The foods most worth avoiding are ultra-processed products, processed meats, items high in added sugar, and a handful of fish species contaminated with mercury. These aren’t obscure ingredients. They’re staples in most grocery stores and restaurants, and the research connecting them to serious health problems is strong. A 2024 umbrella review in The BMJ found direct links between ultra-processed food consumption and 32 different negative health outcomes, spanning heart disease, cancer, diabetes, and mental health conditions.
Ultra-Processed Foods
Ultra-processed foods are industrial formulations made primarily from chemically modified substances extracted from whole foods, combined with additives that enhance taste, texture, appearance, and shelf life. They contain minimal to no intact whole foods. Think packaged snacks, carbonated soft drinks, instant noodles, and ready-made frozen meals.
The health risks here aren’t subtle. Convincing evidence, the highest tier in research classification, links ultra-processed food consumption to cardiovascular disease death and type 2 diabetes. The same level of evidence connects these foods to anxiety and common mental health disorders. Beyond those top-tier findings, associations extend to cancer, respiratory problems, and gastrointestinal issues. The pattern is consistent across dozens of studies involving millions of people.
Identifying ultra-processed foods at the store is straightforward: flip the package over. If the ingredient list includes substances you wouldn’t find in a home kitchen (emulsifiers, flavor enhancers, hydrogenated oils, high-fructose corn syrup), it qualifies. A good rule of thumb is that the longer and more unfamiliar the ingredient list, the more processed the product.
Processed and Cured Meats
Processed meats like bacon, hot dogs, sausages, deli slices, and jerky carry one of the clearest dietary risk signals in nutrition science. The International Agency for Research on Cancer classifies processed meat as a Group 1 carcinogen, the same category as tobacco smoking. Each 50-gram daily portion (roughly two slices of deli meat or one hot dog) increases colorectal cancer risk by 18%.
If you’ve noticed labels advertising “no added nitrites” or “cured with celery powder,” don’t assume those products are safer. Celery powder is used precisely because it’s naturally high in nitrates, which convert to the same compounds as synthetic sodium nitrite during processing. Studies show that sausages made with celery powder produce similar chemical profiles to those made with traditional curing agents, including comparable residual nitrite levels. The label looks cleaner, but the chemistry is essentially the same.
Foods Loaded With Added Sugar
The American Heart Association recommends no more than 36 grams (9 teaspoons) of added sugar per day for men and 25 grams (6 teaspoons) for women. A single can of soda typically contains 39 grams, blowing past both limits in one sitting. Beyond sodas, added sugar hides in flavored yogurts, granola bars, pasta sauces, breakfast cereals, and sweetened coffees.
Excess added sugar drives insulin resistance, weight gain, fatty liver disease, and chronic inflammation. It’s also one of the primary reasons “low-fat” products can be worse than their regular counterparts. When manufacturers remove fat, they frequently replace it with sugar to maintain flavor. A systematic comparison found that low-fat and non-fat versions of foods across every major category (dairy, baked goods, meats, salad dressings) contain significantly more sugar than regular versions. The differences are sometimes dramatic: regular Caesar dressing contains about 2.8 grams of sugar per tablespoon, while the non-fat version contains over 30 grams. Non-fat cheddar cheese has more than five times the sugar of regular cheddar. Non-fat sour cream has roughly double the sugar of full-fat. Choosing the “healthier” option based on a low-fat label often means trading one problem for another.
High-Mercury Fish
Fish is generally one of the healthiest protein sources available, but a few species accumulate dangerous levels of mercury. The FDA maintains a specific avoidance list for seven types of fish with the highest mercury concentrations:
- King mackerel
- Marlin
- Orange roughy
- Shark
- Swordfish
- Tilefish (from the Gulf of Mexico)
- Bigeye tuna
Mercury accumulates in the body over time and damages the nervous system, making these fish particularly risky for pregnant women, nursing mothers, and young children. Note that bigeye tuna is the specific variety to avoid. Canned light tuna and skipjack tuna have much lower mercury levels and are considered safe in moderate amounts.
Foods High in Hidden Sodium
More than 70% of the sodium Americans consume comes from packaged and restaurant foods, not the salt shaker at home. The biggest culprits are canned soups, deli and lunch meats, frozen dinners, pizza, bread, and restaurant meals in general. A single serving of canned soup can contain half your daily recommended sodium intake without tasting particularly salty.
Excess sodium raises blood pressure, which over time increases the risk of heart attack and stroke. Because so much sodium is embedded in processed and prepared foods, the most effective strategy is cooking more meals from whole ingredients rather than trying to track sodium across dozens of packaged products.
Foods Still Containing Trans Fats
Partially hydrogenated oils, the primary source of artificial trans fats, have been largely banned in the United States since 2018. But trans fats haven’t disappeared entirely. The ban didn’t cover foods sold without nutrition labels, including items from bakeries, cafeterias, school kitchens, and many restaurants. Deep-fried foods at restaurants remain a common source, since some establishments still use partially hydrogenated oils in their fryers. Commercially prepared baked goods like cookies, pies, and donuts may also contain them.
Trans fats raise your “bad” cholesterol while lowering your “good” cholesterol simultaneously, making them uniquely harmful to cardiovascular health. When eating out, avoiding deep-fried foods and commercial desserts is the most practical way to limit exposure. At home, check ingredient lists for “partially hydrogenated” anything, even if the nutrition label shows 0 grams of trans fat (manufacturers can round down from up to 0.5 grams per serving).
Refined Grains and Blood Sugar
White bread, white rice, pastries, and most packaged cereals are made from grains stripped of their fiber-rich outer layers. The key issue is how your body processes them: without fiber to slow digestion, refined grains cause faster, higher spikes in blood sugar.
The difference matters most with rice. A meta-analysis of controlled trials found that whole-grain rice significantly reduces the blood sugar spike after a meal compared to white rice. Interestingly, the same clear benefit didn’t show up when comparing wholemeal wheat flour to white wheat flour, likely because grinding whole wheat into fine flour breaks down the grain structure enough to negate much of the advantage. The takeaway: intact whole grains (brown rice, steel-cut oats, farro, quinoa) offer the most benefit. Simply buying bread labeled “whole wheat” may not produce the blood sugar improvements you’d expect if the grain has been finely milled.
Artificial Sweeteners: Caution, Not Panic
In 2023, the WHO’s cancer research agency classified aspartame as “possibly carcinogenic to humans,” based on limited evidence linking it to liver cancer. That sounds alarming, but “possibly carcinogenic” is the agency’s third tier out of four, and it shares that category with things like aloe vera and pickled vegetables. At the same time, the joint WHO/FAO expert committee on food additives reaffirmed that aspartame is safe within established daily limits of 40 milligrams per kilogram of body weight. For a 150-pound person, that’s roughly 12 cans of diet soda per day.
The practical concern with artificial sweeteners isn’t cancer risk at normal consumption levels. It’s that diet sodas and zero-calorie sweetened products often travel alongside poor overall dietary patterns, and some research suggests they may affect appetite signaling and gut bacteria in ways that aren’t fully understood yet. If you’re choosing between a regular soda with 39 grams of sugar and a diet version, the diet option is almost certainly the lesser harm. But water remains the simplest choice you don’t have to think twice about.