Background

We have probably all been told at some point to ‘eat up our vegetables’ because they are good for us. While we may not have believed it at the time, there’s now a lot of work to suggest that Mum may have been right on this point. Fresh fruit and vegetables are a good source of antioxidants, and it is these antioxidants which are now thought to help to prevent illnesses such as cardiovascular disease and cancer. For those who do not care for vegetables, the news that red wine was a good source of antioxidants was very welcome! In fact, this message seems to have got across to the consumer quite well and its a popular perception now that red wine is good for your health.

But what are antioxidants and why should they be good for you? Antioxidants can be many different compounds but they all share the property that they are able to quench, or neutralise free radicals. In theory, the more antioxidants in your cells, the less free radicals. This is important because its free radicals themselves which are suspected to be involved with starting cancers and speeding up the progression of cardiovascular disease.

Antioxidants in cider

For the health conscious consumer who needs a break from the Bordeaux, there’s other options. Any beverage made from fresh fruit or vegetables is likely to have antioxidants - take cider for example. Cider is made from apples, and apples contain an abundance of antioxidants such as quercetin in the apple peel and hydroxycinnamic acids. Not surprisingly, apple juice and cider also contain antioxidants. In a joint project with the Institute of Food Research at Norwich we measured the amount of antioxidants in 18 UK ciders. To do this, some of the cider was added to a solution containing free radicals and then the amount of free radicals knocked out by the beverage was measured. This simple lab-based test comes up with a ‘score’ for that particular cider. In our study, we found that the antioxidant activity score for ciders ranged between 100 and 2595 units for a 250 ml serving.

How good is this score for ciders? It is in fact very good. The beauty of this method of measuring antioxidant activity is that it can be used to compare scores for foods and beverages in other studies. For example, looking at the table below its clear that cider is one of the top choices for antioxidant content!

 

Antioxidant activities of selected foods and beverages

From Paganga et al (1999)

*BRI/IFR project data

Source	Portion size	Antioxidant activity (mmol Trolox equivalents)
Apple (peled)	100g	640
Tomato	100g	160
Aubergine	100g	490
Onion	100g	580
Red wine (Rioja-Bordeaux)	150ml	2100-3400
White wine	150ml	220
Black Tea (0.25%)	150ml	1400
Green Tea (0.25%)	150ml	1350
Cider*	250ml	100-2595
Apple juice (long life)	150ml	140
Orange juice	150ml	400
Blackcurrant juice	150ml	800

So for consumers who enjoy an occasional glass of cider in the evening or down the pub, they can rest assured that they are also getting a pretty healthy dose of antioxidants!

Bioavailablity

Although this sounds straightforward, life is never that easy. There is another important factor that has to be considered – that is bioavailability. In a nutshell, its not just how much is in the food but rather how well you can absorb it. Clearly, if the gut cannot absorb the antioxidants, they will never get into the cells! The ease with which we can absorb any compound is called the bioavailability and this needs to be measured for each food and beverage individually to get an accurate picture of how good a source of antioxidants it is.

Antioxidants in beer

Cereal grains are a good source of antioxidants and not surprisingly beer, which is made from malted barley, also contains antioxidants. Therefore we decided to measure the bioavailability of one of these antioxidants, ferulic acid which comes from the barley cell walls.

This study was conducted in collaboration with Professor Catherine Rice-Evans and her team at Guys hospital and has just been published (Bourne et al 2000). The strategy of this study was to give 6 male volunteers a large dose of low alcohol beer, then follow the appearance of ferulic acid in the urine. The idea is that if ferulic acid appears in the urine this indicates that it must have been absorbed into the blood stream and therefore have been absorbed by the gut. Additionally, the speed at which it appears in the urine gives an indication of how long the ferulic acid stayed in the bloodstream and by implication whether it would remain in the body long enough to knock out oxygen radicals.

The results were very interesting. All of the ferulic acid present in the beer was absorbed by the volunteers. This is very different to the situation seen for a fruit such as the tomato. If volunteers eat fresh tomatoes they will maybe absorb only up to 25% of the ferulic acid in them, the rest remaining in the gut.

This difference in absorption of ferulic acid from tomatoes and beer can be easily seen in the figure. The reason for this is quite likely because the ferulic acid in the tomato is tied up in the cell walls and is physically prevented from passing through the gut wall. In contrast, the ferulic acid in beer is unbound and free in solution and is presumably easy to absorb. Another observation was that the ferulic acid stayed in the blood for longer than other antioxidants such as vitamin C. Ferulic acid would therefore be expected to be in the body for long enough to help with keeping free radicals at bay.

A note of caution.

Research is now telling us the amounts of antioxidants in our food and drink, and also how well we absorb them. However, two important questions remain in this story. First, once absorbed, do antioxidants get to the right tissue? Second, do antioxidants actually do any good when they get there? These are still active areas of investigation and so the case for the health benefits of antioxidants while receiving a lot of attention, is not yet entirely proven!

The take home message for beer, and indeed any food or beverage, is that antioxidant content must be assessed by both the total amount of antioxidant present AND how easily it is absorbed. The results so far indicate that beer should be a good source of antioxidants in the diet.

Conclusions

The health benefits associated with moderate alcohol consumption are now fairly widely accepted and the consumer is generally getting more interested in foods and beverages which can promote health – the so-called functional foods.

Red wine, cider and beer all contain antioxidants and it is reasonable to consider moderate consumption of these beverages as making a positive contribution to a healthy diet.

References

L. Bourne et al (2000) Bioavailability of ferulic acid from beer. Free Radical Research, 32:273-280

G. Paganga et al (1999) The polyphenolic content of fruit and vegetables and their antioxidant activities. What does a serving constitute? Free Radical Research 30:153-162

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Brewing Research International, Lyttel Hall, Nutfield, Surrey, RH1 4HY, UK
c.walker@brewingresearch.co.uk