Running Delight
Runners Need Fat in their Diet
Published June 7, 1999 in The Post-Standard.By Dr Kamal Jabbour, Contributing Writer
Finally, there is medical confirmation of what runners around the world have known all along, that eating fatty foods is good for them. In fact, a study at the University of Buffalo shows that runners who limit their fat intake compromise their immune system and increase their risks of infections and disease.
In findings presented on May 22, 1999 at the fourth International Society for Exercise and Immunology Symposium in Rome, Italy, University of Buffalo researchers reported that running 40 miles per week on a diet consisting of only 17 percent fat compromised a runner's immune system.
Medium and high-fat diets, where 32 and 41 percent of the calories came from fat, enhanced the immune system's ability to withstand the rigors of intense training. Professor Jaya Venkatraman, the lead researcher on the study, suggested that higher-fat diets lowered pro-inflammatory cytokines and increased anti-inflammatory cytokines. In addition, fat intake affected the release of free radicals and hormones, in turn impacting the immune system's ability to fight disease.
Conventional wisdom in the sports nutrition community had long promoted a low-fat, high-carbohydrate diet for improved health and increased performance. However, many endurance athletes defied these rules by indulging their cravings for high-calorie, high-fat foods.
Earlier studies published by the University of Buffalo researchers confirmed that competitive runners who increased the proportion of fat in their diets improved their endurance without any adverse effects on their weight, body composition, blood pressure, heart rate or cholesterol.
While moderate levels of exercise enhanced the immune system, high-intensity and endurance exercise produced excessive levels of free radicals, thereby stressing the immune system. Since a high level of fat was initially thought to weaken the immune system, the researchers worried that improved performance could only be achieved at the cost of reduced immunity to disease. Hence, their recent research sought to determine whether increasing dietary fat intake would indeed improve performance while compromising the immune system.
The Buffalo study included six female and eight male competitive runners who trained at 40 miles a week. These runners were part of a larger performance study on the impact of dietary fat on performance and nutritional status. The runners followed their normal diets for one month, followed by one month each on a diet composed of 17 percent, 32 percent and 41 percent fat. Protein intake remained constant at 15 percent throughout the study, while carbohydrates made up the balance.
At the end of each month, the immunity of the runners was estimated by measuring the concentrations of white blood cells, cytokines and plasma cortisol in blood samples taken before and after endurance exercise. Results showed that natural killer cells, among the body's defense mechanisms to fight infection, more than doubled in runners after the high-fat diet, compared to the low-fat regimen. In addition, the levels of inflammation-causing prostaglandins increased after the endurance exercise, and were higher when the runners were on the low-fat diet.
The study confirmed that athletes not only performed better on a higher-fat diet than on a low-fat diet, but that their immune system was further enhanced on the high-fat diet. These findings should not surprise the myriad of marathon runners who have fought colds and infections to run a marathon. In fact, a recent survey showed that over one half of the finishers in the New York City Marathon reported getting sick within a month of running the marathon.
Although the Buffalo study concluded in favor of runners cravings for pizza and ice cream, it seemed to neglect the all-too-important psychological component. A total stranger to distance running, my grandmother firmly believed that a well-fed body was best equipped to succeed in physical as well as mental endeavours. Her lasting impact on us is evident in our rapidly increasing waistlines and race times.
Kamal Jabbour's diet extends the range of the Buffalo study towards higher immunity and stronger endurance. His RUNNING Column appears in The Post-Standard on Mondays. He maintains The Syracuse Running Page and receives email at jabbour@syr.edu.