What Foods Cause Oxidative Stress?

Oxidative stress is a common condition that can cause a surprisingly large number of health issues that include inflammation heart disease, diabetes, and even cancer.

Diet plays an essential role in health, as the food you eat provides the fuel and nutrients your cells, tissues, and organs need to function well. Food also helps you manage oxidative stress, which is a natural process that can negatively affect your health. In fact, some foods can actually cause oxidative stress in ways that lead to health problems.

What are the Main Causes of Oxidative Stress?

Oxidative stress develops when you have too many free radicals — unstable atoms or molecules that damage other atoms and molecules.

In a process known as oxidation, your body cells use oxygen to break down food molecules for energy. The metabolic process of breaking down food can cause some atoms to lose electrons, which are negatively-charged particles that balance the positively-charged protons. Losing electrons causes the atoms and molecules to become unstable; scientists refer to these unstable molecules as free radicals.

Free radicals try to stabilize themselves by stealing electrons from other atoms. This has a domino effect in that taking electrons away from stable atoms creates even more free radicals. As the number of free radicals grows, the more unstable cells, organs, and tissues become.

Some free radicals, known as reactive oxygen species (ROS), contain oxygen atoms. These free radicals can damage DNA, proteins, and body fats.

The human body produces antioxidants that help keep the body balanced by providing free radicals with the electrons they need, but without becoming free radicals themselves. Unfortunately, the body cannot always produce enough antioxidants to keep free radicals in check, and this can cause an unhealthy unbalance of free radicals and antioxidants.

The free radicals can outnumber antioxidants in a condition that scientists refer to as oxidative stress. Left unaddressed, oxidative stress can disrupt body systems to cause ill health.

External factors, such as exposure to pollution or toxic pesticides, can trigger the development of free radicals and cause oxidative stress. Certain foods can also influence the balance of free radicals and antioxidants naturally.

What Food Causes Oxidative Stress?

Some foods contribute to oxidative stress by either causing the production of free radicals or by reducing antioxidants – or both. The key to good health is knowing which foods cause oxidative stress.

The following are examples of foods high in free radicals:

Easily-oxidized fats and oils

Some oils oxidize more easily than do others and these same oils tend to be overconsumed, both of which can lead to oxidative stress.

To reduce exposure to oxidized fats and oils:

• Do not re-use cooking oil more than a few times
• Use low smoke point oil (like extra virgin olive oil) for high temperature (over 400 degrees) cooking
• Store oils away from heat sources in closed, dark containers
• Only eat deep-fried foods occasionally, if at all
• Avoid eating excessive amounts of fat

Refined carbohydrates

The body breaks down sugars and starches, which are carbohydrates, to use as fuel. The action of breaking down carbohydrates can create free radicals as a byproduct. Eating a diet high in sugars and starches shifts the production of free radicals into overdrive, thereby creating oxidative stress. Evidence suggests that refined carbs, in particular, may lead to more oxidative stress and inflammation. These processed carbs have been stripped of fiber and other nutrients and are best kept to a minimum in a healthy diet.

Here are some refined carbs to eat in moderation:

• Pancakes
• Soft pretzels
• Bread products
• Ice cream and milkshakes
• Microwave popcorn
• Spaghetti
• Soft drinks
• Candy

Processed meat

The preservatives in processed meat may also contain free radicals. Processed meat includes:

• Sausages
• Bacon
• Ham
• Pepperoni
• Hot dogs
• Salami
• Corned beef
• Many deli meats

Alcohol

Alcohol increases the production of reactive oxygen species, reduces the level of antioxidants present in cells, and enhances oxidative stress in many body tissues, especially in the liver.

Foods that Improve Oxidative Stress

Some foods can improve oxidative stress because they contain vitamins, minerals, and chemicals that introduce antioxidants into the body. Antioxidant-rich foods include fruits and vegetables, whole grains, nuts and seeds, and spices. Cocoa, tea, and coffee also contain antioxidants that fight oxidative stress.

Vitamin C

Many fresh fruits and vegetables contain vitamin C, which is a potent antioxidant. These foods include: Broccoli, Brussels sprouts, cauliflower, cantaloupe, leafy greens, grapefruit, honeydew, kale, lemon, kiwi, orange, snow peas, papaya, sweet potato, strawberries, tomatoes, and bell peppers.

Vitamin E

Vitamin E is a power antioxidant that fights oxidative stress. To get the vitamin E you need, eat plenty of avocados, almonds, Swiss chard, red peppers, leafy greens, peanuts, boiled spinach, and sunflower seeds.

Carotenoids

Carotenoids give plants their color, but they are also antioxidants. Beta-carotene is a carotenoid that gives carrots their orange color, for example, and lycopene makes tomatoes and pink grapefruit red. Other foods rich in carotenoids include apricots, asparagus beets, cantaloupe, watermelons, and bell peppers. Look for brightly-colored fruits and vegetables, and always eat a rainbow of food.

Selenium

Selenium is a trace mineral found in Brazil nuts, shellfish, fish, beef, poultry, brown rice, and barley.

Zinc

Zinc is an essential mineral in beef and poultry, shrimp, oysters, pumpkin seeds, sesame seeds, lentils, chickpeas, cashews, and fortified cereals.

Phenolic compounds

Phenolic compounds help plants resist stress; they can also help humans fight oxidative stress. Several types of phenolic compounds exist in food, including:

• Quercetin in apples, red wine, and onions
• Catechins in tea, cocoa, and berries
• Resveratrol in red and white wine, grapes, peanuts, and berries
• Coumaric acid in spices and berries
• Anthocyanins in blueberries and strawberries

Consult with your healthcare or wellness professional for more information on what foods cause oxidative stress and foods that improve oxidative stress. Avoiding foods high in free radicals can help you lead a healthier life.

This article was originally published on November 14, 2022, and was last updated on August 9, 2024.