DEAR DR. BLONZ: Something that is hyped with intermittent fasting and ketogenic diets is that they promote autophagy, which is described as cleaning out, detoxifying and renewing the body. I remain curious whether and to what degree this might be true, and how it works. -- F.S., Tulsa, Oklahoma
DEAR F.S.: The adult human body is remade regularly by way of cell replacement; directions for this are in our genes. But, to work as programmed, there must be access to raw materials, nutrients, and available energy when and where needed (especially vital during pregnancy and growth spurts).
In adults, turning over the fastest are the red blood cells and the cells lining the mouth and gastrointestinal tract; this helps explain why nutrient deficiencies or other medical or medication issues tend to be felt in these areas first. Regarding other parts of the body, the cells of the liver turn over faster than muscle cells, which turn over faster than bone cells.
The point to remember is that while autophagy renews, it does not make us "new and improved" -- our bodies remain governed by our genes, the foods we eat and the lifestyle we lead -- check out b.link/x555gk.
The materials for the rebuilding come from essential nutrients in the foods we eat, along with those provided by the body's recycling system. Autophagy (aw-TAHF-uh-gee), which translates literally as "digesting oneself," is the process of cell breakdown that facilitates the disposal of unwanted cellular debris while holding on to substances suitable for reuse. Sounds great -- so who wouldn't want eating plans that promote cell renewal?
Autophagy's expression is not fixed -- it gets prioritized according to the needs of the moment, as efficiently as possible. For example, suppose the body hasn't been getting enough of a particular essential mineral. The body's response is to be more conservative with what it has, and the kidneys become stingy in allowing that mineral into the urine. Autophagy aligns with such priorities to facilitate the availability and reuse of any materials in short supply.
Nutrient intake stops during a fast, and with a ketogenic diet you may not get the full complement of the body's nutritional needs. One thing both diets cut is carbohydrate intake.
Digestible carbohydrates get converted to glucose, which is the only fuel that can be burned by our red blood cells and is the brain's preferred fuel (the brain uses about 70% of the glucose in the blood for its energy). The body has a minimum blood glucose level; if sufficient amounts are not in the foods we eat, the body breaks down resources to support the minimum level. This is potentially lifesaving as, unlike fat, glucose is the only substance that can release its energy without oxygen. It explains how we can walk up a hill or stairs without first taking deep breaths to increase the oxygen level in the blood. After several steps, the body has you breathing deeper as it shifts to burning fat for energy.
The bottom line is that autophagy is a complex process that should not be spun as an eating plan to promote cell renewal. Keeping your body supplied with its essential nutrients through a plant-based, whole food, healthful diet will keep this process functioning properly to help achieve normal cell turnover, in which the body recycles the good stuff and takes out the trash as needed.
Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.