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Fasting can slow tissue repair


Dear Dr. Blonz, I would like to know your thoughts about fasting to maximize energy, cellular renewal and repair, and bodily cleansing. Thanks. -SK, Boston, MA.

DEAR SK, The idea of fasting has been around for a long time and is an integral part of many religions. The origins are intertwined with ancient beliefs that fasting leads to a purification of the soul or spirit. From a health perspective, there can be benefits to fasting, but they may not be what you would expect.

There is more on the plate than can be covered in one column, so I am going to break it down into two servings: This week I will focus on the idea of fasting for energy, cellular renewal and bodily repair, and the next installment will cover the concept of fasting for body cleansing. For dessert, I will tackle situations in which fasting may represent a risk to health.

To start, we need to understand that glucose (blood sugar) is the preferred fuel for the brain and nervous system. It is the only fuel that the red blood cells use, and it is the body's primary source for instant energy. I say "instant" because it is the body's anaerobic fuel, one that does not require oxygen to release energy. Glucose is what allows you to move from a resting position to walking up a flight of stairs without first taking deep breaths to increase the level of oxygen in the blood stream. There are small stores of a form of glucose in liver and muscle, but these don't last very long. When they're used up, the body becomes desperate for glucose to the point that it begins to break down protein tissues (muscles and organs) to get at amino acids, which can be turned into glucose.

It is not advisable to use protein this way, as it is needed to make muscles, organs, blood cells, nerves, bone and brain tissue, enzymes, hormones, antibodies, chemical messengers, the DNA and RNA used to form the genetic code of life and our hair and nails. The daily requirement for protein provides amino acids to replace worn out cells, but during a fast, the body is forced to continually recycle its own amino acids. It comes up short because some are always being recruited to form glucose. During the first days of a fast, approximately 75 grams per day of the body's own protein gets used to satisfy our need for glucose. This means that tissue growth and repair slows down. Normally, about 10 percent of our daily calories are expended to run the digestive system.

One of the claimed benefits from fasting comes from the idea that not eating allows the digestive system to rest, and this frees up this energy for the body to use to improve health. This is illogical. It's like quitting your job to save the money spent on commuting. Then there is the fact that the digestive system is designed for multiple daily workouts. As with most muscles, when exercise stops, the muscles begin to atrophy over time.

Bottom line: When you stop eating, your body's supply of energy and raw materials decrease. Everything slows down in the interest of conservation, but this will also include the rate of tissue repair.


Dr Blonz Do you have a question that involves nutrition, health and wellness? Dr. Ed Blonz holds an M.S. and Ph.D. in nutrition, and has more than 30 years of experience in the fields of nutrition, foods and health. He is the author of eight books and writes the nationally syndicated column, "On Nutrition," available through Universal Press Syndicate.

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Copyright Ed Blonz, Ph.D.