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Did you know that prunes regulate blood sugar and strengthen bones?


Did you know that prunes regulate blood sugar and strengthen bones?

Credit: Monika Grabkowska

While Prunus domestica is the most common plum used, a prune is a dried plum of any of the 1000 or so varieties available worldwide. Prunes can be used in cooking for both sweet and savoury dishes and have even been made into a highly alcoholic drink similar to cider, called jerkum.

Active ingredients

Prunes are high in phenolic compounds such as chlorogenic and neochlorogenic acids, sorbitol and both soluble and insoluble dietary fibre (7 per cent). This fibre contains a significant amount of the prebiotic inulin and pectin. Prunes are high in the potent antioxidant and anti-inflammatory compounds (anthocyanidins), giving them the highest antioxidant capacity of any dried fruit, and a range of vitamins (particularly vitamins B6 and K) and minerals (potassium, manganese, boron and magnesium).

Therapeutic uses

Gastrointestinal

Prunes have been used for many years as a mild laxative and digestive normaliser due to the fibre content as well as natural sorbitol (a sugar alcohol that by not being absorbed can act as an osmotic agent, resulting in a laxative effect). Prunes have been shown to be more effective than psyllium husks to relieve constipation.

Preventing constipation (it has been estimated that 14 per cent of the population suffer from constipation globally) is vitally important for health, as suffering from these symptoms can significantly impact on health-related quality of life measures. Preventing constipation with safe functional foods such as prunes helps to prevent long-term bowel problems such as diverticulitis and bowel cancer.

Chlorogenic acid from prunes is metabolised by specific microbiota, generating a food source that stimulates the growth of bifidobacteria, a critically important component of a healthy bowel microbiome (although no specific trials have investigated this).

Prunes are considered a safe, effective functional food and play a significant role in managing gastrointestinal health, as part of a general dietary modification plan.

Cardiovascular

The high phenolic content of prunes reduces the oxidative damage to lipid (fat) molecules. These phenolics inhibit the oxidation of LDL cholesterol, helping prevent damage due to abnormal cholesterol levels. In cholesterol metabolism it’s not necessarily the LDL level specifically that can potentially cause problems; it’s the oxidation of LDLs and the carrying of fat-soluble chemicals by them that are more the issue.

Research has shown that prunes inhibit LDL oxidation, thus potentially acting as a preventive agent against chronic illness such as heart disease and cancer. The high potassium level is also useful to maintain cardiovascular health.

The soluble fibre level helps to lower cholesterol by absorbing excess bile in the intestine and excreting it. This encourages the liver to produce more bile from cholesterol, thus reducing the amount in circulation.

Endocrine

Prunes provide a sweet hit with low calories, and the soluble fibre in prunes assists in the regulation of blood sugar levels as it slows the rate at which food leaves the stomach and therefore slows glucose absorption into the bloodstream. With a glycaemic index of 29, unsweetened prunes have a lower glycaemic index than many other fruits despite their relatively higher sugar content. This also assists in the prevention of diabetes by regulating blood sugar management.

Bone health

Interestingly, prunes have been shown through research to assist in the prevention of osteoporosis by strengthening bone. A unique property of prunes, unknown in most fruits, is the ability to restore bone and prevent further bone loss in osteoporosis. Prunes downregulate osteoclast (catabolic or breaking-down bone) while upregulating osteoblast (anabolic or building-up bone) activity, thus not only protecting against but actively reversing bone loss.

Prunes have been shown through research to assist in the prevention of osteoporosis by strengthening bone.

Prunes improve bone mineral density, trabecular bone microarchitecture and biomechanical properties (strength and stiffness), largely due to their polyphenol content. While dried apricots and grapes have shown lesser ability to protect bone, prunes are the only fruit to have an anabolic (bone-building) effect, particularly in the spinal vertebrae.

The high content of boron in prunes also plays a role in the prevention of osteoporosis. A serving of 100g of prunes gives 2–3mg of boron — the daily requirement for bone health.

Antioxidant

The antioxidant components of prunes have the property of upregulating glutathione activity, thus improving antioxidant status in the body. Glutathione has also been shown to be involved in the suppression of bone resorption (even when associated with an oestrogen deficiency).

Conclusion

Overall, prunes are a delicious and healthy way to maintain health, a functional food that helps to prevent many of the chronic illness plaguing our Western society.

One word of caution: unfortunately, prunes can contain acrylamide (a potential neurotoxin) formed during the processing if dried at high temperatures, so be careful of dosage. The potential dosage to have this effect is calculated to be 500 times an average daily dosage so this is not usually an issue.



 

Dr Karen Bridgman

Dr Karen Bridgman is a holistic practitioner at Lotus Health in Sydney.