May 20 2004
Eating large amounts of antioxidant vitamins (vitamins A, C and E) is unlikely to prevent heart disease and other diseases such as cancer according to a new study by the Universities of Bristol and London published in this week’s edition of The Lancet.
The study found that individuals who have diets rich in these vitamins are people who are less likely to have ever lived in deprived social circumstances, less likely to have ever smoked, more likely to be physically active and less likely to be obese. It is these factors rather than the vitamins that protect individuals from disease.
Dr Debbie Lawlor and colleagues reviewed previous studies and undertook new research. This new research found that even one’s father’s job and household conditions in childhood, such as whether the house one lived in as a child had a bathroom or running hot water, were strong predictors of levels of antioxidant vitamins in the blood.
The study was conducted in 4,000 women from all over Britain who had blood tests when they were aged 60-70 years old. Smoking, physical activity, obesity and current social conditions were also strong predictors of vitamin levels in the blood.
"People should be encouraged to eat a healthy diet with plenty of fruit and vegetables but there is no evidence that taking vitamin supplements will prevent heart disease or cancer."
Dr Debbie Lawlor
In previous studies that had simply looked at dietary patterns or measured blood levels of vitamins and then compared disease occurrence between groups with different vitamins levels, the vitamins appeared to protect against a number of important diseases. However, this type of study is not able to take account of all of the factors – like early life housing conditions and lifestyles – that affect both vitamin levels and also diseases like heart disease and cancers.
In trials where individuals were ‘randomly allocated’ (a process similar to tossing a die) to vitamin supplements or not, supplements which produced similar blood levels to those that were shown to be protective in the earlier studies did not protect individuals from heart disease or other diseases. In this type of study the random allocation means that factors such as lifestyle can not confound the results.
Dr Lawlor said: “People should be encouraged to eat a healthy diet with plenty of fruit and vegetables and of course should take regular exercise and should not smoke, but there is no evidence that taking vitamin supplements will prevent heart disease or cancer.”