Most of us have heard of ‘antioxidants’ and know that they should be included in a healthy diet, however exactly what they are and why we need them is a little less clear...
The body has its own inbuilt system of antioxidants; however, research indicates that antioxidants consumed through the diet can reduce damage to cells and tissues within the body and therefore help prevent illness.
Before looking at what antioxidants are, it is first important to understand what a free radical is. These are highly reactive compounds that are created in the body during normal metabolic functions, or introduced from our environment.
Free radicals are inherently unstable and very reactive, meaning that they contain ‘extra’ energy which they try to reduce by reacting with certain chemicals within the body. This can then interfere with our cells' ability to function normally, leading to a multitude of health problems.
Where do free radicals come from?
Free radicals can either occur naturally in the body or come from sources outside the body. Processes in the body that can produce free radicals include energy production, immune system activity, breaking down fatty acids and detoxification.
Exogenous sources (from outside the body) include:
- Ionising radiation (x-rays, higher UV lights, gamma rays, rays from electronic devices)
- Car exhausts, cigarette smoke1
- Xenobiotics (chemicals and drugs)
- Excessive alcohol
- Excessive exercise
- Heavy metal2
- Fats in the diet
From a nutritional perspective, paying attention to which fats you are consuming will impact the level of free radicals in your body. There are concerns about diets with high levels of polyunsaturated fats, which can oxidise and generate free radicals3.
Polyunsaturated fats found in seed oils such as sunflower oil, canola oil and peanut oil are very susceptible to damage from heat, light and oxygen. For example, seed oils can become oxidised when used for frying at high temperatures, or left out of the fridge in a clear bottle either in the supermarket or at home.
But what does ‘oxidized’ mean and why is it bad?
To put it very simply, oxidation means that molecules in your body will lose part of themselves (electrons), and therefore become unstable and reactive while they look for something to fill the space that the electron has left. The molecule has become a free radical, lost a part of itself, and is essentially looking for something to fill this void.
Research has found that oxidisation of vegetable oils led to the release of high concentrations of chemicals called aldehydes, which have been linked to illnesses including cancer, heart disease and dementia4.
Excessive or extreme exercise can be a highly oxidative process and produce free radicals. The free radicals produced during exercise are released during the processes in the body that create energy. Although moderate exercise has been shown to be beneficial for health, research indicates that high-intensity activity can incite free radical production because of the increased demands on your cells to produce energy, as well as the activation of bodily processes through tissue injury and inflammation5.
What do free radicals do to the body?
Free radical reactions occur in most human diseases and excessive amounts can damage cells and tissues in the body. This is not to say that free radicals are the cause of most diseases, but they are believed to play a role in more than 60 different health conditions; ranging from heart disease, arthritis, cancer, Alzheimer’s, Parkinson’s and diabetes6.
There is research that proposes ageing as the cumulative result of oxidative damage to the cells and tissues of the body. There is some interesting science behind this, however many uncertainties concerning the role of oxidative damage in ageing remain.7
Research is ongoing so it is definitely not a theory to be ruled out altogether, however, ageing should be viewed as a multifactorial process, involving a variety of lifestyle factors.
Antioxidants are compounds that prevent oxidative damage in biological systems and ‘mop up’ free radicals. The body has its own inbuilt system of antioxidants but we can also consume them through our diet.
The key antioxidants work synergistically and when combined can enhance the activity of each other so it is important to include a variety of antioxidants in your diet.
Plants contain their own integrated antioxidant systems to protect their own cellular components from free radical damage, so fruits and vegetables are an excellent source of antioxidants.
Plants contain a group of antioxidants called phytochemicals or phytonutrients, which are responsible for the colour and taste of different fruit and vegetables. This is why it is important to include an array of colourful fruit and vegetables into your diet, so you are exposed to as many antioxidants as possible.
What are the key antioxidants and where can I find them?
- Beta-carotene – red/orange/yellow fruit and vegetables
- Lycopene – tomatoes
- Lutein – kale, spinach, chard, courgette, Brussel sprouts, broccoli
- Vitamin C – red peppers, oranges, kale, strawberries
- Vitamin E – almonds, sweet potato, avocado, sunflower seeds
- Selenium – Tuna, mushrooms, herring, oysters
- Zinc – Ginger root, lamb, pecan nuts, oysters
- Bioflavanoids – citrus fruits
- Anthocyanidins and proanthocyanidins – berries, grapes
- Curcumin – turmeric
What can I do to protect against free radical damage?
Reduce, stop or limit:
- Stress levels
- Excessive alcohol consumption
- Excessive exposure to sunlight (UV Radiation) and exposure to x-rays
- Exposure to industrial chemicals or polluted environments
- Excessive exercise
- Consumption of convenience foods
- Consumption of a variety of fresh fruit and vegetables
- Eat as many varied natural colours as possible
- Sleep and relaxation
- Moderate exercise
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