What we eat is considered an environmental factor that influences health, in positive and negative ways. Healthy diets with an optimal balance of nutrients help people accomplish daily physical activities and mental processes. Within your diet, a deficiency or excess of certain nutrients can affect health.
The term diet refers to foods and beverages consumed over time in all settings, such as worksites, schools, restaurants, and the home. Diet also often means a specific nutritional plan or eating pattern.
Nutrition is the process of consuming, absorbing, and using nutrients from food that are necessary for growth, development, and maintenance of life.
What Are Nutrients?
Nutrients give your body energy and enable bodily functions. They are usually classified in two major groups:
- Macronutrients, in the form of protein, carbohydrate, or fat, primarily to provide energy to your body. The different macronutrients serve different energy pathways and functions in the body. Energy from macronutrients in food is measured in units called calories.
- Micronutrients, known as vitamins and minerals, are required by the body in minute amounts. They protect and promote various bodily functions, including processing energy from macronutrients. Although critical to health, micronutrients do not supply energy.
What Should People Eat?
As reflected in the federal Dietary Guidelines for Americans, scientific evidence shows that healthful eating patterns can help people achieve and maintain well-being and reduce their chance of chronic disease. The guidelines also say that people can enjoy foods that meet their personal needs and cultural preferences while eating healthfully.
By translating science into succinct, food-based guidance, the guidelines are intended to help the U.S. population at large choose a better diet. Specific nutritional recommendations for individuals suffering from diet-related conditions are not provided.
The Dietary Guidelines for Americans are jointly developed and issued by the U.S. Department of Agriculture and the U.S. Department of Health and Human Services. Updated every five years, they are the cornerstone for many federal nutrition programs and policies.
Why Study Nutrition and Health?
More than half of U.S. adults – 129 million people – have one or more preventable chronic diseases, such as cardiovascular disease, high blood pressure, type 2 diabetes, and some cancers, which are often related to diet and physical inactivity.
Beyond health effects, nutrition-related diseases create strains on productivity, health care spending, health disparities, and military readiness. Addressing such issues requires understanding interrelated biological and social environmental determinants, and corresponding solutions.
As a scientific field, nutrition is integral to health promotion and disease prevention. Information from many disciplines, including anthropology, biology, biochemistry, economics, epidemiology, food science and technology, genetics, physiology, psychology, and sociology, are applied in nutritional studies. Scientists consider what people eat and drink, and take as dietary supplements, during different life stages and over time. They focus on interconnections to build evidence for public policy, health system, and environmental improvement strategies.
Nutrition Research at the National Institutes of Health
The Precision Medicine Initiative is a long-term research project at NIH. This initiative aims to understand how a person’s genetics, environment, and lifestyle can determine the best approaches to prevent or treat disease.
As part of the Precision Medicine Initiative, NIH has a plan to accelerate nutrition research. While dietary guidelines and related public health approaches can help improve nutritional status across a population, researchers have growing appreciation for how different factors may affect people differently.
NIH nutrition research will help answer: what should I eat to stay healthy?
The 2020 – 2030 Strategic Plan for NIH Nutrition Research focuses on how nutrition and dietary patterns affect all health conditions and emphasizes the importance of understanding variation among people. NIEHS assists with the coordination and implementation of this nutrition research plan.
This plan is organized by four strategic goals and questions:
- Spur discovery and innovation through foundational research: What do we eat and how does it affect us?
- Investigate the role of dietary patterns and behaviors in optimal health: What and when should we eat?
- Define the role of nutrition across the lifespan: How does what we eat promote health across the lifespan?
- Reduce the burden of disease in clinical settings: How can we improve the use of food as medicine?
And the plan considers these factors:
- Dietary practices
- Environmental exposures
- Food environment
- Genetic background
- Health status
- Physical activity
- Psychosocial characteristics
What Is NIEHS Doing?
With funding and support from NIEHS, scientists are looking at whether certain nutritional components may protect people’s health when they are exposed to harmful chemicals and other environmental hazards. Scientists are also studying whether environmental factors can worsen health conditions related to nutrition or dietary patterns.
Nutrition May Reduce Harmful Health Effects From Environmental Factors
The concept of reducing risk from harmful exposures tends to mean removing or decreasing exposure to environmental contaminants. But that form of prevention can be difficult to achieve. An alternative concept is to focus on nutrients with potential to be protective or reduce the risk of harmful health effects from environmental factors.
Researchers at the NIEHS-funded University of Kentucky Superfund Research Center have an innovative, long-running program that studies if and how nutrition can reduce the risk of harmful health effects from environmental pollutants. Their research is based on the premise that nutrition should be considered a necessary variable in the study of human diseases associated with exposure to environmental contaminants.
Based on years of study, there is evidence that certain aspects of nutrition are protective and should be integral in efforts to intervene or prevent toxic health effects of some environmental factors.
For example, the researchers uncovered how a person’s diet can protect against the harmful health effects of exposure to polychlorinated biphenyls (PCBs). Now banned from production, PCBs were once commonly used in making products such as heat transfer fluids and coolant in electric transformers. They discovered that certain nutrients, vitamin E and omega 3-fatty acids, can reduce cell damage from PCB exposure and that a type of fiber found in vegetables can potentially protect against cardiovascular problems related to PCB exposure. Conversely, they also found that dietary fat that is high in linoleic acid can worsen the cardiovascular effects of PCBs.
Other Findings From NIEHS-supported Research Include the Following:
ADHD – Researchers demonstrated that low vitamin D during pregnancy was related to an increased risk of attention deficit hyperactivity disorder (ADHD), a finding that could lead to new prevention measures.
Asthma – Much of the research on nutrition and autism concerns periods before and during conception.
Asthma is a common childhood disease that disproportionately affects urban minority populations, such as Black children. Researchers discovered that vitamin D has a protective effect among children with asthma who live in urban environments with poor indoor air quality. In other words, obese children with blood levels low in vitamin D had worse asthma than children with higher vitamin D levels.
A diet deficient in antioxidants–micronutrients that help defend cells in the body–has been suggested as one reason for the asthma epidemic. The traditional Mediterranean diet typically includes foods rich in antioxidants such as vegetables, fruits, nuts, fish, and olive oil, with a low intake of meat. This diet pattern has been shown to be protective of asthma and allergic disease in multiple studies. A study funded by NIEHS found that following this type of diet reduced the chance of asthma development among children in Lima, Peru.
Autism Spectrum Disorder – Autism spectrum disorder (ASD) is a broad range of conditions that affect communication and behavior. Environmental factors and genetics are thought to contribute to ASD, which affects 1 in 44 children in the U.S.
While more research is needed on the potential role nutrition may play in the development of ASD, studies reveal promising findings.
- Taking a prenatal vitamin during early pregnancy was associated with a lower rate of ASD in a 2021 study. This finding indicates that prenatal vitamins or supplemental folic acid could be preventative for ASD.
- The younger siblings of children with ASD have a greater chance of developing the disorder due to shared genetics and similar environment. A NIEHS-funded researcher reported, in 2019, that when mothers of these children took prenatal vitamins with folic acid in the first month of pregnancy, the recurrence of autism was reduced by about half. Folic acid is the synthetic form of folate, also known as vitamin B-9, which is found in many foods, such as dark-green leafy vegetables, beans, peas, broccoli, and oranges.
Autoimmune Diseases – Lupus, an autoimmune disease, occurs when your body’s immune system attacks your own tissues and organs, affecting many different body systems. Lupus can flare up when genetically predisposed people encounter certain environmental agents, such as air pollutants, pesticides, or other chemicals. A study funded by NIEHS found that dietary micronutrients could either improve or worsen lupus symptoms. Study results suggest that dietary modification, such as more vitamin B-12, zinc, and folic acid, might be a therapeutic approach warranting further investigation in lupus patients.
Other NIEHS-funded research indicates that adequate vitamin D levels may be important for preventing immune dysfunction in older people.
Brain Health – Consuming omega-3 fatty acids, found in fish and flaxseed oil, may protect against brain shrinkage in older women who live in areas with high levels of air pollution called fine particulate matter (PM2.5).
Women living in locations with higher PM2.5 had significantly less white matter in their brains. But in those locations, women with high blood levels of omega-3 fatty acids had white matter that appeared healthier.
Cancer – More than 20 years ago, NIEHS researchers demonstrated a gene-diet interaction in a study that found isothiocyanates, a compound in cruciferous vegetables (e.g., broccoli, cauliflower, and cabbage), was protective against lung cancer.
In-house researchers at NIEHS found that vitamin D supplementation may be useful in breast cancer prevention. The study looked a group of women with a higher risk of developing breast cancer. The women who had high blood levels of vitamin D and regularly took vitamin D supplements had lower rates of postmenopausal breast cancer over a 5-year follow-up period.
Inflammation – Many epidemiological studies provide evidence that cardiovascular diseases are linked to environmental pollution. NIEHS-funded researchers found that a mix of B vitamins (folic acid, B-6, and B-12) may protect DNA in immune cells from harmful effects of PM2.5 air pollution. They found that this pollution caused changes in DNA related to inflammation and metabolism, which may be tied to cardiovascular or respiratory conditions. According to the researchers, dietary supplementation with B vitamins almost completely prevented the changes to DNA that may lead to adverse health effects.
Obesity – High lead levels during pregnancy are linked to child obesity in a large 2019 study, partially funded by NIEHS. Children born to women who have high blood lead levels are more likely be overweight or obese, compared to children whose mothers have low levels of lead in their blood. But women who take folic acid supplements during pregnancy may reduce the chance that their children are obese.
Reproductive Health – There is growing acceptance that nutrition may be related to fertility, and specifically the success of infertility treatment in women. NIEHS-funded research found that women consuming a “pro-fertility” diet that included supplemental folic acid, vitamin B12, vitamin D, low-pesticide fruits and vegetables, whole grains, seafood, dairy, and soy foods have a greater chance of live birth following assisted reproductive technologies.
The same researcher found folic acid could counter the adverse effects of air pollution on reproductive success in women using assisted reproductive technology. Air pollution can harm reproduction through a variety of biological mechanisms, including oxidative stress, endocrine disruption, DNA methylation, an altered immune response, and inflammation. Given exposure to traffic-related air pollution, pregnant women who took folic acid had a greater chance of their pregnancy resulting in a live birth.
Environmental Factors Affect Nutrition
Food Environments – A systematic review published in 2020, partially funded by NIEHS, suggests that the health of some children may be affected by food environments near schools. Researchers examined the presence of fast-food outlets, convenience stores, supermarkets, and grocery stores near schools along with measures of overweight/obesity by race/ethnicity, gender, grade, and income level.
This review found that when fast food outlets were located near schools, obesity rates were generally higher among children in all grade levels. Additional research is needed to better understand this finding, especially for children at higher risk of obesity, such as those from socio‐economically disadvantaged populations.
Food Packaging – PFAS are a group of more than 9,000 perfluoroalkyl and polyfluoroalkyl substances, a class of chemicals associated with harmful health effects, including liver damage, cancer, and impaired immunity. Due to wide-spread usage, PFAS are in the blood of nearly every American, according to the Centers for Disease Control and Prevention.
- Some PFAS have grease-repellent properties, which is why they are added to food packaging. A study found PFAS coatings on 46% of food-wrap papers and 20% of paperboard containers collected from fast-food restaurants across the U.S. This demonstrated prevalence of PFAS in fast-food packaging shows how people can be exposed to PFAS through foods they may consume.
- In a subsequent, related study, consumption of meals from fast food, and pizza and other restaurants, was generally associated with higher serum PFAS concentrations in people. In the same study, consumption of microwave popcorn was associated with significantly higher serum levels of certain PFAS chemicals.
Food Safety – Food safety studies funded by NIEHS include contaminants in common foods. In particular, arsenic, a metal-like element that can harm many human organs, presents a global food contamination problem.
Researchers measured arsenic concentrations in several rice-based products. They found high levels of arsenic in brown rice syrup, a substitute for corn syrup in many foods including toddler formula. This discovery informed the Food and Drug Administration’s Inorganic Arsenic in Rice Cereals for Infants: Action Level Draft Guidance for Industry and other federal actions and reports.
The problem of contaminants in food led researchers funded by the Superfund Research Program to develop approaches for addressing soils used to grow crops. Some are working on phytoremediation approaches that are cost-effective and ecologically friendly. Phytoremediation is a process that uses fast-growing plants in engineered systems to degrade, extract, contain, or immobilize contaminants from soil or groundwater.
One team is testing a species of a non-food crop plant called oilseed to absorb and concentrate arsenic in its stems and leaves. Once harvested, these plants could be safely destroyed through incineration. Then, the plan is for farmers to plant food crops in the soil remediated from arsenic. This project is ongoing through 2025.
Eating Fish – Eating fish can provide many health benefits, but consumers should be cautious. Some types of fish caught in certain areas are lower in mercury, PFAS, and other contaminants than other fish. Fish consumption advisories help people understand what fish are safe to eat, for whom, and in what quantities.
Researchers supported by NIEHS, for example, developed the Eat Fish, Choose Wisely guide for North Carolina residents, which includes a color-coded map for people to identify areas where they can catch fish that are safer to eat.
Food Gardening – The need for affordable, healthy foods has increased public interest in home, school, and community gardens. While urban gardens provide numerous benefits, soil contamination may be an issue. Some NIEHS-funded researchers have taken on safe urban gardening in their community engagement projects. Examples include:
Food Security – Diet is widely recognized as a key contributor to human gut microbiome composition and function. A healthy gut microbiome can help the immune system develop, protect against pathogens, and enable proper food digestion. Researchers found the gut microbiome of adults with food insecurity, a lack of access to healthy food, differed from those who were food secure. This study is significant because it focused on a social factor rather than dietary components.
The following large projects, conducted in-house at NIEHS, have research components that concern dietary patterns or nutrition.
Agricultural Heath Study – More than 89,000 farmers and their spouses in Iowa and North Carolina have been involved in this study since 1993. The collaborative research effort involves investigators from NIEHS, National Cancer Institute, Environmental Protection Agency, and National Institute for Occupational Safety and Health. This research project includes a dietary survey. A list of published papers is organized by year.
The Sister Study – From 2003 to 2009, more than 50,000 women across the U.S. and Puerto Rico, who were 35-74 years old and whose sister had breast cancer, joined this landmark research effort to find causes of breast cancer. Because of their shared environment, genes, and experiences, studying sisters provides a way to identify risk factors for breast cancer, which may lead to prevention. Participants complete health updates each year, which include dietary surveys. A list of published papers is organized by year.
Infant Feeding & Early Development Puberty Study (IFED-2) – This research study is looking at what babies eat and how they grow, including hormonal changes, into adolescence. It will improve understanding of why some kids go through puberty earlier or later than others. The age when puberty starts may be linked to a person’s future health.
NIEHS Clinical Research Unit
CaREFREE Study: Calorie Restriction, Environment, and Fitness: Reproductive Effects Evaluation
Women who develop irregular menstrual cycles may find it difficult to become pregnant. Researchers want to learn more about functional hypothalamic amenorrhea, an improperly performing hypothalamus in the brain, and how it can cause a woman’s period to stop temporarily. Dietary patterns and exercise may affect this function and change menstrual cycles. The CaREFREE study will look at how these factors may affect some women.
Stories from the Environmental Factor (NIEHS newsletter)
Printable Fact Sheets
Campaign Promotes Eating Safer Fish (2022) – The “Stop, Check, Enjoy!” campaign helps fishers in southeastern North Carolina understand the risks of consuming certain fish from the Cape Fear River.
Community-engaged Research Leads to Soil Cleanup (2022) – Emory University works with residents of Atlanta’s Westside community to test their urban gardening soil for lead. This effort led to awareness of health risks and the removal of lead-contaminated soil in neighborhoods.
Botanical Safety (2021) – Cynthia Rider, Ph.D., National Toxicology Program, describes how certain botanical dietary supplements may affect health and how consumers can make informed decisions.
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