Oxidative stress occurs when your body runs out of the antioxidants required to neutralize free radicals, which are molecules that react with other substances to create abnormal cells and to damage healthy ones. You cannot completely eliminate free radicals because your body naturally creates them as it performs everyday functions, and some functions require them. However, there are ways to avoid high amounts of high radicals and to increase antioxidant intake and production to reduce oxidative stress. 
The first method is avoiding cigarette smoke whether you are smoking or around someone who smokes. Alcohol, over-the-counter and prescriptions drugs are toxins that you should avoid, as well. The fumes from chemical cleaning supplies, exhaust, and hair and nail salon products are also damaging to your health. Other toxins to avoid include chlorinated water in a pool or shower, radiation exposure and geophysical stress caused by exposure to waste dumps and powerlines.
Oxidation occurs in your body when it processes animal protein and sugar. This means that more oxidation occurs when you eat too much of these foods. Along with sugar, processed foods often contain artificial colors and flavors, and preservatives that increase oxidation. Other foods that cause oxidation include hydrogenated fats and oils that are heated to high temperatures. Eating smaller meals more frequently can help reduce oxidation.
In addition to avoiding a diet that is high in animal protein and sugar, you can eat more foods and herbs that are high in antioxidants. These foods are usually colorful, such as beets, berries, kale and tomatoes. Black and green teas, nuts and seeds are also good sources. Some high-antioxidant herbs include cinnamon, ginger and turmeric. As herbal supplements, green tea, quercetin, resveratrol and turmeric are the four best options for antioxidant support. Other useful supplements are CoQ10, selenium and vitamin C.
Your body naturally produces the powerful antioxidant glutathione, which comes from three amino acids: cysteine, glutamate and glycine. Glutathione also contains sulfur. You can boost antioxidant production by eating foods that help your body make glutathione, such as asparagus, peaches, spinach, tomatoes and walnuts. Eating high-sulfur foods such as avocados, broccoli, cabbage, collard greens, garlic, kale and onions can support glutathione production as well. You can take supplements for a boost, including those that contain alpha lipoic acid, B12, methylfolate, N-acetyl cysteine, SAMe or selenium. Other supplements that have increased glutathione production include magnesium, milk thistle, zinc and vitamins C, D and E.
Having a bacterial, fungal or viral infection triggers your immune system. This creates oxidation, which is why you have less energy when you are sick. It is important to have a plan to avoid catching a cold or infection, including sleeping for seven-and-a-half to nine hours every night and taking probiotics, vitamins A and C, and zinc to boost immune function. It is also essential that you avoid emotional, physical and psychological stress. You can achieve this by taking breaks throughout the day for enjoying nature, exercising, meditating, taking a walk, talking with a friend, watching a funny show or writing in a journal. This gives your body an opportunity to recover and allows you to recenter yourself.