Not traditionally the most fashionable fruit in the bowl, the humble prune is enjoying an image makeover. In a climate of increasing concern about health and nutrition, dried plums are packed with antioxidants and packing a punch, as Kate Barker discovered.

Relaxing in a deckchair, sand beneath my feet, with the gentle sound of waves crashing on a distant shore, I could almost believe I was on a beach in sun-drenched California. But alas, it was just an illusion. While the sand and the deckchairs were real, they were inside a small marquee in the grounds of a country hotel in Leicestershire, UK, and the ocean waves were originating from a sound system at the back of the tent. For this was a promotional "beach party" event hosted by the California Prune Board, a marketing body formed to look after the interests of prune growers in California, and I was about to find out that there is more to the humble prune than meets the eye.

Prunes, or dried plums as they are known in the US, are believed to have originated in Western Asia near the Caspian Sea, and were introduced to North America in 1856 by a French nurseryman in search of Californian gold. The prune plums that now grow widely in California are an offshoot of the d'Agen variety, which is native to Southwest France. Although prunes are still produced in other parts of the world, the US is the world's main prune producer, and the vast majority of the country's prune production is centred in California.

With more than 80,000 high production acres, California produces more than 60% of the world's prunes, and around 99% of the prunes purchased in the US. In the last crop year California produced over 207,000 metric tons of the dried fruit. The state's fertile soils and intense sunshine provide ideal growing conditions for plums, ensuring an abundant crop. After harvesting, the plums undergo a quality control process and are then dehydrated for 18 hours and stored in wooden containers. Once orders for the prunes arrive, the fruit is rehydrated and sterilised, and is then ready for packing.

One of the top importers of California prunes is the UK, which buys around 6,500 metric tons per year. The California Prune Board, supported by the US Department of Agriculture, carries out a marketing programme in the UK that focuses primarily on the fruit's health benefits. Amid increased competition from other prune exporters, and a reduction in home baking, the board is keen to emphasise the health benefits of prunes, while also highlighting the strict quality control methods used by California prune growers and packers.

Fighting free radicals

In this current climate of interest in all things healthy, it was fascinating to learn that prunes have extremely high levels of antioxidants, which are believed to protect against some cancers and slow the ageing process. Antioxidants fight cell-damaging free radicals, which are harmful chemicals produced when the body burns oxygen, but which also get into our system through smoking, environmental pollution, radiation, excess sunlight, and by contact with chemical irritants.

The US Agricultural Research Service's Human Nutrition Research Centre on Ageing, based at Tufts University in Boston, has established a system of measuring the total antioxidant powers of individual foods. Each food is ranked by its oxygen radical absorbance capacity (ORAC), in other words the food's ability to fight free radicals. Prunes were found to have an ORAC value of 5,770 per 100g, the highest ORAC value of all commonly eaten fruit and vegetables. The second-highest scoring fruit was the raisin, which, with an ORAC score of 2,830 per 100g, does not even come close to the high-scoring prune (Figure 1). According to the researchers, the optimum daily intake of ORAC units is 3,000, while for maximum protection 5,000 ORAC units should be consumed each day.

Figure 1. ORAC ratings of commonly eaten fruit and vegetables per 100g

Prunes
5,770
Spinach
1,260
Raisins
2,830
Raspberries
1,220
Blueberries
2,400
Brussels Sprouts
980
Blackberries
2,036
Plums
949
Garlic
1,939
Broccoli
890
Kale
1,770
Beetroot
840
Cranberries
1,750
Avocado
782
Strawberries
1,540
Oranges
750

Source: The Oracle Diet by Michael Van Straten

One of the guest speakers at the California Prune Board's beach party was Michael Van Straten, a broadcaster, writer and naturopath who believes that nutrition is at the root of good health. Van Straten, author of The ORACle Diet, a book that explains the importance of ORAC foods and also provides recipes for meals with high ORAC values, described prunes as "one of the great nutritional foods of our generation", which we need now more than ever before. Besides their high antioxidant value, prunes are also rich in iron, potassium, fibre and vitamins A and C. They are also fat free and contain only ten to 12 calories per prune, Van Straten said. Unsurprisingly, many of Van Straten's recipes in The ORACle Diet contain prunes, which he describes as a versatile fruit. Besides adding prunes to porridge and other cereals, Van Straten suggests meals such as braised duck with prunes, trout with prune relish, prune and chocolate terrine, and prune soufflé.

Preventing bone loss

The California Prune Board has part-funded a number of studies into the nutritional and health benefits of prunes, including research into the fruit's effect on osteoporosis. The study, led by Dr Bahram Arjmandi at Oklahoma State University, found that prunes may also contribute to the prevention of bone loss in postmenopausal women. In the results of the three-month clinical trial, women who ate 12 prunes per day showed increases in biomarkers of bone metabolism, reflecting a higher rate of bone formation. Arjmandi said that if this positive effect were to continue for a longer time, prunes could produce clinically significant increases in bone mass, thereby fighting osteoporosis, or bone loss, in postmenopausal women. According to the UK's National Osteoporosis Society, one in three women in the UK will suffer from osteoporosis over the age of 50.

Such studies, together with the already proven health benefits of prunes, may go a long way towards persuading consumers to eat prunes as part of their everyday diet. In the UK, prunes are not fashionable and are somewhat maligned, with many people associating them with having a laxative effect. However, as consumers' concerns about healthy eating rise, and as the popularity of functional and healthy foods increases, consumer awareness of antioxidants has risen, with some food manufacturers even focusing advertising campaigns around a product's antioxidant properties. People are increasingly self-medicating through diet and supplements, and informing consumers of the antioxidant content and other health benefits of prunes can only serve to increase the fruit's popularity.