Why Christmas pudding is good for you

These can help head off high blood pressure, provide energy-boosting iron and are rich in protective antioxidants.

It is estimated that one in three Britons suffers from hypertension which is a major risk factor for strokes and heart disease. Earlier this year a study presented at the American College of Cardiology reported that regular snacking on raisins reduced blood pressure readings by up to 10 per cent in just 12 weeks.

Dr Harold Bays, the American scientist who headed the study, said: “Raisins are packed with potassium which is known to lower blood pressure. They are also a good source of antioxidant dietary fibre that may cause blood vessels to be less rigid which in turn may reduce blood pressure.”

One ounce of raisins provides around 50mg of iron or about the same as in an ounce of steak, making them a great source of this vital mineral for vegetarians.

Like raisins, sultanas are dried grapes and share many of their health benefits including potassium and iron. Sultanas are a source of calcium, magnesium and manganese which strengthen bones and help head off osteoporosis.

About three million people  have this bone condition. It is responsible for more than 250,000 fractures annually.

Sultanas also contain traces of selenium which appears to protect against cancer. According to the American Cancer Society selenium “shows promise as a nutrient that may help prevent the development and progression of cancer”.

With four times the immune-boosting vitamin C of oranges, several studies suggest currants can help combat winter sniffles by inhibiting the flu virus, reducing inflammation in the airways and boosting levels of friendly gut bacteria that strengthen the immune system.

They are also rich in anthocyanins, plant chemicals that could reduce the risk of cancer. Laboratory studies have shown anthocyanins are able to switch off genes that make tumour cells grow and trials are under way to see if they will help patients with prostate and colon cancer.

Almonds and other nuts help bring down cholesterol levels. A study at the University of Toronto found volunteers who ate a handful of almonds a day reduced their levels of LDL cholesterol (the “bad” form which increases the risk of heart disease) by four per cent.

Don’t be deterred by the fact nuts are quite high in fat, around 22 per cent.

Dr David Jenkins who led the trial said: “The combination of monounsaturates with some polyunsaturates in nuts is an ideal combination of fats, all of which may have a beneficial effect on blood cholesterol.”

Several studies have shown nuts can be an important part of any weight-loss diet.

Nuts are also rich in vitamin E which is essential for healthy skin and hair and is much more readily absorbed by the body in this natural form than in supplements.

These are an excellent source of vitamin D, a nutrient under increasing focus as a key factor in immunity and general health.

Vitamin D is essential for healthy bones and a deficiency of it is known to cause conditions such as rickets. There is a mounting body of evidence to suggest it also reduces the risk of heart disease, cancer, asthma in children, dementia and a host of serious health problems.

Insufficient levels of vitamin D have been linked to autoimmune disorders. The Multiple Sclerosis Society says studies suggest vitamin D deficiency plays a role in the risk of developing MS although it is not yet clear what this might be.

Vitamin D deficiency is common , particularly in winter when our bodies cannot get enough from the sun. The Government recommends children under five, pregnant or breast-feeding women, the over-65s and other at-risk groups take a daily supplement.

This contains a number of aromatic antioxidants such as allspice, cinnamon, cloves, ginger and coriander which can deliver a health boost.

A study published in the Journal of Food Science reported that allspice, cinnamon and cloves contain compounds which attack the food-poisoning bugs salmonella, E-coli and listeria.

Ginger can relieve nausea and vomiting and is often recommended to combat morning sickness. According to the US National Institute of Health it can help reduce problems after surgery.

One study found ginger reduced nausea and vomiting by as much as 38 per cent after operations. Cinnamon and coriander lower blood sugar levels and improve insulin production which in theory should help reduce the risk of diabetes.

The plant chemicals in citrus peel go by the catchy name polymethoxylated flavones or PMFs. Research backed by the US Department of Agriculture suggests they could play an important part in controlling cholesterol levels.

Dr Elzbieta Kurowska, who headed the study, says: “We believe PMFs have the potential to rival and even beat the cholesterol-lowering effect of some prescription drugs without the risk of side effects.”

Studies have also suggested citrus peel can protect against cancer, heart disease and inflammation.