Walk down the middle aisles of any American supermarket and most of what you see comes wrapped in plastic, cardboard or foil. Chips, frozen dinners, sweetened cereals and packaged snacks are designed to last for months and travel long distances. They are also the foods researchers keep linking to poorer health, for the planet and increasingly for the mind.
In the United States, ultra-processed products now make up more than half of the calories the average person eats. Nearly every one of those calories comes with a wrapper, a plastic tray or a cardboard box, a factory process and a supply chain that stretches across continents. Multiply that by three meals and a couple of snacks a day, every day of the year, and the footprint becomes enormous, both in landfills and in the way we feel.
Choosing whole, less processed food is usually framed as an environmental decision, and for good reason. Less packaging, less energy spent on factory processing and fewer miles traveled between the field and the fork. Each of those benefits is real, measurable and worth pursuing on its own, but there is a second reason to fill your cart differently. A growing body of research shows that mental health is influenced by multiple factors including your diet, and the same foods that are easier on the planet appear to be kinder to your mood.
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What ultra-processed food costs the planet
Ultra-processed foods are made mostly from refined ingredients such as starches, oils, sugars and protein isolates, combined with additives that give them color, flavor and shelf life. Producing them takes energy at every step, from cracking crops into components to reassembling them into a product.
Most of these foods come in single-use packaging, including bags, trays and pouches, often multilayer plastic that cannot be recycled in most communities. A household that relies on them sends far more waste to landfill than one that cooks from basic ingredients. Many rely on a small number of crops grown in large monocultures, which reduces biodiversity and depends heavily on synthetic fertilizer.
The alternatives are not complicated. A guide to sustainable eating usually comes back to the same principles. Eat more plants, buy local and seasonal produce where you can, choose loose goods over packaged ones and waste less of what you bring home.
What it may cost your mood
The link between diet and mental health has moved from theory to measurable evidence over the past decade. A 2024 umbrella review in The BMJ, which pooled studies covering millions of people, found that higher intake of ultra-processed food was associated with a greater risk of anxiety and common mental disorders.
Researchers are still working out the reasons. One idea is inflammation. Diets high in refined sugar and certain fats appear to raise inflammatory markers in the body, and chronic inflammation has been linked to depression. Another is the gut. The bacteria in our digestive system feed on fiber, and a diet short on whole plants starves them. Those bacteria help produce compounds that affect the brain, including many of the building blocks for serotonin.
Blood sugar also plays a part. Meals built around refined starches and sugar cause sharp spikes and dips, which many people feel as fatigue and irritability later in the day. Whole foods release energy more slowly, because their fiber slows digestion and keeps blood sugar steadier for hours.
The evidence for eating better
The strongest test so far came from a small Australian study called the SMILES trial. Adults with moderate to severe depression were coached toward a Mediterranean-style diet for 12 weeks. About a third of them reached remission, compared with fewer than one in ten in a group that received social support instead.
The diet they followed is close to what environmental groups recommend. Plenty of vegetables, fruit, legumes, whole grains, nuts and olive oil, with modest amounts of fish and far fewer processed meats, sweets and packaged snacks. Much of it can be bought loose, grown at home or found at a local market. It is a rare case where the healthiest choice for the planet and the healthiest choice for the mind line up almost exactly.
For people already being treated for depression or anxiety, diet is not a replacement for medication or therapy. It works alongside them. Some researchers are now looking at whether food choices affect how well antidepressants work, and early results suggest a better diet may support treatment rather than compete with it.
Small changes that work for both
The easiest shifts tend to reduce waste and improve meals at the same time.
Buy staples in bulk. Oats, rice, lentils, beans and nuts are cheap, filling and easy to store in glass jars. They replace a surprising number of packaged foods and cut plastic out of the kitchen.
Cook once, eat twice. A large pot of vegetable soup, chili or curry covers several meals and removes the temptation to reach for something frozen on a busy night.
Shop the edges of the store and the farmers market. Fresh produce, eggs and fish tend to come with less packaging and fewer additives. Buying what is in season usually means lower prices and better flavor. Bringing your own cloth bags and produce sacks cuts even more plastic out of the weekly shop.
Compost the scraps. Vegetable peels and coffee grounds are a sign of a whole-food kitchen, and returning them to the soil closes the loop. Even a small countertop bin feeding a backyard pile or a municipal collection program keeps food waste out of landfill, where it would otherwise release methane.
These choices fit into a wider set of preventative health habits that reduce pressure on both the healthcare system and the environment.
Anyone trying to live more sustainably already has most of the tools needed to eat for better mental health. Fewer packages, more plants and simple home cooking help the planet, and the research suggests they may help the people eating that food feel better too.