By Page Love, MS, RDN, CSSD, LD, USPTA
Juicing has been popular for decades to increase fruit and vegetable consumption and is considered a popular type of fad diet, but can it help your tennis performance? Well, depending on what your goals are, taking in fresh juices can certainly help with your fluid and antioxidant intake, but juicing as your primary meal intake of nutrition, or as the only pre-match or post-match fluid choice, can impact your tennis play negatively. Let’s look at the science.
First, juice composition is limited to just the nutrients in fruits and vegetables, mostly antioxidant vitamins and minerals, some of which are important electrolytes lost in sweat. Unfortunately, juice does not replenish what most tennis players lose in their sweat, especially in our infamous Atlanta heat. Most tennis players need to replenish lots of fluid, sodium, chloride, potassium, magnesium, and calcium. Juices provide excellent sources of fluid and potassium (and even provide additional antioxidant vitamins), but most juices do not contain adequate sodium, calcium, or magnesium — the most common electrolytes lost in sweat. Most tennis players lose much higher levels of sodium and much lower levels of potassium in sweat. When we consume higher levels of potassium, we cause a diuretic effect to occur, which means we are at risk for flushing out or losing more fluids, the exact opposite of what tennis players should aim to do.
In a recent article from the European Journal of Applied Physiology, the composition of sweat for sodium, chloride, and potassium in both low and moderate intensity exercise in the heat for 90 minutes contained the following ranges of electrolytes: sodium (659 mg to 1565 mg), chloride (931 mg to 238 mg), and potassium (102 mg to 194 mg).
An example of juice mineral composition for a typical liter of a “green juice” made from one cup of spinach, two celery stalks, one cup of kale (approximately three leaves), two cups of romaine (approximately three leaves), one cucumber, one green apple, and half a lemon or lime, contains the following electrolyte and carbohydrate: sodium (35 mg/L), potassium (357 mg/L), and carbohydrate (10 g/L).
This shows that common green juices do not contain the appropriate proportions of what tennis players lose in sweat. According to the Journal of Comprehensive Physiology, ranges of electrolytes levels present in typical sport beverages formulated to replace sweat losses, range as the following: carbohydrate (60-90 g/L), sodium (180-630 mg/L), chloride (180-216 mg/L), and potassium (54-90 mg/L).
So, what is the answer if you enjoy juicing and want to enhance your tennis performance? Dietitians encourage you to consume a variety of fruits and vegetables and yes, some of this may be obtained from juices, but juices are limited in critical nutrition for the sport nutrition needs of a tennis player. Tennis players should consume a variety of essential nutrient sources, especially complete protein sources that are critical for rebuilding muscle and bone. Juices do not replace the nutrition found in meat protein and dairy products, nor do they replace the muscle energy sources needed for long tennis matches.
To conclude, consuming a sport beverage that contains sodium in the levels mentioned above during the pre-match and on court timing intervals has been shown to appropriately hydrate and potentially enhance tennis performance. Additionally, consuming a protein beverage, such as chocolate milk containing between 15-25 grams of protein, within 15-45 minutes after play is more appropriate than just a juice alone to enhance rebuilding of lost muscle and replenish electrolyte losses more adequately.
It is important to not put all our eggs in one basket when it comes to making recommendations for one food group or one type of product for fully meeting the nutritional needs for fueling for tennis play. Sorting through the myths and understanding the physiology of the body’s needs, as well and a more complete understanding of sport nutrition, is important. Watch out for diet fads and claims; these can easily cause decreases in performance and increase risk of heat illness versus better managing it!
Page Love is an avid ALTA participant and sport dietitian/nutrition advisor for the WTA and ATP professional tours, served on the USTA sport science committee for 25 years, and has a private practice in Sandy Springs. You can reach her at nutrifitga.com. This fall, Page will be dancing for EDIN, Education and Insight in Eating Disorders, with her dance team “Love Your Body with Tennis” to raise funds for outreach community programming in local school to help in education on healthy eating and body image and improving self esteem in Atlanta’s youth. Please visit myedin.org to support our important cause!