Sugar: What endurance athletes need to know about it

"I read an article published in The British Journal of Medicine that sugar causes heart disease. What would you suggest for an energy drink?" - male triathlete, via e-mail

Confused about sugar? You're not alone. Sugar - or to be more specific, high fructose corn syrup - has become a target of the popular press as a primary cause of obesity, diabetes, and high blood pressure.

"I have always had good luck with 24-hour high glycemic carbohydrate loading before a marathon, but I'm wondering if I should continue doing this. My fasting blood sugar was 115 (high). I am not overweight."

As a sports dietitian who studies peer reviewed journals on a regular basis and a serious master's level competitor, I know the boost from an energy gel can make all the difference in the final 10K of a marathon race. On the other hand, my own preference for sweet treats can be a problem. Like right now, for example. As I write this column, my sweet tooth urges me to take a break and head to the kitchen for a chocolate chip cookie. After all, how bad can one homemade, 100 percent organic cookie be?

Fructose: Is that what's for dinner?

Barry M. Popkin, Ph.D., a researcher in the Department of Nutrition at the University of North Carolina, Chapel Hill, did ask what America was having for dinner. And for all the other "eating occasions" (which average about every three hours in the U.S.). Then he wrote a summary of his research for The American Journal of Clinical Nutrition, 2008.

Data from his analysis of all added sugars, primarily sucrose (table sugar) and HFCS, showed that consumption in the U.S. has increased steadily since 1970. Although during this time period HFCS replaced 50 percent of the sucrose used as a sweetener in foods, Popkin told me via e-mail, "We challenged the research field to study the topic (of fructose metabolism) and found that HFCS acts like all other sugars. There is no difference for HFCS or any other sugar. They all contain about half fructose and that fructose has the same adverse effects on health."

Other researchers agree with Popkin. Whether our soda has sugar or HFCS, we are ingesting about a 50/50 mix of glucose and fructose.

The next question I raised with Popkin concerned the affect on athletes from sugar consumption. "For athletes, fructose in sugar or HFCS is equally bad, as all are sugars," he replied.

Excessive sugar vs. safe intake

History is a great teacher, and if we look back, the taste of sugar has always been attractive to humans. Prior to the 18th century, sugar was scarce and intake was limited to natural sources. Berries and honey provided a small amount of glucose and fructose. Following the Crusades, intercontinental trade routes opened up to Europe, making sugar more available. Then the technology to extract and refine sugar was developed, and baked goods and teas with sugar rapidly became popular. Between the 18th and 19th century in England, sugar consumption grew by a whopping 1,500 percent.

Sucrose (table sugar) was the main sweetener used throughout the world and U.S. until the 1960s when the technology to create HFCS was developed and its popularity rose with The Beatles. Food manufacturers shifted to the use of HFCS because it was cheaper, kept foods moist and allowed for a longer shelf life for products. Gone were day-old bakery sales and Twinkies? lasted forever.

I have always joked that the only reason I eat red meat is so that I can use catsup. Beef, like all natural meats, is virtually devoid of sugar. To my taste buds, a heavy dose of tomato, salt and sugar will improve any hamburger. In one tablespoon of catsup, there are 4 grams (1 teaspoon) of added sugar. My sugar preference is almost universal. Consider the popularity of pizza, cold cuts, ready-to-eat cereals and sport bars in which HFCS is added to entice hungry consumers. It is not about nutrition. Sugar sells.

Between 1959 and 2000, the USDA Economic Research Service's data indicates the per capita consumption of caloric sweeteners - mainly sucrose (table sugar) and HFCS - increased by 39 percent. In 2000, each American consumed an average of 32 teaspoons of sugar per day. Much of the additional sugar was in the form of processed refined grains, sweet teas and soda.

But before we blame our sweet tooth for all that extra belly fat, keep in mind that between 1997 and 2000 per capita consumption of added fats also jumped 17 percent, from 64 pounds per person to 74.5 pounds.

Regarding the health risk of HFCS over sucrose, after careful review of human studies to date, researcher L. Tappy, Ph.D., of the Department of Physiology at the University of Lausanne, Switzerland, concluded, "At present not the single hint of HFCS may have more deleterious effect on body weight than other sources of sugar. Regarding the relationship between fructose or sucrose intake and cardiovascular risk factors or type 2 diabetes, the evidence is even sparser."

The often overlooked fact, according to Tappy, was the fact that added sugars were often consumed with added fats, leading to calorie excess.

For endurance athletes, how much is too much?

Although recent studies have absolved HFCS from being the bad guy in terms of our health, there is no question that an excessive amount of fructose in the diet is not good. Some of the negative effects of high fructose intake include high blood pressure, decreased insulin sensitivity, increased risk of gout, heart disease and fat gain. The exact amount associated with health risk for each individual is dependent on genetics and activity level.

On average, daily intake of fructose in the U.S. is about 50 grams per day. Consuming more than 100 grams of fructose daily will increase triglyceride levels. If eating within the guidelines of a healthy diet (see sidebar) and avoiding refined grain products, desserts, snacks and beverages with added sugars, natural fructose in the diet is quite low.

However, semi-prepared foods, restaurant fare and snacks can rack up added sugar grams past the American Heart Association (AHA) guidelines for added sugar which are: for men, less than 36 grams or about 150 calories; and for women, 20 grams or 100 calories.

For example, although Subway? restaurants offer low fat, low sugar choices such as fresh vegetables, low fat meat and 9-grain buns, the unsavvy consumer can put together a high sugar combination. A 6-inch chicken teriyaki sub paired with a small Fruizle Express comes to 50 grams of sugar. Like many condiments, sweet and sour teriyaki sauce is loaded with sugar, and the healthy sounding fruit drink is worth about three fruit servings, enough for a whole day.

Every day diet vs. race day

That sport drinks and energy gels can improve sprint performance at the end of marathon events and aid in maintaining blood sugar during exercise has been proven. The possible harmful effects of fructose associated with excess intake must be weighed against the benefits of including it in sport nutrition products.

Studies show that working muscles are able to absorb and metabolize a blend of glucose and fructose as much as 40 percent faster than pure glucose alone, which is critical when exercise is performed at high intensity level and energy need is greatest. This difference in metabolism is attributed to the different sugar transporters that are used for intestinal absorption, as well as their differences in metabolic processes. Glucose is primarily metabolized by the exercising muscle, whereas fructose must first go through the liver. Fructose absorption through the intestine is limited by transporter proteins, and in at least 50 percent of the population this limitation can cause significant gastrointestinal distress, particularly during exercise.

A second benefit to including fructose in sport beverages is to maintain psychological effort during exercise. As any serious competitor can attest, the ability to maintain pace and effort when muscles are telling you otherwise cannot be overrated. Recent studies of cyclists have shown that athletes reported a reduction in perception of fatigue and their performance times improved when using a beverage supplement that consisted of a fructose/glucose blend vs. a glucose only drink.

When athletes have a high total caloric need, as in the Tour de France for example, it is difficult for them to meet and replace glycogen stores without using liquid sport drinks with glucose and fructose blends. In addition, the intensity of exercise decreases appetite. Most ultraendurance athletes depend on savory snacks, such as baked goods and pastries, to boost calorie intake.

Taste, benefits & a healthy perspective

Simple sugars are plentiful in our modern day food supply, and there are a number of names for essentially the same chemical structure of glucose or fructose. So whether my sport bar is made with organic brown rice syrup, molasses, cane sugar, maltodextrin, agave syrup, honey or high fructose corn syrup, it pretty much comes down to being aware that sweet taste is going to metabolically be quite similar.

Does my intake match my energy need? As Mary Poppins sang, "Just a spoonful of sugar makes the medicine go down." We like it, but a little goes a long way. One chocolate chip cookie? That's probably A.O.K.

A low sugar added menu:

Total calories: 2,400, total carbohydrate: 276 g, sugar 73 g, protein 131 g, sodium 2,858 mg

Breakfast

Quaker regular instant oatmeal, 2 packets

English walnuts, 1 Tbsp

1 small navel orange

1 slice whole wheat bread (1 oz)

1/2 tsp of Take Control margarine

Snack

One small, fresh apple

Lunch

Subway turkey & ham sandwich, no oil

One small apple

Low calorie beverage

Snack

Rye Krisp crackers, 3 each

1 individually wrappped stick of mozzarella cheese

Dinner

Chicken breast, 6 oz grilled or roasted, no skin

Large baked potato

1 Tbsp Take Control margarine

1 cup green beans

2 cups mixed green salad with 2 Tbsp Italian dressing

Snack

Apple, 1 small

Sample high sugar menu

Total calories: 2753, fat: 83 g, carbs: 409 g, sugar: 205 g, sodium: 4,800 mg

Breakfast

1 large low fat, banana nut Dunkin Donuts muffin

1 Starbucks Frapuccino coffee

8 oz orange juice

Lunch

Chick-A-Fil chicken caesar wrap

Snack

16 oz Gatorade

Dinner

2 pcs. lasagna dinner

1 slice Italian bread

1 cup mixed salad greens

1 T Italian dressing

Snack

2 Muskateer's bar

1 package original flavor Sun Chips

1 Nutrigrain bar

A fast food lunch

Total calories: 701, carbs: 93 g, sugar: 60 g, total fat: 24 g

1 double hamburger at Burger King

2 tbsp catsup

12 oz soda (sweetened)

Donna Marlor, MA, RD, CSSD, is a registered dietician who specializes in nutrition for endurance exercise and weight management. She offers motivational coaching and behavioral skills training to change eating patterns. Marlor is a consultant to the U.S. Olympic Education Center in Marquette, Michigan, and works with many individual athletes from novice to elite. A former collegiate alpine and cross-country skier, Marlor still enjoys Master's level competition as a skier and runner as well as spending time with her family and chocolate lab in the Upper Peninsula. She can be reached via www.DonnaMarlor.com or at 906/360-9049.