For centuries, salt has been revered as a flavour enhancer and food preservative across the globe. Our appetite for salt has not diminished either: many of us add salt during cooking or at the table, and salt has a ubiquitous presence in pretty much every processed food. Some salt appears to be important for maintaining balance in the body's biochemistry. However, as with everything, it is possible to get too much of a good thing. Research suggests that too much salt can push blood pressure up, increasing the risk of circulatory diseases such as heart disease and stroke. The evidence suggests that health consequences of bagfuls of salt in the diet can be quite unsavoury.
Many studies have suggested that high levels of salt consumption can boost blood pressure. Not surprisingly, the salt industry has also been vociferous in defending its commodity. However, despite the protestations of the salt-sellers, a sea of scientific research over the last 10 years supports the notion that salt can contribute to problems with high blood pressure.
Blood pressure is measured in millimetres of mercury (mmHg), and is expressed as two values, one over the other, eg 120/70. The upper value refers to the systolic pressure - the maximum pressure that occurs during contraction of the heart. The lower value, or diastolic pressure, is the resting pressure in the system between heartbeats. Heightened blood pressure has long been seen as a major risk factor for heart disease and stroke. A recent study in the Lancet found that, in individuals aged 40 to 69, an increase in systolic blood pressure of 20mmHg was associated with a doubling in risk of death due to these conditions.
Studies suggest that reductions in salt intake might have important implications for public health. Recently, researchers from the Blood Pressure Unit at St George's Hospital, London, assessed data from 29 trials examining the effect of salt reduction on blood pressure. The data suggest that if we in the UK halved our salt consumption, we would see meaningful reductions in blood pressure in the population. Relieving pressure in the circulation by reducing salt in the diet is expected to translate into a 9 and 14 per cent reduction in deaths due to heart disease and stroke respectively in those suffering from high blood pressure. Interestingly, though, even those classified with normal blood pressure are likely to reduce their risk to some degree.
Most of the salt we consume comes from processed food. Savoury snacks, tinned vegetables, cheese and processed meats are obvious sources. But large amounts of salt can make their way into some unlikely places - cornflakes, weight for weight, are even saltier than seawater. Cutting back on our intake of pre-packaged foods, and the salt they contain, is one strategy almost certain to help preserve our health in the long term.
A high-fibre diet has long been believed to help reduce the risk of cancer of the colon - the second most common cause of cancer death in the UK. One way fibre is thought to protect the large bowel is by speeding the passage of waste matter through it. Toxic substances in faeces are believed to have the capacity to exert a cancer-inducing effect on the wall of the bowel. By reducing the risk of any hold-ups in the colon, fibre in the diet is believed to help reduce the chance of toxic chemicals having such an effect. However, recent evidence suggests that another benefit of a high-fibre diet is that it provides plenty of the nutrient folate. More than one study has found that high levels of this vitamin are associated with a reduced risk of colon cancer. Folate is believed to protect DNA in the body's cells from changes that are at the heart of the cancer-causing process. The evidence suggests that eating plenty of foods rich in both fibre and folate such as broccoli, asparagus, spinach, Brussels sprouts, and beans and pulses will help to keep the colon cancer-free.
I had a bad cold in December and since then have noticed that my sense of taste has all but disappeared. Is this likely to be permanent, or do you think I might be able to do something about it? I am 52.
Mary Glover by email
The sense of taste appears to be quite dependent on an adequate supply of zinc in the body. Zinc is also known to be important for the function and effectiveness of the immune system. My suspicion is that infections such as cold and flu can deplete zinc levels in the body, diminishing the sense of taste as they do this. Whatever the explanation, my experience is that supplementing with zinc often restores a sense of taste after a viral infection.
I recommend that you keep your diet relatively rich in zinc-rich foods including seeds, seafood and fish. In addition, I suggest you take 100mg each day of either zinc ascorbate or zinc citrate (each will provide about 30mg of actual zinc per day). Because zinc can induce copper deficiency in the body, it is a good idea to take about 2mg of copper each day along with this. Several weeks or possibly months of this treatment is likely to bring back your sense of taste in time.