Nutrient Timing - The Future of Sports Nutrition

In the book Nutrient Timing, exercise physiologist John Ivy, Ph.D., and biochemist Robert Portman, Ph.D., argue that when athletes eat is as important as what they eat. Citing dozens of recent studies, they make a solid case.

Although Nutrient Timing is aimed primarily at an audience of strength athletes, there is a lot of information in the book that is valuable to endurance athletes as well.

Most endurance athletes are aware that it's beneficial to drink a carbohydrate sports drink during exercise. But according to the authors of Nutrient Timing, there are many other beneficial ways to use nutrition during and after exercise that most endurance athletes don't know about.

Here are five of them:

1. Consuming protein with carbohydrate during exercise can increase endurance

It appears that the effectiveness of carbohydrate consumption during exercise is limited by the maximum rate at which the liver can release glucose into the bloodstream -- about 1 gram per minute. It's not hard to consume enough carbohydrate in a sports drink to reach this limit, and consuming any more will not help.

But the muscles can also use protein for energy. A supplement combining carbohydrate and protein can therefore provide more energy and delay fatigue by allowing the muscles to conserve more glycogen (their main energy source).

A study at the University of Texas compared the effects of a carbohydrate and a carbohydrate-protein supplement on endurance performance. Trained cyclists last 36% longer in a ride to exhaustion when fed the carbohydrate-protein drink than when fed the carbohydrate drink.

2. Consuming protein during exercise can reduce muscle damage

When protein is not consumed during exercise, muscle proteins are broken down for energy, resulting in muscle damage. When protein is consumed during exercise, such damage is minimized.

This was demonstrated in a study done at James Madison University. Researchers fed either a regular carbohydrate sports drink or a carbohydrate-protein drink to subjects during a hard stationary bike ride and measured post-exercise levels of creatine phosphokinase (CPK) in the blood. CPK is a biomarker of muscle damage.

The subjects receiving the carbohydrate/protein supplement had CPK levels 83% lower than those receiving the carbohydrate supplement, indicating significantly less muscle damage during exercise.

3. The sooner you consume nutrients after exercise, the more effective they are

The muscle cells are especially insulin-sensitive for the first 45 minutes after exercise is completed. Insulin transports glucose and amino acids into the muscle cells and stimulates muscle protein and glycogen synthesis. Consuming carbohydrate and protein within this 45-minute window will therefore stimulate the muscle-recovery processes much more powerfully than consuming the same nutrients later.

In a study at Vanderbilt University, researchers looked at the effect of a carbohydrate-protein supplement on protein synthesis following a 60-minute bout of exercise. Subjects were given the supplement immediately after exercise or three hours later. Protein synthesis was almost three times higher when the supplement was given immediately after the workout. Other studies have shown a similar pattern with respect to muscle glycogen replenishment.

4. Post-exercise nutrition reduces injuries and sickness

In a remarkable new study, Marine recruits representing six platoons were assigned to one of three treatment protocols during 54 days of basic training. Each day after exercise, some Marines received a carbohydrate drink, others a carbohydrate-protein drink, and still others flavored water.

The investigators reported that the protein-supplemented group had an average of 33% fewer total medical visits, 28% fewer visits due to bacterial/viral infections, 37% fewer visits due to muscle/joint problems, and 83% fewer visits due to heat exhaustion compared to members of the other groups. They also had less muscle soreness.

This new evidence indicates that athletes in heavy training will stay healthier if they consume a carbohydrate-protein supplement immediately following each workout. Strenuous exercise suppresses the immune system, opening the door to infections. Carbohydrate and the amino acid glutamine fuel the immune system and counteract this suppression.

5. Post-exercise nutrition improves performance in the next workout

It stands to reason that if immediate supplementation after exercise results in a faster, stronger recovery, it could also improve performance in the next workout. The James Madison University study cited above showed this to be the case.

After completing a performance ride on day one, the subjects of this study were asked to come back after a 15-hour recovery period. Upon returning, the subjects performed a ride to exhaustion at 85% of their VO2max. Subjects receiving the carbohydrate/protein drink during the initial performance ride the day before were able to ride almost 40% longer than those receiving the carbohydrate drink during the prior exercise.

Summary

The science of sports nutrition has come a long way since the first sports drinks were formulated back in the '60s. It's time to bring your sports nutrition practice into the 21st century. Nutrient Timing offers a compelling theory on recovery nutrition, with a growing body of scientific evidence to support it.