, natural sweetener, agave syrup, contains over 80% fructose and thus much more likely to cause liver problems than high fructose corn syrup.
Alternatives. In a search for new sweeteners to satisfy America’s sweet tooth, a new ingredient is finding its way into healthy recipes and onto package labels—rice syrup or brown rice syrup. Big Food loves this sweetener as its name does not sound like a chemical or even a sugar. Thus, its presence helps produce a cleaner label. Brown rice syrup also has a reputation of not spiking blood-glucose levels and is being used to replace artificial sweeteners. A major sugar in brown rice syrup, however, is maltose which is conveniently broken down in the body into two molecules of glucose. Commercial production of brown rice syrup can involve the use of enzymes to break down the starch into maltose making it no less processed or natural than cane syrup or high fructose corn syrup. The glycemic index for maltose and for brown rice syrup is higher than for sucrose. Brown rice syrup, then, is likely to be more harmful to diabetics than table sugar. That has not stopped Big Food from using it in their products. It is rapidly becoming a major ingredient in processed food.
Sugar added at home. If I had any doubt that America has a sugar problem I was disabused of that notion at holiday parties I enjoyed earlier this month. I observed friends and relatives down large amounts of home-baked cookies. The major sugar added in the home is sucrose. Two of these cookies likely exceed the daily limit of 6 teaspoons recommended by American Heart Association. Four cookies probably top the more modest limits of the Dietary Guidelines which allow 12 teaspoons a day. These numbers assume that the cookie eaters don’t put any tablespoons of sugar, a packet at a time, in their coffee. Most of the cookie eaters I noticed were eating at least a dozen in a sitting. Fortunately, these cookies probably have a low glycemic index because of all the butter or other sources of fat in them. Then again, a Snickers bar has a low index value as well for the same reason.
Bottom line. Almost all Americans agree that we have a sugar problem. The warning that any type of sugar in any amount, except when consumed in fresh fruits and vegetables, damages health is not well founded. The idea that many of us should be watching our sugar intake more carefully is warranted. Most of us do not realize the severity of the latest guidelines. I think that the 6-teaspoon limit is extreme, but the 12-teaspoon guideline, while still restrictive, is reasonable. Dedicated readers might want to make an estimate of how many teaspoons of added sugar a day that they consume in processed, restaurant and homemade foods each day. It might be a big surprise. Getting some enjoyment out of life by eating sweets is a good thing. By limiting those sweets it may make those we do eat even more special. Three recent scientific reviews of numerous individual studies suggest that moderate consumption of sugars pose little health risk. However, these reviews suggest that people with lower glycemic diets have a modestly lower risk of breast cancer3, diabetes4 and obesity5 over their lifetime than those who do not watch their sugar consumption as carefully.
Next week: Artificial sweeteners
1 Khan, T.A. and J.L. Sievenpiper, 2016. Controversies about sugars: results from systematic reviews and meta-analyses on obesity, cardiometabolic disease and diabetes. European Journal of Nutrition 55(Supplement 2):S25-S43.
2 Rippe, J.M. and T.J. Angelopoulos, 2016. Sugars, obesity , and cardiovascular disease: results from recent randomized control trials. European Journal of Nutrition 55(Supplement 2):S45-S53.
3 Mullie, P., A. Koechlin, M. Bonoi, P. Autier and P. Boyle, 2016. Relation between breast cancer and high glycemic index of glycemic load: A meta-analysis of prospective cohort studies. Critical Reviews in Food Science and Nutrition 56:152-159.
4 Schwingshackl, L. and G. Hoffmann, 2013. Long-term effects of low glycemic index/load vs. high glycemic index/load diets on parameters of obesity and obesity-associated risks: A systematic review and meta-analysis. Nutrition, Metabolism & Cardiovascular Diseases 23:699-706.
5 Greenwood,D.C., D.E. Threapleton, C.E.L. Evans, C.L. Cleghorn, C. Nykjaer, C. Woodhead and V.J. Burley, 2013. Glycemic index, glycemic load, carbohydrates, and type 2 diabetes: Systematic review and dose-response meta-analysis of prospective studies. Diabetes Care 36:4166-4171.