In a recent New York Times piece, Gretchen Reynolds examines the impact sweeteners like fructose and sucrose have on active versus inactive people.
Reynolds cites a body of new evidence that suggests people who regularly work out need not be particularly concerned with ingesting large amounts of fructose and other sugars, and in certain circumstances, Reynolds claims these various forms of sugars may even be beneficial to the highly active.
Reynolds focuses on one new study recently published in Medicine & Science in Sports & Exercise, involving a group of highly trained cyclists and their livers. Researchers instructed cyclists to ride to exhaustion on several different occasions. After each ride, they drank beverages sweetened with fructose or glucose, and some also drank a milk-sugar sweetener.
To better understand the results of the research, Reynolds explains that the liver stores glycogen, the body’s form of glucose. All sugars, including sucrose, or table sugar, and high-fructose corn syrup, are converted into glucose, and stored as glycogen in the body. Strenuous exercise diminishes or exhausts this liver glycogen, and until those stores are replenished, the body isn’t fully ready for another exercise bout.
In the study, says Reynolds, the scientists used magnetic resonance imaging to measure the size of each rider’s liver, before and after the rides.
“All of the cyclists lost liver volume during their workouts, a sign their livers were depleted of glycogen. But those who afterward drank fructose replaced the lost volume rapidly…The researchers concluded that fructose-sweetened drinks were twice as effective as the glucose-sweetened drinks in stimulating the liver to recover.”
Reynolds notes that absorption was best if the sweetener contained both glucose and fructose, citing a 2008 study supporting the claim.
Reynolds warns that the freewheeling ingestion of larger amounts of sugar are recommended only for the “serious athlete” who works out for more than two hours at a time.
However, Reynolds notes that Dr. Richard J. Johnson, a professor of medicine at the University of Colorado in Denver, says activity (moderate exercise) can “significantly reduce the health risks associated with fructose and other forms of sugar.” Johnson, who has long studied fructose metabolism was an author of a review article last year about fructose and exercise.
According to a comprehensive review published in The Journal of the American Medical Association, moderate exercise also aids in the control of blood sugar levels if a person has developed Type 2 diabetes.
Over all, said Dr. Johnson, “the current science suggests that exercise exerts a positive physiological influence” on some of the same metabolic pathways that sugar harms. “Exercise may make you resistant to the undesirable effects of sugar,” he said.
It’s easy to become confused and misled with the terms glucose, fructose, dextrose, sucrose, and high-fructose corn syrup, since many times some of these terms are erroneously used interchangeably, adding even more confusion to the mix.
In very simple terms, there are essentially three main types of sugar:
1) Glucose is one of the main products of photosynthesis which occurs widely in most plant and animal tissue. But glucose is manufactured by the body when starches and carbohydrates — pasta, grain, potatoes — are broken down; blood transports glucose to cells for use as energy.
2) Fructose is a sugar found naturally in fruits.
3) Sucrose is table sugar which primarily comes from sugar cane and sugar beets.
All other terms are basically variations or different forms of the three terms listed above.
Dextrose is glucose in its active form, and is found in both plant and animal tissue. Dextrose is an “isomer” of glucose that is found in honey. Bees modify honey which forms levulose, dextrose, and sucrose.
Corn syrup is made from the starch of maize. High fructose corn syrup consists of a group of corn syrups that has undergone enzymatic processing to convert some of its glucose into fructose.
Let’s consider the following statement from Reynolds’ piece:
“In sedentary people, ingesting large amounts of fructose, which is mostly metabolized in the liver, has been associated with the development of a disorder known as fatty liver. That condition can reduce the body’s ability to respond to insulin, the hormone that helps to control blood sugar. A person with a fatty liver often develops resistance to insulin, becomes less able to control levels of glucose in the blood, and drifts almost inexorably toward Type 2 diabetes.”
Reynolds’ use of the word “fructose” in the above statement can be somewhat misleading since fructose “releases its energy slower than glucose, and does not need insulin to be metabolized, and therefore is a marginally better choice for diabetics”.
Glucose, on the other hand, travels to the liver where it is regulated and broken down by insulin. Glucose needs insulin for proper metabolizing while fructose does not. When blood glucose levels aren’t properly regulated, one can develop diabetes.
The term hyperglycemia is used when there are extremely high glucose levels due to too much sugar or too little insulin. Hypoglycemia is the result of abnormally low blood sugar, resulting from excessive insulin or a poor diet.
The more refined the sugar, like sucrose (table sugar), the worse it is for your overall health. William Dufty, author of Sugar Blues, claims that the consumption of refined sugar is the number one cause of diabetes, and argues that refined sugar is an addictive drug, comparing sugar to opium, morphine, and heroin.