Eating fresh strawberries boosts red blood cells

12 July 2011

Eating strawberries for two weeks can improve the antioxidant capacity of blood and the ability of the body to protect itself from a range of diseases and physiological stresses.

Scientists have previously tried to confirm the antioxidant capacity of strawberries using in vitro laboratory experiments. Now, a team of researchers from the Marche Polytechnic University (UNIVPM, in Italy) and the University of Granada (UGR, in Spain) have demonstrated this effect in vivo, in a study on human volunteers.

In the study [1], a group of volunteers ate half a kilo of strawberries every day for two weeks. Each day, the scientists fed 12 healthy volunteers 500 grams of strawberries (of the 'Sveva' variety) over the course of the day. They took blood samples from them after four, eight, 12 and 16 days, and also a month later. The results show that regular consumption of strawberries can improve the antioxidant capacity of blood plasma and also the resistance of red blood cells to oxidative haemolysis (fragmentation).

"We have shown that some varieties of strawberries make erythrocytes more resistant to oxidative stress. This could be of great significance if you take into account that this phenomenon can lead to serious diseases", said Maurizio Battino, lead author of the study and a researcher at the UNIVPM.

The team is now analysing the variations caused by eating smaller quantities of strawberries (average consumption tends to be a 150g or 200g bowl per day). "The important thing is that strawberries should form a part of people's healthy and balanced diet, as one of their five daily portions of fruit and vegetables", Battino points out.

Professor Battino told MTB Europe that the antioxidative capacity of strawberries remains higher than other fruit after processing such as freezing or jam making. In a previous study [2] he reviewed the range of bioactive compounds in berries that are relevant to human health. These include several antioxidants, such as vitamin C, polyphenols, anthocyanins, which are present in different amounts in different fruits and vary with environmental and genetic factors.

The search for the most antioxidant variety

"Various strawberry varieties are also being analysed in the laboratory, since they each contain antioxidants in differing amounts and proportions", explains José Luis Quiles, the Spanish participant in the study and a researcher at the UGR.

The body has an extensive arsenal of very diverse antioxidant mechanisms, which act at different levels. These can be cellular tools that repair oxidised genetic material, or molecules that are either manufactured by the body itself or consumed through the diet, which neutralise free radicals. Strawberries contain a large amount of phenolic compounds, such as flavonoids, which have antioxidant properties.

These substances reduce oxidative stress, an imbalance that occurs in certain pathologies, (such as cardiovascular disease, cancer and diabetes) and physiological situations (birth, ageing, physical exercise), as well as in the battles between "reactive kinds of oxygen" — in particular free radicals — and the body's antioxidant defences.

When the level of oxidation exceeds these antioxidant defences, oxidative stress occurs. Aside from causing certain illnesses, this is also implicated in phenomena such as the speed at which we may age, for example.

References

1. Sara Tulipani, José M. Álvarez-Suarez, Franco Busco, Stefano Bompadre, José L. Quiles, Bruno Mezzetti , Maurizio Battino. "Strawberry consumption improves plasma antioxidant status and erythrocyte resistance to oxidative haemolysis in humans". Food Chemistry 128 (1): 180-186, September 2011 (available on line 9 March 2011). Doi:10.1016/j.foodchem.2011.03.025.

2. Maurizio Battino, Jules Beekwilder, Beatrice Denoyes-Rothan, Margit Laimer, Gordon J McDougall, and Bruno Mezzetti. Bioactive compounds in berries relevant to human health. Nutrition Reviews, Vol. 67(Suppl. 1):S145–S150. doi:10.1111/j.1753-4887.2009.00178.x
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