Introduction to antioxidants


Our bodies are extraordinarily complex and are perpetually engaged in internal processes of metabolism to keep us alive. These processes create what are known as free radicals that can cause oxidative stress. In addition, we subject ourselves to a host of environmental circumstances that produce free radicals, such as too much sun exposure, tobacco smoke, deep fried foods, pollution, alcohol, stress, and sugar.


A free radical is an atom or molecule that has an unpaired electron. Oxygen is a highly reactive element that steals electrons from stable molecules and can start a chain reaction of free radicals. This is known as oxidation and it causes the cell damage that can lead to inflammation and diseases such as diabetes, dementia, cardiovascular disease, cancer, cataracts and more. It’s also believed to contribute to accelerated aging. Things such as our DNA, fatty acids, and cellular tissue are vulnerable. We know oxygen is critical to life, which means that free radicals and oxidation are a part of life. Their occurrence is as important as they are damaging.  Our bodies use free radicals in a controlled fashion to kill unwelcome microbial organisms. It is important that we give our bodies the tools to control free radicals as needed; it is a delicate balance.  It should come as no surprise that we maintain the balance, in part, by consuming antioxidants in our daily diet.


Once we understand free radicals, understanding antioxidants is easy. Basically, antioxidants neutralize free radicals by providing electrons thereby terminating the chain reaction that can lead to inflammation and other damage. Ideally one gets antioxidants from the foods they consume and not from supplements.

L-Ascorbic Acid

VITAMIN C as an antioxidant: Vitamin C is a water-soluble vitamin also known as ascorbic acid. Unlike most mammals, humans cannot biologically manufacture Vitamin C, and we must get it from our diet. Vitamin C is important for a number of processes to maintain good health and not just as an antioxidant. Fortunately, there are many sources, including sweet peppers, broccoli, Brussels sprouts, citrus, white potatoes, parsley, kiwi fruit, strawberries, and tomatoes, to name a few. Because it is easily damaged by high heat and time, it’s best to eat these foods soon after picked or purchased. It helps when cooking to do it quickly such as stir frying or microwaving. Buying frozen vegetables instead of fresh can ensure a better source of some nutrients, including Vitamin C. Although it is important to know about the volatility of Vitamin C, simply eating a good variety of plant based foods will ensure you are getting adequate amounts. Supplements can be used, but if you’re healthy and eating a good diet, then supplements are unnecessary. Toxicity is not common with Vitamin C, but if supplementation is desired, it’s ideal to limit it to the RDA of 90 mg/day for men and 75 mg/day for women with an upper limit of 2,000 mg/day and/or under the advisement of a healthcare professional.

VITAMIN E as an antioxidant: Vitamin E is known as α-tocopherol in its natural and biologically preferential form. Although there are many forms that may prove beneficial, this form is the predominant form in human biology. It is a fat-soluble vitamin and is known primarily for its antioxidant properties in lipids (fats and cholesterol). It has an important role to protect the lipids in the cell walls and is thought to facilitate the adaptive immune system and improve cell communication.  Vitamin E prevents the oxidation of the lipid LDL cholesterol, which when oxidized is known to cause cardiovascular damage and heart disease. The best dietary sources of Vitamin E are unsaturated vegetable oils (soybean, safflower, corn, olive, canola, etc.), nuts, nut butters, seeds, avocados, greens, and wheat germ/wheat germ oil. Vitamin E is fairly stable in heat and light, but in the presence of oxygen, it oxidizes more rapidly, such as in deep-frying. In the body, Vitamin C is known to replenish the antioxidant properties of Vitamin E. The adult RDA for Vitamin E is 15 mg/day with an upper limit of 1,000 mg. Like Vitamin C, there is usually enough Vitamin E in a balanced diet that one doesn’t need supplements. Excessive supplementation can encourage bleeding and may interfere with the absorption of vitamins A and K, which are also fat soluble vitamins.

Vitamin E and Vitamin C are two known powerful antioxidants, but there are others. At the very least they include selenium, Vitamin A, the carotenoid family (Β-carotene, α-carotene, lycopene, lutein, Β-cryptoxanthin, and zeaxanthin) and a multitude of other phytochemicals. Science is still researching and learning about many of the phytochemicals and their functions. Phytochemicals are found in abundance in colorful fruits and vegetables, coffee, tea, herbs and spices. When it comes to getting the most from antioxidants in food, the recommendation remains the same: eat a healthy and balanced diet each day with a focus on minimally processed foods, fruit, vegetables, healthy fats, lean proteins, and whole grains.

Significance of Nutrition to the Immune System

Our bodies make excellent homes for other living organisms, so it is important that we have a way to protect ourselves when these extraneous organisms threaten our health.  This is why we have an immune system. The immune system is complex and has a number of working parts that make it very effective in managing harmful organisms, but it can also cause a great deal of damage if we don’t take care of our bodies.

So, how do we take the best care of our body and our immune system? We should eat a good diet, get adequate sleep, exercise daily, manage stress and don’t smoke. If these sound familiar, it’s because they are the same recommendations for the optimal function of every system in our body.

When it comes to what we put in our body, the nutrition recommendations to eat a variety of fruits and vegetables in combination with lean meats, plant-based proteins, whole grains, and healthy fats should also sound familiar. Most of us have heard the warnings to avoid processed foods, saturated fats, trans fats, and excess amounts of added sugar.  As well researched as all of this advice is, there are obstacles to following it. For instance, the discovery of preservatives has made processed foods cheap and readily available. Suddenly we find that fresh food takes more effort to obtain and prepare than processed foods.  Adding insult to injury, the ability of manufacturers to alter food for a longer shelf life means they can also alter foods to appeal to our baser senses, including our inclination for sweets or for deep fried and/or salty foods. Eating these highly processed products regularly reduces the intake of the whole unprocessed foods that protect us from damage. They cause a constant stimulation of the immune system, also known as inflammation. Chronic inflammation then quietly leads to heart disease, kidney disease, dementia, and diabetes, among other undesirable outcomes.

So, let’s look at nutrients specific to the immune system:

  • Vitamin C – can be found in most fruits and vegetables. Citrus, sweet peppers, kiwi, leafy greens, tomatoes are foods high in Vitamin C, but there are many more.
  • Vitamin A – orange vegetables are orange because of their beta-carotene content. Beta-carotene is a precursor for Vitamin A and readily converted to Vitamin A in the body.  Vitamin A is stored in the liver, which means animal liver is the best source of the vitamin itself.
  • Vitamin E – nuts, nut butters, plant based oils, whole grains and wheat germ
  • Vitamin D – sunlight exposure (without sunblock), fortified milk, mushrooms that have been exposed to the sunlight and fatty fish. Vitamin D can be difficult to get in the diet and may benefit from supplements, especially in older adults.
  • Zinc – red meat and poultry, whole grains, oysters, nuts and legumes
  • Selenium – meat, nuts and leafy greens. One doesn’t need much selenium and many foods contain it.
  • Probiotics – feed your gut bacteria with prebiotics, which includes high fiber foods, fruits and vegetables, whole grains and avoiding large portions of animal products.  You can add probiotics with yogurt and fermented foods.
  • Omega 3 – high fat fish, walnuts, flax seeds

This list is not a complete dietary profile of nutrients, instead, its focused on immune function. There are significant things to point out that the reader may have noticed:

  1. Variety in diet plays a big role in health and sustainability.
  2. There is little mention of processed foods in the lists, although some minimally processed foods can be good. Go beyond the front of the package and read ingredient and nutrition labels and then assess its value.
  3. With the exception of Vitamin D, there was no mention of supplements. Some people may have a need for supplementation, but supplements shouldn’t be considered a replacement for food. Foods act symbiotically with the nutrients both within the food and in concert with other foods. Supplements cannot duplicate this. We have to eat to live so why not eat foods that benefit us?

We are not always aware of the damage our immune system is causing through inflammation, and if you feel concerned enough that you want to eat even a little better to prevent or reduce inflammation, it’s not that hard to do. Knowing what’s best for our bodies doesn’t make us do it, so be conscious and aware of what you put into your body; make small changes and after a while, the more unhealthy foods you used to love won’t play the same role anymore. You may lose your taste for them, or you will savor them more when you eat them. Committing to a good diet doesn’t mean giving up all the foods you love. It means changing the way you eat them.