Dietary restriction before surgery may reduce complications
BOSTON, MA - All would agree that undergoing surgery is a stressful situation and exposes one to the risk of complications, including death. Anyone facing a surgical procedure would welcome any advice that would reduce the risk of complications and improve outcome.
On January 25, researchers at the Harvard School of Public Health (Boston, MA) published the results of a study in the journal Science Translational Medicine. They reported that a period of semi-starvation before surgery may soon be a recommendation for patients scheduled for a surgical procedure.
It is well known by scientists that dietary restriction, or reduced food intake without malnutrition, increases life span, health span, and acute stress resistance in organisms from simple yeasts to nonhuman primates. It is also known that dietary restriction can be beneficial for human health. For example, studies have shown that a period of dietary restriction has many beneficial effects, including reduced cholesterol and blood pressure. Despite those facts, dietary restriction has not been widely applied to human clinical situations. Thus, the researchers exposed mice to a diet in which the amount of food ingested was not limited; however, certain essential nutrients were lacking from it. Their goal was to determine whether such a diet would increase their resistance to surgical stress. They found that a protein-restricted diet for six to 14 days of total protein deprivation protected against renal (kidney) and hepatic (liver) ischemic (decreased blood flow) injury, resulting in reduced inflammation and preserved organ function. This finding was noted both with the removal of the single essential amino acid tryptophan or the complete removal of all protein from the diet.
After a period of protein restriction, blood flow was temporarily cut off from their livers and kidneys. That insult is similar to what occurs during a heart attack or stroke and heart attack; it also can occur in organs during long and complicated surgical procedures. The researchers theorized that restricting protein, but not sugar or fat, appeared to produce an ancient evolutionary response with many consequences, one of them a reduction of inflammation. “What’s surprising is that you can do it for a really short period of time and still get a benefit,” noted lead researcher James R. Mitchell.
Currently, individuals are recommended to not consume any foods or liquids beginning at midnight of the night before surgery; however, that recommendation is designed to reduce the risk of vomiting undigested food products after the anesthetic is administered. If this occurs, some of the material might be aspirated (sucked) into the lungs. This occurrence can result in fatal complications. The findings of this study suggest that, if at all possible, preoperative preparation should begin a week or two before surgery. (Obviously, no prep time is available for an emergency surgical procedure (i.e., serious automobile accident).
The study authors caution that their study does not negate the belief that people who are well nourished are the best candidates for surgery. They explained, “Our studies were performed in young, healthy rodents; it will be necessary to determine whether this approach will work when needed most, such as in elderly or obese individuals.”
In the study, the researchers allowed eight mice to eat as much as they wanted of a protein-free chow for six days. Another group of rodents ate a normal diet. The artery and vein serving each kidney were then clamped, cutting off blood flow and oxygen for 35 minutes. Within a week, 60% of the mice on the normal diet suffered kidney failure and died. All of the protein-restricted rodents survived. The diet lacking protein appeared to protect against reperfusion injury, which is damage to cell membranes, DNA, and enzymes caused by compounds created when oxygen-rich blood returns to the blood-starved tissue. An influx of white blood cells can exacerbate the situation by triggering further inflammation.
Proteins are compounds of amino acids that are linked together in long chains. The body can make some amino acids; however, eight cannot be produced; thus, one must obtain these amino acids—known as essential amino acids—from food products. The researchers conducted a second experiment, in which the single amino acid tryptophan was removed from the mouse diet. This restriction was also found to have a protective effect. Although the evolutionary advantage of this effect is unknown, it probably involves “metabolic triage” in times of starvation. (Primitive man was frequently exposed to periods of feast and famine.) When there are not enough starting materials to make all the proteins the body requires, certain production lines may be shut down earlier than others. The inflammatory and immune response may be among the first to be sidelined.
The researchers conducted another study with the drug halofuginone, which mimics deprivation of proline, an amino acid essential during times of illness or stress. Three days of the medicine activated the “starvation response” and protected the mice.
Reference: Science Translational Medicine