Animal studies have revealed that being separated from the mother as a child or experiencing other traumatic incidents during childhood can change behavior and induce stress-related behavioral changes. It has also been seen that when offered tasty and palatable food, this stress is lessened to some extent. This study attempted to explore this fact by subjecting rats to separation from their mothers at birth, to induce stress, and then offering them a high-fat diet on weaning. The results showed that when given high-fat diets, the experimental animals had significant reduction of stress.
In humans as well as animals, stress and traumatic incidents during childhood are often associated with stunted neural development and psychological issues like stress and behavioral abnormalities in adulthood. The traumatic events may range from neglect to abuse. In animals, it is noted that a similar trauma can be induced if a newly born rat pup is separated from its mother for a period. This stress is detected by the rise of the hormone corticosterone in the blood. This behavior has been studied in detail, in multiple studies. However, no studies conducted have explored the fact that the stress may be reduced if the rat pup is offered tasty food when it is separated from its mother.
- For this study, mother mice with newly born litters were included.
- The pups were divided into groups – non-handled by humans; those that were separated from their mothers for a short period of 15 minutes; and those that were separated for 180 minutes. These pups were all between 2 and 14 days of age.
- At the age of more than 20 days, these pups were further divided into two groups. One group received standard laboratory food and the other group received a high-fat tasty diet (biscuits, cakes, meat pies or dim sum).
- The levels of stress were analyzed among the pups using the sucrose preference test and elevated plus maze test.
- The results showed that non-handled baby rats consumed less food compared to those that underwent short or long separations. The tests also detected that male rats who were non-handled as well as those who were long separated, showed more anxiety when fed with a standard diet. On the other hand, male rats that were fed a high-fat diet showed less anxiety.
- Female rats that were long separated also showed more anxiety. But food had no effect on anxiety levels of female rats.
- Lack of interest is a common sign of depression. It was seen that male rats that were long separated and ate standard food, developed this condition, but female rats did not.
- When blood levels of corticosterone as a marker for stress were measured, it was seen that the levels were lower in the short separation group compared to those who were non-handled or were in the long separation group. Diet did not affect the levels of corticosterone.
The authors have discovered some unclear relations between food-related behavior linked to stress and some hormones and enzymes. One of these is the hormone NPY that is present in a small gland in the brain called the hypothalamus. The role of NPY in eating regulations and behavioral responses in rats subjected to maternal separation needs further research work. In addition, further investigation is also required to understand the differential effects of separation and non-handling on hypothalamic NPY mRNA across genders.
The authors conclude that, “the extent of environmental deficit and the quality of maternal care determines the risk of developing depression and anxiety later in life.” The results showed that male rats – either non-handled or separated for a long time – developed anxiety; but non-handled female rats showed no such trend, while those separated for a long period did develop anxiety. The results also showed that lack of interest is something that was found in long-separated male rats, but not in female rats. The female rats also did not show any reduction of stress after taking palatable foods. The authors suggest further studies to explore the deeper physiology that is linked to stress and the concept of comfort food.
For More Information:
Palatable Cafeteria Diet Ameliorates Anxiety and Depression-like Symptoms Following an Adverse Early Environment
Publication Journal: Psychoneuroendocrinology, 2010
By Jayanthi Maniam; Margaret Morris
From the University of New South Wales, NSW, Australia
*FYI Living Lab Reports Are Summaries of the Original Research.