Does diet alter damage from environmental exposures?
By Angela Spivey
Can something as simple as what people eat determine whether powerful chemicals, such as polychlorinated biphenyls (PCBs), damage their bodies? Possibly so, according to a new NIEHS-funded study by Bernhard Hennig, Ph.D. professor of nutrition and toxicology and director of the Superfund Research Program (SRP) at the University of Kentucky (UK), and other researchers.
“The evidence is very strong from animal studies and correlation studies that those who are more nutritionally sound are more resistant to chemical insults,” Hennig said. Specific elements in the diet can either stop or promote some of the damaging processes, such as oxidative stress and inflammation, which follow exposure to many environmental chemicals.
Prevention through nutrition
Animal studies have shown that PCB exposure can induce atherosclerosis, for example. But when Hennig fed mice an olive oil-enriched diet and then exposed them to PCBs, the chemical had little effect on their fatty acid profiles. Mice that ate a corn oil-enriched diet showed significant changes in serum fatty acids after PCB exposure. So the type of fat in the diet, not just the amount of fat, may make a difference in the cell damage that is triggered by environmental chemicals. In addition, Hennig and other researchers have found that antioxidants, such as vitamin E and flavonoids, as well as a high ratio of omega-3 to omega-6 fatty acids, can reduce cell damage caused by PCBs and other pollutants.
This and other evidence leads some researchers to recommend that future environmental health research and pollutant risk assessment approaches incorporate nutrition and dietary practices. “In the past, risk assessment was based on one chemical, but we now know that it’s much more complicated than that — we are exposed to mixtures of chemicals,” Hennig said. Incorporating nutrition into risk assessment of environmental chemicals extends that idea. “Other factors, such as nutrition, may either increase the response to chemicals or reduce it,” Hennig said.
The idea that diet contributes to health is ancient, but efforts to understand how specific nutrients influence disease risk from environmental pollutants is novel, stated William Suk, Ph.D., director of the NIEHS Superfund Research Program. “If we are going to assess the risk of an individual, we have to be able to consider a variety of factors and cofactors, and one of the big things is what we eat and drink,” Suk said. “Understanding nutrition, and how it modulates risk and potentially prevents disease, is part of the new NIEHS strategic plan currently under review.”
Expanding research with human subjects
Much of the evidence for the nutrient-pollutant connection comes from animal studies. But well-defined, prospective epidemiological studies with repeated measures of exposures to both environmental chemicals and nutrients are needed, according to Somdat Mahabir, Ph.D., program director with the Epidemiology and Genetics Research Program of the National Cancer Institute. Mahabir is interested in epidemiological research aimed at understanding whether dietary patterns and specific nutritional factors are useful in offsetting a portion of the disease risk attributable to environmental pollutants.
“The idea that nutritional factors can modulate the toxicity of environmental pollutants and, thus, have consequence for human disease risk is an interesting concept with potentially important public health significance. However, well-defined epidemiological studies to test this hypothesis have not been done, due to methodological challenges,” Mahabir said (see text box). Data from human prospective studies could be used to model, for example, whether people exposed to high levels of pollutants and high levels of dietary fat are at higher risk for diseases, such as cancer, than individuals exposed to high levels of pollutants and low levels of fat.
Even with the best remediation efforts, it’s nearly impossible to remove all the chemicals at a given site, according to Hennig. Nutrition may become the simplest form of risk reduction. The UK SRP uses nutrition education as part of its community engagement efforts. “Nutrition may be a very meaningful way to make people and animals less vulnerable to chemical stressors,” Hennig said.
Hennig B, Ormsbee L, McClain CJ, Watkins BA, Blumberg B, Bachas LG, Sanderson W, Thompson C, Suk WA. (http://ehp03.niehs.nih.gov/article/info:doi/10.1289/ehp.1104712) 2012. Nutrition can modulate the toxicity of environmental pollutants: implications in risk assessment and human health. Environ Health Perspect; doi: 10.1289/ehp.1104712 [Online 22 February 2012].
Hennig B, Reiterer G, Majkova Z, Oesterling E, Meerarani P, Toborek M. 2005. Modification of environmental toxicity by nutrients: implications in atherosclerosis. Cardiovasc Toxicol 5(2):153-160.
(Angela Spivey is a contract science writer for the NIEHS Superfund Research Program.)
Teasing out the role of nutrition in risk assessment
There are many other challenges involved in incorporating nutrition into risk assessment. In cross-sectional human studies that have been conducted, the effects of nutritional interventions, such as antioxidants, have been less robust than in animal studies, and more research is needed to understand this variability in humans. This variability is likely influenced by many factors, including genetic polymorphisms and epigenetic effects of nutrition and pollutants, Hennig and colleagues noted, adding that risk assessment and nutritional intervention should consider the implications of research in nutrigenetics and nutrigenomics. Also of concern is the long-term effect of supplementing nutrients that can be used as therapeutics, such as antioxidants and fatty acid supplements. In addition, there is a need to learn more about the bioactive targets that various nutrients act upon.