Exercise Fueling, Beets, Gut Bacteria, Your Heart and More

author : Nancy Clark

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Nutrition highlights from The American College of Sports Medicine 2013.

By Nancy Clark MS RD CSSD

2013 Sports Nutrition Update from ACSM

The American College of Sports Medicine (www.ACSM.org) is the world's largest organization of sports medicine and exercise science professionals. At ACSM's annual meeting in Indianapolis (May, 2013), over 6,000 exercise scientists, sports dietitians, physicians, and health professionals gathered to share their research. Here are a few nutrition highlights.

• For fuel during endurance exercise, the recommended intake is 30 grams of carbohydrate per hour during 1 to 2 hours of exercise; 60-90 g carb/h for exercise lasting more than 2.5 hours. Yet, some athletes have intestinal issues and prefer to abstain from food and fluids before and during exercise. If you train on “empty,” you should know that just rinsing your mouth with a sports drink can reduce the perception of fatigue and improve performance by 3%. The next time your stomach can’t handle anything and you are about to hit the wall, try swishing and spitting?

• Strength and power athletes who do high intensity exercise (i.e., gymnastics, weight lifting, ice hockey) rely on carbohydrates for fuel. These strength/power athletes commonly eat plenty of protein but they often fail to consume adequate carbohydrates. They may look towards supplements to enhance their energy when more oatmeal, sweet potato, or brown rice could do the job.

Some popular sports supplements among strength/power athletes include creatine (for weight lifting and other repetitive high intensity exercise that lasts for less than 30 seconds) and beta-alanine and sodium bicarbonate (buffers that reduce fatigue associated with lactic acid build-up during 1 to 6 minutes of sprint-type exercise, including track and crew). Sodium bicarbonate is best tolerated when taken in capsule-form, not as baking soda.

Strength/power athletes who train intensely should be sure to drink enough water. Being dehydrated by 3% reduces muscle power and strength in the upper body by 7% and in the lower body by 19%. Don't underestimate the power of proper hydration!

• Could eating beets/drinking beet juice before daily training help athletes train harder and thereby compete better? Perhaps. Nitrate-rich beets, concentrate beetroot juice “shots”, and other nitrate-rich foods (spinach, rhubarb, arugula) get converted into nitric oxide, which helps reduce the amount of oxygen needed during constant-work-rate exercise. Hence, for the same oxygen uptake, athletes who consume beet juice “shots” might be able to exercise harder. For example, a runner might improve by 5 seconds a mile. 

Some athletes respond better to dietary nitrates than others. Perhaps the “strong responders” routinely eat very few fruits and veggies, hence have a low nitric oxide baseline. Consuming nitrates might contribute to a more dramatic response? Note: bacteria in the mouth help convert dietary nitrate into nitric oxide. Skip the mouthwash!

• Bacteria and other microbes might be very influential regarding good health. The human body contains 10 times more microbial cells than human cells. About 2 to 6 pounds of these microbes live in the intestines, where they help digest food, synthesize vitamins, and enhance the immune system. This gut ecosystem changes according to diet, use of antibiotics, heat stroke, and other factors (some known, some unknown). For example, the gut bacteria of obese children can differ from that of lean kids, just as the gut bacteria of gastric bypass clients can change after surgery. (Maybe this is one reason why bypass patients lose weight faster than predicted?)

Microbes might play also play a role in Alzheimer's disease, hyperactivity in kids, and heart disease, so take good care of your gut! This means enjoying fiber-rich fruits, vegetables, and whole grains (microbes like to eat fiber) as well as cultured foods (yogurt, kefir) and fermented foods (miso, Kimchi, tempeh, blue cheese). Probiotic supplements might also be helpful.

For female athletes with PMS, taking probiotics for the seven days before the start of the menstrual period might reduce PMS symptoms, as well as the risk of diarrhea (a common problem at the time of the menstrual period).

• Regular exercise 4 to 5 days a week helps maintain a “youthful” heart. Yet, the performance of even master athletes declines with age. Champion runners might lose about 0.5% of their VO₂-max per year even if they train vigorously. Fit older men (ages 50-70) tend to lose about 1.5% per year.

• Among untrained women ages 60 to 74, exercising 2 days a week was more beneficial than 3 days a week. When women exercised 3 days a week, they became tired and did fewer other activities. Don’t push your relatives too hard!

•Mortality increases during heat waves. The 2003 European heat wave contributed to 14,000 more deaths than usual, with more than 90% of those deaths in people older than 65 years. The deadliest impact is seen in people over 74 years. Most of the deaths are due to cardiovascular problems; the heart has to pump double the normal amount of blood to get it to the extremities where is can dissipate body heat. If global warming means we will be dealing with very hot weather, we certainly want to stay fit as we age.

• Every 34 seconds someone in the US has a heart attack. Eighty percent of first heart attacks can be predicted by 5 risk factors: smoking, high triglycerides, high blood pressure, diabetes, and obesity. Both endurance and resistance exercise help protect the heart. Just 3 to 5 days of training can offer health-protective benefits that last for 9 to 18 days. Encourage your unfit friends and relatives to get moving.

• Are athletes at high risk for developing osteoarthritis? No clear evidence indicates exercise is associated with arthritis. Clear risk factors include age, sex (more women than men get arthritis), genetics, obesity (three times higher risk), and osteoporosis. Strength training seems to be protective.

• Sleep deprivation is associated with obesity.  In the past 20 years, Americans have been sleeping less. This drop in sleep mirrors a rise in obesity. Sleep is restorative; the body needs sleep to maintain normal circadian rhythms. Good night.

Nancy Clark MS RD CSSD (Board Certified Specialist in Sports Dietetics) counsels both fitness exercisers and competitive athletes in her private practice in the Boston-area (617-795-1875). Her Sports Nutrition Guidebook, Food Guide for Marathoners and Cyclist's Food Guide all offer helpful information. The books are available via www.nancyclarkrd.com. See also www.sportsnutritionworkshop.com.

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date: August 5, 2013