When we think of malnutrition, we tend to conjure up images of starving, impoverished children with obvious height and weight defects. It’s also generally held that malnourishment is solely the result of food insecurity and that any immune problems result from that unhealthy diet. But when it comes to the relationship between the two, many experts wonder which is the chicken and which is the egg.

“If the body experiences deficiencies in energy and nutrients and excesses in pollution from cell waste and other non-nutritive substances, an imbalance is created,” Dr. T.K. Stone, author of The Fertile Ground, told Medical Daily in an email. "It is a simple supply and demand concept. The automobile cannot run without gasoline and the body struggles without an abundance of energy and nutrients, especially the brain and immune system.” And, he added, “if the system is stressed out with excess artificial pollutants, it is doubly stressed.”

Researchers from Queen Mary University in London have produced experimental evidence showing that defects in immune function in malnourished people, including a reduction of white blood cells, weak skin and gut membranes that pathogens can break through, and malfunctioning lymph nodes, are present at birth and contribute to malnutrition throughout life. Instead of focusing on providing a healthy diet in these cases, they recommend targeting immune pathways to treat the complications associated with malnutrition.

“We’ve known for decades that malnourished people tend to die of infection rather than wasting or stunting, which is a clinical feature,” Claire Bourke, a postdoctoral research assistant in the Centre for Genomics and Child Health at Queen Mary University, told Medical Daily. But, she said, “we haven’t really had the capabilities to be able to show that. Part of the reason why is because in people and in animal models of malnourishment there are so many things going on. They’re losing weight, they’re smaller, and they’re less well holistically. Since the immune system overlaps with so many systems, it’s difficult to dissect its specific role.”

Bourke said that recent advances in the study of gut microbes and epigenetics, inheritable marks that aren’t encoded in the genome but are affected by the environment, has let scientists look into previously unexplored areas. So have tests that count white blood cells, T lymphocytes, protein electrophoresis in blood and urine, immunoglobulin levels, and other substances released by the immune system. Since then, different studies have spawned a debate over the relationship between malnutrition and immune dysfunction and which comes first. People tend to develop immune dysfunction when they don’t consume enough calories or consume excess fat and sugar. This is recorded in their DNA and passed down to their children. This inherited immune system disruption can result in malnutrition among children with a healthy diet even after multiple generations.

“Research in the past five years has been able to generate this hypothesis that the immune system is part of the causality of malnutrition,” Bourke explained

Bourke and her team’s findings show that malnourished children are much more likely to die as the result of common infections than starvation. Although height and weight defects show the external impact of not getting enough nutrients, the researchers were more interested in the variety of inflammation-producing conditions caused by malnutrition, such as impaired gut function, weakened responses to new infections, and a resulting high metabolic burden.

The most common outcome of malnutrition is stunting, when children fail to meet their height potential. Around 159 million children under the age of 5, more than half of which live in Africa and Asia, experience stunting due to malnutrition. Other studies have shown that adults who survive malnutrition as children suffer from an increased risk for high blood pressure and poor heart development. However, the research team found that infection is still the biggest threat malnourished people face, and it’s not something that only developing countries have to worry about.

According to the U.S. Department of Agriculture, 17.4 million households in the U.S. suffer from food insecurity, including 3.7 million that are unable to provide an adequate amount of nutritious food for children. Evidence has shown that malnutrition contributes to the deaths of 3.1 million children around the world each year. Food insecurity is also prevalent among the elderly, people living on their own, and college students.

The current standard of care for malnourished children is a healthy diet packed with nutrient-rich and calorie-dense foods. Doctors will also prescribe antibiotics to treat systemic infections that are caused by a lack of nutrients. Bourke noted that poor nutrition can result in a host of problems with inflammation and these treatments do not directly remedy them. Her research team plans on determining whether restoring immune functions can improve the outcomes of malnutrition.

“Malnutrition, both undernutrition and overnutrition, presents a very proinflammatory environment,” Bourke added. Patients “have high levels of inflammatory markers and they’re very sick on lots of levels, but targeting inflammation per se has never been done. But, there have been small-scale pilot studies using anti-inflammatories for people with gut dysfunction and undernutrition that have shown promising results. Hopefully that’s something we can look into at a larger scale.”

Source: Berkley J, Prendergast A, Bourke C. Immune Dysfunction as a Cause and Consequence of Malnutrition. Trends in Immunology . 2016.