LC Health: Nutrition and Marathon Training


Nutrition and Marathon Training

-Written by Stephanie Nunes, RD

There is much confusion on the health effects of caffeine. I am going to address specific topics that may be of interest to athletes: Dehydration, Bone Health, Sports Performance, Cancer, and Heart Disease.

Extensive research has been conducted on the health effects and safety of caffeine consumption and the general consensus appears to be that moderate caffeine consumption (approximately 300mg/day) is safe. It is estimated that the average daily caffeine consumption among Americans is 280mg/day.

A Few Common Sources of Caffeine

Source Caffeine
8 oz Brewed Coffee 135 mg
1 oz Espresso 30-50 mg
8 oz Green Tea 25-40 mg
8 oz Black Tea 40-70 mg
12 oz Coca-Cola 34.5 mg
12 oz Diet Coke 46.5 mg
12 oz Mountain Dew 55.5 mg
SoBe No Fear 158 mg
1.45 oz Sweet chocolate bar 27 mg
Exedrin 65 mg


Researchers used to believe that caffeinated beverages had a diuretic effect and caused dehydration. Recent research now shows that coffee, tea, and other caffeine-containing beverages do not affect hydration status on those who are already accustomed to consuming caffeine. Caffeine only has a diuretic effect if you consume large amounts of it (500-600 mg/day).

My advice: Enjoy your favorite caffeinated beverage while continuing to focus on maintaining proper hydration with fluids such as water, juices, sports drinks, etc.

Bone Health

Research has shown that caffeine is not a significant risk factor for poor bone health when adequate calcium is consumed.

My Advice: Include at least 2 servings of calcium rich foods daily and add milk to your coffee or tea (my favorite is a non-fat mocha!)

Sports Performance

Early researchers thought caffeine's benefit on sports performance was linked to its ability to spare muscle glycogen and increase fatty acid metabolism. Now the current thinking is that the positive effects of caffeine have more to do with "mental energy". Studies on sports performance have shown that caffeine had a 24% improvement in endurance performance and 4% improvement in strength performance. The quantity used which showed the biggest improvement was 6 mg/kg body weight. Less than 3 mg/kg showed a smaller improvement or no improvement at all. It is also thought by some that the amount of caffeine needed for sports performance depends partly on "caffeine sensitivity".

Additional Note: Substances in coffee and tea can interfere with iron absorption.

My Advice: If you suffer from anemia, do not drink tea or coffee with your meals or within one hour after. The best advice would be to drink them an hour before eating. If you don't usually use caffeine but want to try it for sports performance, watch for stomach distress.


The American Institute for Cancer Research (AICR) recently released an article, "The Truth about Caffeine and Cancer". The AICR stated that coffee is no longer associated with increased cancer risk. In fact, "because it contains antioxidants and anti-inflammatory compounds, coffee may actually boost health and possibly reduce cancer risk." Tea continues to show cancer combating benefits, especially green tea.

Heart Disease

Recent research has shown no relationship between caffeine ingestion and heart disease. However, there can be exceptions to this rule in that some may react differently to caffeine than others.

My Advice: Check with your physician if you are experiencing elevated blood pressure or arrhythmias.


Caffeine beverages can be worked into an athletes meal plan as long as you pay attention to overall daily hydration, continue to eat/drink the recommended calcium products, and follow an overall balanced meal plan that meets your sports- specific nutrient needs.

Stephanie Nunes is a Registered Dietitian and runner residing in San Luis Obispo, California. Her private practice is "Rock Solid Nutrition" and she provides individual counseling, on-line counseling, lectures or presentations for specific groups, and nutrition related articles. If you would like to contact Stephanie for any of these services, her e-mail address is