Some time ago we wrote about DNA damage and how to prevent it. This time we go into deeper about the mysterious word “oxidative stress” and how to prevent it.
How to prevent oxidative stress?
Oxidative stress is caused by ROS (reactive oxygen species) which are very reactive molecules that damage our cells by reacting with all sorts of other molecules like DNA and proteins. Usually cells can hold the ROS under control with specific proteins and antioxidants. In order to supply our cells with these substances we need to eat the right foods and nourish our body accordingly (1).
Antioxidants against oxidative stress
Antioxidants hold down ROS by counteracting them. Unfortunately, antioxidant supplements have not been proven to reduce oxidative stress because many studies have had different results. Often the result may even indicate the harmfulness of antioxidant supplements. But as the relation between antioxidant levels and oxidative stress is clear (more antioxidants means less oxidative stress) and the consumption of antioxidant-rich foods like fruit and vegetables has been shown to reduce oxidative stress related problems it is safe to say that getting your antioxidants from natural food is necessary. Furthermore, the antioxidants may need other substances to function correctly like selenium and zinc which we need to get from our diet as well. The most well-known antioxidants are vitamin E, carotenoids, vitamin C, flavonoids, mannitol, riboflavin (vitamin B2), aminoguanidine, resveratrol and pyridoxine (vitamin B6) (1).
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Antioxidant rich foods
A study that measured the antioxidant levels of 119 berries and berry products, 278 fruits, 303 vegetables and other beverages gave a good overview of the foods richest in antioxidants. Some berries with especially high antioxidant levels turned out to be dried amla (Indian gooseberry, 261.5 mmol/100 g), wild dried dog rose (Rosa canina), dried wild bilberries (from Northern Europe), zereshk (red sour berries) and fresh dog rose. Other examples of antioxidant rich berries are fresh crowberries, black currants, wild strawberries, blackberries, goji berries, sea buckthorn and cranberries. Unsurprisingly the berry products with the lowest level of antioxidants are some of the berry jams with mean values of 0.5 mmol/100 g.
They found that antioxidant rich fruits and vegetables are dried apples, flour made of okra, artichokes, lemon skin, dried plums, dried apricots, curly kale, red and green chili and prunes. Interestingly, the highest level of antioxidants from all food groups is found in herbs. Sangre de Grado (Dragon’s Blood) from Peru has the highest antioxidant content of all the products in this study`s database (2897.1 mmol/100 g).
As has been shown before, the level of antioxidants is much higher in plant-based foods and lower in animal-based foods like meat and dairy (2). This is due to the high ROS levels from photosynthesis in plants that they need to protect themselves from with antioxidants (3). For all of the results go to downloadable PDF.
Sources of main antioxidants
|Antioxidant||Foods containing high levels of antioxidant|
|Vitamin C||Fresh or frozen fruits and vegetables|
|Vitamin E||Vegetable oils, nuts, and seeds|
|Resveratrol||Grape skin, nuts and berries (4)|
|Flavonoids||Leafy vegetables and onions (5)|
|Pyridoxine (Vitamin B6)||Fish, beef, liver, starchy vegetables, and fruit|
|Riboflavin (vitamin B2)||Eggs, green vegetables, milk (6)|
|Vitamin A||Fruit, vegetables and eggs|
1. Moreira, P. L., Villas Boas, P. J. F. & Ferreira, A. L. A. Association between oxidative stress and nutritional status in the elderly. Rev Assoc Med Bras (1992) 60, 75–83 (2014).
2. Carlsen, M. H. et al. The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide. Nutr J 9, 3 (2010).
3. Foyer, C. H. & Shigeoka, S. Understanding Oxidative Stress and Antioxidant Functions to Enhance Photosynthesis. Plant Physiology 155, 93–100 (2011).
4. Wojcik, M., Burzynska-Pedziwiatr, I. & Wozniak, L. A. A review of natural and synthetic antioxidants important for health and longevity. Curr. Med. Chem. 17, 3262–3288 (2010).
5. Woo, H. D. et al. Dietary Flavonoids and Gastric Cancer Risk in a Korean Population. Nutrients 6, 4961–4973 (2014).
6. Office of Dietary Supplements – Riboflavin. Available at: https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/. (Accessed: 18th July 2018)
7. Medicine, I. of. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. (1998). doi:10.17226/6015
8. Korać, R. R. & Khambholja, K. M. Potential of herbs in skin protection from ultraviolet radiation. Pharmacogn Rev 5, 164–173 (2011).
9. Kaur, C. D. & Saraf, S. In vitro sun protection factor determination of herbal oils used in cosmetics. Pharmacognosy Res 2, 22–25 (2010).
10. Gause, S. & Chauhan, A. UV-blocking potential of oils and juices. Int J Cosmet Sci 38, 354–363 (2016).