Placebos play an important part in scientific trials.

After two weeks, the patients were split into two groups, one of which began an elimination diet. For the first week, this diet consisted of twelve rarely eaten foods. All milk products, eggs, cereals, beverages and additives were excluded, along with most meats and all commonly eaten fruits and vegetables.

After the first week, these excluded foods were reintroduced, one at a time. Any foods that caused a flare-up of symptoms were not eaten again. The assessment of the patients continued for six weeks – long enough for them to have tested most foods and established a workable diet that excluded all ‘incriminated’ foods.

While the first group of patients was undergoing the elimination diet, the other group kept on taking their dummy tablets. After six weeks they were told that a different form of treatment would be tried – and they were then put on to the elimination diet. The objective here was to use the second group to assess the placebo effect – the improvement that is produced by any new form of treatment. Their response during the first six weeks on the dummy tablets was a measure of the placebo response that might be expected in the other group during the elimination diet.

The joint symptoms of all the patients were assessed using various standard measurements of pain and stiffness, plus routine blood tests that help evaluate the severity of rheumatoid arthritis. Dr Ramsey, who was unaware of which patients belonged to which group, and was therefore unbiased, made the assessments. The patients who received the dummy tablets first did show some improvement – so there was a placebo effect – but the group that undertook the elimination diet did far better. When the placebo group later went on to the diet, they too showed a much more striking improvement.

Notice that these measurements are a rather crude assessment of improvement in the group as a whole: when considered individually, some showed little change while others seemed to respond dramatically to the treatment. (The reasons for assessing patients as a ‘job lot’, rather than individually, will become clear when we look at the next trial.) At the end of the diet, three-quarters of the patients claimed to feel ‘better’ or ‘much better’ than at the outset.

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