Juice fasting is a short-term detoxification strategy that involves consuming only fresh fruit and/or vegetable juices. Solid foods, especially those derived from animals and grains, are avoided while juice fasting. The advantages of juice fasting are not well established by scientific research, although many anecdotal reports claim a wide variety of health benefits. In order to minimize loss of muscle mass while juice fasting, you should include fruits and vegetables rich in amino acids or consider adding protein powders. Exercising your muscles while fasting is also a good idea. Consult with your doctor before embarking on any type of radical dietary change.
Juice fasting is considered a relatively safe and natural way to detoxify your body, boost immunity and lose weight, according to the "Textbook of Nutritional Medicine. Most juice fasts last for about three days, although it is not uncommon for them to last up to a week. Consuming between eight and 10 medium-sized glasses of juice each day is typical of most juice fasts. The basic premise is that fruits and vegetables are excellent low-calorie sources of many vitamins, minerals and various phytonutrients that exhibit antioxidant and antimicrobial properties, but they don't contain any saturated fats, preservatives, artificial sweeteners and many other additives that are sometimes perceived as harmful. However, most fruits and vegetables are poor sources of protein, so extended periods of juice fasting may initiate muscle wasting, which is the atrophy of muscle fibers.
Muscles and Protein
Muscle tissue is made from protein, which in turn is made from long chains of amino acids. In order to build, maintain or repair muscle tissue, dietary amino acids are required. Meat, fish, dairy products and legumes are excellent sources of amino acids, but most fruits and vegetables are lacking in the essential amino acids, which your body cannot synthesize, according to "Nutritional Sciences for Human Health." Muscles weaken and shrink from lack of use, but they can start to waste away if there is a severe lack of dietary amino acids or not enough calories, which forces the body to metabolize, or break down, amino acids into glucose for energy.
Fruits and vegetables commonly used for juice fasting include carrots, beets, celery, parsley, watermelon, apples, grapes and lemon, which are all highly nutritious, but only carrots are a significant source of amino acids, according to "Superfoods: The Healthiest Foods on the Planet." Other fruits and vegetables higher in amino acids include papaya, coconut, kiwi fruit, peaches, tomato, spinach, asparagus, broccoli, alfalfa and wheatgrass juice. If the taste of these fruits or vegetables does not appeal to you, consider adding specific amino acids important for muscle building, such as glutamine and carnitine, or protein supplements, such as whey, soy or hemp powders. And don't forget to do some resistance exercises while you're juice fasting, such as light weightlifting or swimming, which should at least maintain your muscle mass.
Too much juice can cause severe gastrointestinal symptoms, such as abdominal bloating, flatulence and diarrhea, so consider drinking more water during the day instead. Further, your body needs some fat, cholesterol and vitamins that are not found in fruit and vegetable juices, so consult with your doctor if you plan on fasting for more than a week.