Guide to cranberry

Best known for being served with roast turkey at Christmas, cranberries have also been used medicinally for centuries in traditional herbal medicine.

Sour, ruby-red cranberries are a Native American plant closely related to the blueberry. The name is a shortened form of ‘craneberry’, because the flowers of the shrub were thought to resemble the heads of the cranes that lived in the bogs where it grew.

Now popular as a supplement scientists have found cranberries, often referred to as a ‘superfood’, are packed with high antioxidant properties that may help a variety of health problems.

Dr Sarah Brewer says: ‘Naturally-sourced extract of fresh cranberries is packed with a unique type of antioxidant-rich polyphenols, called PACs, that may support a healthy bladder and have beneficial effects on several risk factors associated with stroke, heart disease and diabetes.’

What does cranberry do?

Cranberries are packed with nutrients, including vitamin A (beta carotene), vitamin C, lutein, manganese, potassium and folate. The flesh and juice of the cranberries contain antioxidants called polyphenols which may protect other cells in the body from damage by free radicals, including those in the heart and the arteries.

Cranberries also contain a high level of proanthocyanidins (PACs), a class of polyphenols, which help reduce E. coli bacteria from sticking to the lining of the bladder and urinary tract, allowing the bacteria to be flushed out.

Urinary tract infections

Many women who are prone to recurrent urinary tract infections (UTIs) such as cystitis – an inflammation of the bladder which causes pain when passing urine and increased urinary frequency – use cranberries as a preventative treatment.

There have been several clinical trials that have investigated the effectiveness of cranberry extracts and juices in preventing UTIs. Many of them have shown that a cranberry supplement can significantly reduce the number of UTIs that women suffer – but the evidence is mixed. Many people in trials stopped taking cranberry juice, suggesting they didn’t find it acceptable. A supplement is a great alternative as it supplies the PACs in an easy-to-take way.

One recent 24-week study in 2016, by Boston University, looked at 373 women who had suffered with two UTIs the past year. Half of the participants drank 227ml of cranberry juice a day, whilst the others drank a placebo. Researchers discovered drinking cranberry juice decreased UTIs by 40 per cent, with just 39 diagnoses compared with 67 in the placebo group.

Heart health

Heart and circulatory disease is a leading cause of death and disability in the UK, but following a healthy lifestyle by reducing some of the risk factors – such as being overweight, having high blood pressure, raised cholesterol and not taking exercise – can prevent it developing.

Some evidence suggests polyphenols in cranberries may reduce the risk of the disease by preventing blood platelet build-up and reducing blood pressure via anti-inflammatory mechanisms. A study by the US Department of Agriculture, found people who drank cranberry juice each day improved blood pressure, blood sugar levels and blood lipids, compared to a placebo group.

Getting cranberries from your diet

You can drink cranberries in either juice or as a tea. Cranberries are available fresh from some supermarkets or dried in many health food stores, and can be added to puddings, jams, porridge or fruit salads. Alternatively, take cranberry in supplement form.


Cranberries appear to be safe for most people, although large amounts can cause stomach upsets and may increase the risk of kidney stones. Avoid cranberries if you’re on blood-thinning drugs such as warfarin. Cranberry is safe to take during pregnancy and while breastfeeding.

If you suspect you may have a UTI, always seek medical advice. This is especially important in children, during pregnancy, or if you develop a fever. Remember, a cranberry supplement is not a substitute for antibiotics though.

Correct dosage

There is currently no UK or EU recommended daily allowance or upper safe limit. A typical dose of standardised cranberry extract is two 277mg supplements a day. A 277mg extract supplement is equivalent to 10,000mg of whole fresh cranberries.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

Naturally-sourced extract of fresh cranberries is packed with a unique type of antioxidant-rich polyphenols, called PACs, that may support a healthy bladder and have beneficial effects on several risk factors associated with stroke, heart disease and diabetes.

Dr Sarah Brewer


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