Juice Fasting

What is Juice Fasting?

by: Michael Sapko MD, PhD

Juice fasting, juice dieting, and juice detox are terms used to describe the consumption of juice without eating any other food. People that advocate juice fast diets suggest drinking only fruit and vegetable juices (with water) for between one to 14 days. This juice fasting paradigm has been touted as a way to detoxify or “detox” the body of unwanted chemicals and toxins.

Unfortunately there is little evidence that these juice-only diets provide any detoxification beyond what our liver and kidneys can achieve normally. One small study (five, healthy men) showed that dieters enjoyed a slight improvement in their blood cholesterol levels by juice fasting for a short period of time.¹ Most experts would agree, however, that “detox diets” like juice fasts are probably more harmful to the body than helpful,^2,3yet it is difficult to find clinical trials showing the efficacy, safety, or even the danger of such dietary practices.

Is Juice Fasting Safe?

One of the miracles of the human body is that it can tolerate many of the things that we do to it. If you are a young adult and healthy, there is little damage that a juice fast can do to your body over one to three days. As long as you continue to consume enough water (both in the juice and by itself) your body will make it through the fast without any permanent problems. Of course, this is the same reasoning that would apply if you were to simply stop eating for a few days, too. Your body would react in much the same way: it would digest the muscle and fat that you already have in your body to supply the cells with the food they need to survive.

The problem arises when people that are not young or healthy decide to juice detox. People that have certain diseases should not juice fast at all, for example, individuals with diabetes. In other groups, the risks of juice fasting are higher than they are in the general population. On the other hand, perhaps we think we are healthy, but when we start a rather restrictive diet such as juice fasting, we might find out that we were not quite as healthy as we thought we were.

Who is Healthy Enough for a Juice Fast?

Most young and generally healthy people will survive a juice fast unscathed. However, realize that you should have enough muscle mass and fat on your body to supply yourself with the energy you will not otherwise be getting during the fast. Juices have very little protein,⁴ so your body will take protein from your muscles to meet its needs.⁵ You will also need a small amount of fat. Your body will liberate this from fatty stores, but keep in mind that during near-starvation, you will lose muscle mass before you lose fat. Therefore if you are underweight, malnourished, or have an eating disorder or nutrient deficiency, you are not healthy enough for a juice diet.

Also keep in mind that in certain circumstances, the body needs more nutrients than usual. If you have cancer, an acute or chronic infection, any autoimmune disease, or other chronic illness, your body is using more energy than you might imagine.^6,7 To deprive the body of a balanced diet at these times can be unhealthy. Growing children and pregnant or nursing women should not juice fast since these are states of increased metabolism and body growth. If any of these apply, you are not healthy enough to juice fast.

If you are taking any over the counter or prescription medication, or any herbal or natural remedy, you should seriously consider whether it is a good idea to perform a juice fast. Certain medications, such as warfarin (Coumadin), are extremely sensitive to changes in diet.⁸ It is never a good idea to stop a prescribed medication without consulting your doctor first.

Juice Fasting and Diabetes

Diabetes mellitus is a disease in which the body does not make insulin (Type 1) or the cells of the body are insensitive to insulin (Type 2). Insulin in necessary for sugar to cross from the bloodstream into the cells where it can be converted to energy. In both Type 1 and Type 2 diabetes, sugar tends to accumulate in the bloodstream, which leads to poor wound healing, vision disturbances, heart disease and over time causes eye, kidney, and nerve,problems. Patients with diabetes are encouraged to eat complex carbohydrates when possible and only consume simple sugars under certain circumstances.⁹

Unfortunately, fruit juice is almost entirely made up of simple sugars.⁴ Vegetable juices are much the same way. When one consumes a large quantity of simple sugars, they are rapidly absorbed into the bloodstream, making blood sugar (glucose) rise rapidly. This is potentially dangerous for diabetics and may increase the risk of diabetes in some people.¹⁰Moreover, fruit and vegetable juices are largely without dietary fiber (since most of that content stays in the juicer on with the rind). Dietary fiber is an excellent food to improve insulin susceptibility and prevent diabetes.^11,12

If You Want to Juice Fast, Be Safe

1. If you are going to engage in juice fasting, a rather extreme detoxification diet, consult your doctor in advance to make sure you are healthy enough to juice diet. If she warns you against the juice fast, listen to her.
2. When planning your juice fast, make sure you consume a wide variety of fruits and vegetable juices so that you get all of the necessary vitamins and minerals. Remember that you will not be getting the protein and fat that your body needs during the fast. This means that you will lose lean muscle mass and fat.
3. Since you will be depriving your body of fiber during the fast, it makes good sense to consume psyllium husk or some other source of quality dietary fiber. In fact, dietary fiber will likely do more to cleanse your system than a juice fast.
4. Of course juices have water in them, but not enough to get you through the fast. Make sure you drink plenty of water.
5. Do not juice fast for more than three days, especially if it is your first time. After that, the risk of health issues—even in healthy people—increases.
6. Watch carefully for signs of dangerous side effects and stop juice fasting immediately should they occur. Lightheadedness, dizziness, and feeling faint may mean you are hypoglycemic or even hyperglycemic. When severe, these two situations can kill (however not likely in a non-diabetic). These symptoms could mean you are dehydrated, as well. Remember that diarrhea is a common occurrence with juice fasting. When diarrhea occurs, know that you are losing fluid and nutrients.Hunger sensations are to be expected, but other abnormal sensations during a juice fast should be taken seriously.

References

1. Huber R, Nauck M, Ludtke R, Scharnagl H. Effects of one week juice fasting on lipid metabolism: a cohort study in healthy subjects. Forschende Komplementarmedizin und klassische Naturheilkunde = Research in complementary and natural classical medicine. Feb 2003;10(1):7-10.

2. Association AD. Consumer Diet and Lifestyle Book Reviews.  http://www.eatright.org/dietreviews/.

3. Griffin J. Health and fitness series–3. Popular dietary fads: how should health professionals respond? The journal of family health care. 2003;13(3):65-68.

4. USDA Nutrient Database. http://www.nal.usda.gov/fnic/foodcomp/search/.

5. Ding X, Price SR, Bailey JL, Mitch WE. Cellular mechanisms controlling protein degradation in catabolic states. Mineral and electrolyte metabolism. 1997;23(3-6):194-197.

6. Long CL, Schaffel N, Geiger JW, Schiller WR, Blakemore WS. Metabolic response to injury and illness: estimation of energy and protein needs from indirect calorimetry and nitrogen balance. JPEN. Journal of parenteral and enteral nutrition. Nov-Dec 1979;3(6):452-456.

7. McMahon MM, Bistrian BR. The physiology of nutritional assessment and therapy in protein-calorie malnutrition. Disease-a-month : DM. Jul 1990;36(7):373-417.

8. Pedersen FM, Hamberg O, Hess K, Ovesen L. The effect of dietary vitamin K on warfarin-induced anticoagulation. Journal of internal medicine. Jun 1991;229(6):517-520.

9. Crapo PA. Simple versus complex carbohydrate use in the diabetic diet. Annual review of nutrition. 1985;5:95-114.

10. Bazzano LA, Li TY, Joshipura KJ, Hu FB. Intake of fruit, vegetables, and fruit juices and risk of diabetes in women. Diabetes care. Jul 2008;31(7):1311-1317.

11. McKeown NM. Whole grain intake and insulin sensitivity: evidence from observational studies. Nutrition reviews. Jul 2004;62(7 Pt 1):286-291.

12. McKeown NM, Meigs JB, Liu S, Saltzman E, Wilson PW, Jacques PF. Carbohydrate nutrition, insulin resistance, and the prevalence of the metabolic syndrome in the Framingham Offspring Cohort. Diabetes care. Feb 2004;27(2):538-546.

About the Author

Michael T. Sapko received his MD and PhD degrees from the University of Maryland. He practiced internal medicine at Mercy Medical Center in Baltimore. In 2006, Dr. Sapko established and currently operates a medical and science consulting firm that provides literature reviews, scientific and clinical study design planning, and peer-reviewed journal article writing. Dr. Sapko was commissioned to provide an unbiased, objective review of the subject.

The information in this report is for informational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. You should speak with a licensed physician before engaging in a new dietary regimen, especially if you have existing health problems. Dr. Sapko does not endorse the use of juice fasting.