by Shelly Guzman, RD, CD
I was recently contacted by a high school student who asked if I wouldn't mind answering some questions about sugar for a research paper he was writing. After answering the questions for the student, I thought "why not share them on the Momentum blog?" This is good info for everyone to know. So here they are...
Q: Could you describe for me the positive and negative effects sugar has the body?
A: Sugars are a natural part of fruits, vegetables, dairy products and grains. The carbohydrates in these foods provide energy, vitamins, minerals, fiber, and phytochemicals -- nutrients necessary for good health. Added sugars include table sugar, brown sugar, agave syrup, honey, molasses, maple syrup, and other caloric sweeteners and offer almost no nutritional value. They are found in soft drinks, candy, cakes, cookies, pies, fruit drinks/fruit-ades, dairy based desserts like ice cream or yogurt, and other grains like sweetened waffles or cereal. Naturally occurring and added sweeteners all fall under the category of “carbohydrates.”
There are no positive effects of added sugar per se, but sugar can be used to supply quick fuel to muscles during a moderate to hard endurance workout. You can significantly increase stamina by consuming about 30-60 g of carbohydrate per hour of exercise. However, a snack is not necessary if you exercise for less than one hour.
Exercise that lasts more than 60 minutes depletes carbohydrate from muscle glycogen stores, and you must increasingly rely on blood sugar for energy. Sugar, often from sports drinks, gels, or candy, helps to maintain a normal blood sugar level to keep the brain and muscles fed. Natural sugars from fruits and juices are also good choices for maintaining performance during exercise. Fueling with mixed carbohydrate sources during exercise can help you absorb more carbohydrate and have more available fuel.
The negative effects of added sugars is well-studied and continues to be a hot research topic. Sugar is linked to obesity, which is a risk factor for cardiovascular disease, type 2 diabetes, and certain cancers. Added sweeteners stimulate the body to release more insulin to process the sugar which may result in a low blood sugar level and feelings of hunger, fatigue, and craving for more sugar. Fructose (naturally found in fruit and honey) is concentrated in some sweeteners, like high fructose corn syrup and agave syrup, and has been linked to higher levels of triglycerides and bad cholesterol in the blood. The fructose from these sweeteners may also contribute to the unhealthy accumulation of deep abdominal fat. Another negative effect of added sugars is that they often displace the intake of more nutritious foods. The sugar highs and lows may cause people to continually make poor food choices. Sugars also create an acidic condition in the body, and in an effort to create balance, the body may draw alkalizing minerals from the bones and teeth -- leading to a link between sugar consumption and osteoporosis. Lastly, high sugar intake can contribute to tooth decay and cavities. Current recommendations suggest limiting refined sugar intake to no more than 6-10% of total daily calorie needs (Institute of Medicine) or about 6 teaspoons for women and 9 teaspoons for men per day (American Heart Association). For some perspective, a 12 ounce can of soda has 10 teaspoons of sugar! Most Americans consume almost 3 times the recommended limit for added sugar intake each day.
Q: What role does insulin play in the body, and why is it so important?
A: Your body has a system that regulates how much sugar is circulating in your blood stream. Insulin has many functions in the body, but one of it’s main roles is to regulate blood sugar levels in the blood. After you eat a meal, insulin transfers the excess sugar (remember, this includes all carbohydrates not just added sugars) in your blood to muscle, liver, and fat tissues where it is used as fuel or stored for later use. Simple carbohydrates, especially sugar, are quickly digested and enter the bloodstream rapidly. Insulin also acts quickly to clear the excess sugar from the bloodstream -- this accounts for the sugar high and subsequent sugar low that people often describe after eating sweets. Without insulin, sugar accumulates in the bloodstream (diabetes) leading to very serious health complications. Without insulin to act as the key, cells cannot access the energy that carbohydrates provide.
Q: Is it good to eat sugar right before a work out, or does it defeat the purpose of working out?
A: People often consume sweets for an “energy boost” before a workout. Depending on the caloric content of the sweet snack, you may not burn enough calories during the workout to make up for your pre-exercise splurge. However, exercise has benefits beyond burning calories which sugar intake should have little effect on including strength, speed, agility, flexibility, and endurance. In general though, having too much to eat before a workout without sufficient time for digestion, can affect performance. Most people can tolerate pre-exercise sugar intake without physical problems, but if you are sensitive to the highs and lows of sugar, eating a candy bar or drinking a soda before exercising can leave you feeling weak, shaky, and light-headed during your workout due to a rapid surge and subsequent drop in blood sugar. A better solution is to maintain a high energy level throughout the day by eating balanced meals (containing carbs, pro, and fat), and if necessary, having a carbohydrate rich snack like fruit or yogurt 30-60 minutes before exercise.
Q: How does sugar effect the liver?
A: Sugar, or glucose, is stored in the liver (and in muscles) as glycogen for later use. The liver can also produce glucose as needed. So you can think of the liver as a fuel reservoir. The need to store or release glucose is signaled by insulin and glucagon. All carbohydrate (from added sugars or naturally occurring sugars) is stored in the liver in the same manner.
Eating excess carbohydrates above your calorie needs over time leads to fat storage and weight gain. Because the liver and muscles can only store a certain amount of glycogen, excess glucose is stored as fat.