Plants are prolific chemical factories. They continuously produce thousands of compounds called phytochemicals. These chemicals perform vital functions for the plants, and some are noxious or even poisonous. But some plant chemicals are helpful to humans when consumed in foods, such as fruits, vegetables, plant oils, and whole grains. Perhaps not surprisingly, these same foods are part of the healthy eating pattern outlined in the 2015-2020 Dietary Guidelines for Americans. Part of the reason why eating patterns based on whole foods are healthy may be their anti-inflammatory properties.
Anti-inflammatory diets purport to protect cells and organs from low-level, chronic inflammation, which some studies have linked to heart disease, cancer, arthritis, and other common health conditions. Researchers are working to establish whether eating a diet containing anti-inflammatory phytochemicals prevents such diseases and their burden of premature death and disability. But dietitians don’t yet have a diet based on clinical evidence, definitively showing that foods with certain phytochemicals prevent or treat diseases—akin to the DASH diet, shown to lower high blood pressure.
“The problem is we don’t have enough research on this to really have a template for an anti-inflammatory diet,” says Alicia Romano, MS, RD, LDN, Registered Dietitian, Frances Stern Nutrition Center, Tufts Medical Center. “I would describe it as more a model of eating. It means selecting foods that may have anti-inflammatory properties in nature.”
Good and Bad Inflammation: Inflammation is not inherently a bad thing—far from it. Short-lived, or acute, inflammation is part of the body’s healing response to injury, toxins, and infection. Damaged cells release chemicals that allow blood vessels to leak fluid into the tissues, causing swelling that may help to isolate the damage from the surrounding tissues. The immune system dispatches special cells to target invaders like bacteria and eliminate the damaged cells.
Some research has tied persistent, low-level inflammation to a variety of health problems. “These are the chronic diseases that we’re most worried about, like heart disease, cancer, and arthritis, and diabetes, and maybe even the non-Alzheimer’s vascular dementias,” says Jeffrey B. Blumberg, PhD, Tufts professor and senior scientist at the HNRCA Antioxidants Research Laboratory.
However, proving that eating anti-inflammatory foods prevents specific diseases remains a challenge, and the jury is still out. The search for new and better evidence on these questions is concerted and ongoing.
In studies, chronic inflammation can be measured in the “footprints” of inflammation, such as the levels of certain telltale chemicals circulating in the blood called biomarkers. Biomarkers commonly used in studies are C-reactive protein (CRP) and proteins released by the immune system, called cytokines.
Taking in anti-inflammatory phytochemicals is associated with lower levels of CRP and other inflammatory biomarkers. But this correlation doesn’t necessarily prove that anti-inflammatory diets prevent diseases or relieve their symptoms. Inflammation itself could be a symptom—not the underlying cause—of a given health problem.
“Chronic, low-level inflammation can be modulated by diet—I don’t think that’s hugely controversial,” Blumberg says. “The controversial part is this: If I eat an anti-inflammatory diet, will it reduce my risk for all these chronic diseases?”
Phytochemicals and Foods: If you want to try an anti-inflammatory diet, where do you start? Blumberg stresses that “anti-inflammatory” refers to the underlying biological mechanism, not the foods themselves. “It is important to talk about anti-inflammatory foods rather than specific anti-inflammatory nutrients.”
“Essentially this diet really focuses on whole plant-based foods that are rich in healthy fats and phytochemicals,” Romano says. “The idea is to get as much nutritional punch in everything that we’re eating to potentially achieve the beneficial effect that these foods offer.”
Anti-inflammatory foods are the ones you are already advised to eat for optimal health. “These include whole grains, which are very rich in phytochemicals,” Blumberg says. “Beans, nuts, herbs, and spices are filled with anti-inflammatory compounds called flavonoids and related compounds. Fiber is another part of anti-inflammation, and of course fruits, vegetables, and the omega-3 fatty acids in fish. Anti-inflammatory diets really have some merit but, on the other hand, they’re not magical panaceas.”