Dr John Briffa: No jacket required

The potato is a versatile vegetable and can surface in our diet in a variety of guises. Some of these, such as crisps and chips, are not held in high nutritional regard. However, less fat-packed forms of potato are generally seen as healthy fare, with the jacket potato often regarded as the pick of the crop. Low in fat and high in fibre, these starch-filled orbs are seen as wholesome and slimming food, ideal for filling our stomachs, but not our trousers or skirts.

At least some of the baked potato's healthy allure seems to come from the vitamin C and fibre it reputedly has to offer. Actually, potatoes tend not to compare well with other vegetables in the nutritional stakes. For instance, baked potatoes contain significantly less fibre than broccoli and offer only a fraction of the vitamin C. Another of the potato's supposed selling points is the ability of the starch contained within it to provide a source of fuel for the body. Here again, however, it appears as though the potato does not stack up at all well.

The speed and extent to which a standard quantity of food increases blood sugar levels is referred to as its glycaemic index (GI). Glucose, a sugar that is absorbed rapidly from the gut, is assigned an arbitrary GI of 100. In comparison, baked potatoes have a hefty GI of 85. While conventional wisdom dictates that baked potatoes release sugar slowly and steadily from the starch they contain, the reality is that their effect on blood sugar levels is disturbingly similar to that of pure sugar itself.

In response to the sugar surge that a baked potato may induce, the body will tend to make copious quantities of the hormone insulin. Insulin's prime job is to keep blood sugar levels from rising too high, but too much of it can be a bad thing. In excess, insulin can drive blood sugar to subnormal levels, which can lead to a variety of undesirable symptoms. In my experience, a baked potato eaten for lunch will tend to precipitate a distinct slump in energy in the afternoon, accompanied by an urge to raid the biscuit tin. In the longer term, a glut of insulin can have dire consequences for our body. Insulin stimulates the conversion of sugar into fat, which then dumps itself around the midriff. Plus, high levels of insulin can cause the body to become relatively immune to the effects of this hormone, paving the way for diabetes in later life.

While baked potatoes have the capacity to destabilise the body's chemistry, this is not so true for other forms of potato. New potatoes have a more measured effect on blood-sugar balance, reflected in a GI of 57. Also, it's worth bearing in mind that the sugar-releasing effects of potatoes can be tempered by eating them in moderation and combining them with stabilising foods such as meat, fish and non-starchy vegetables. In this way, a piece of salmon accompanied with some broccoli and a few new potatoes represents a well-balanced and healthy meal for most. As for big baked potatoes, however, I don't dig them at all.

Nutrition news

The incidence of breast cancer in the UK has risen steadily over the past three decades and it is now the commonest form of cancer in women. One risk factor for breast cancer appears to be alcohol, with studies suggesting that even moderate drinking may increase a woman's susceptibility to the disease. However, research has found that additional quantities of one nutrient - folate - may help to protect against the increase in breast-cancer risk associated with alcohol. A study published recently in the Journal of the National Cancer Institute found that in women drinking at least one unit of alcohol a day, those with the highest levels of folate had an 89 per cent reduced risk of breast cancer compared to those with the lowest levels. Risk reduction in women drinking less than one unit was 28 per cent. Folate is important for the functioning of DNA, a glitch which may cause the division of cancer cells. Sources of folate include oranges and green vegetables. Women drinkers looking for additional protection from breast cancer might do well to supplement with 400mcg of folic acid per day.

Dear John

I have damaged a disc in my back playing rugby. Surgery has been mooted, but I'm cautious about this. Is there something I can do to help heal the damage?
Mike Hurst

The spongy pads that lie between the bones of the spine are called intervertebral discs. Each disc is composed of a hardy outer layer with a soft jelly-like centre. Damage to discs can cause pain and a degree of immobility in the back. Each disc in the spine contains a substance called collagen. Collagen is largely responsible for the strength and resilience of the intervertebral discs. Vitamin C has a very important part to play in the formation of collagen, and taking this nutrient in supplement form does seem to help prevent further disc damage. Back in the 60s, a Texan orthopaedic surgeon reported that giving vitamin C (1.5-2.5g per day) to his patients with disc problems would often alleviate their pain and spare them surgery. Another useful agent in the treatment of disc problems is glucosamine sulphate. Glucosamine is the building block in the tissue of which intervertebral discs are comprised. Taking 500mg of glucosamine sulphate, two or three times a day, should help to stimulate healing and repair the damaged disc in the long term.

Thanks to guardian.co.uk who have provided this article. View the original here.