Margarine manufacturers say butter is bad for you. Butter producers say margarine is unnatural. The sugar industry funds research into the dangers of artificial sweeteners. And the drug companies say sugar is deadly. Who do you believe?

A doctor friend last summer received an invitation to attend an important-sounding conference on 'New Directions in Cardiology'. Being a diligent sort of chap and one who was genuinely interested in the welfare of his patients, he decided to go along, especially as the literature accompanying his invitation seemed to say that everything he had once thought was a relationship between heart disease and the high consumption of dairy fats was mistaken and old hat. He thought he might learn something new.

He told me that he did.

Meeting an old friend colleague there, he was asked, "Doctor Roberts? Do you remember me? We met last at the Flora margarine conference on heart disease last year. They were blaming it all on milk and butter then. It looks like this one's sponsored by the Butter Information Council and they say it's everything except dairy fats. A bit of a joke really, isn't it? So, tell me, who's right."

Unfortunately, when I heard this and at the risk of sounding over-modest - how the hell do I know? I'm only a journalist! But, as a researcher in quest of truth that makes me feel terribly alone. If every source has an axe to grind then whom can I turn to for impartial advice? The government perhaps? Well it doesn't have a very good track record either.

Take a typical example: salt. It has been established that hypertension - high blood pressure - is a contributory factor to heart disease. Around ten per cent of the whole population suffers from it, and 20 per cent of people over the age of 40. Half of those who have high blood pressure don't know it because they've never taken their complaint to a doctor. No one disputes any of these assertions. Nor is there much controversy about the fact that people with high blood pressure can ameliorate their symptoms by reducing their salt intake. What is debated, however, is whether a high salt intake causes high blood pressure.

It isn't surprising that this is a matter of dispute. A recommended daily intake of five grams of salt per day is about right. But at present simple arithmetic shows that, even if we were to reduce the salt we add ourselves to zero, we would still, on average, be taking in nearly double the recommended amount.

From where does most of our salt intake come? Manufactured foods, that's where: Soups, gravies, burgers, meat products, bedtime drinks. Bedtime drinks? That's right. And then there are those innocent looking breakfast cereals. An average helping of All Bran in the morning would give you just about your entire five gram allowance. Any you consume during the rest of the day is excess. It's in bread, beans and biscuits. Another doctor friend of mine wondered why so many of his F-Plan diet devotees were showing an increase in their blood pressure… until he discovered the diet's salt content. Admittedly food manufacturers aren't deliberately trying to give us heart disease. They use salt simply because we're just so darn used to it; it's strong - and it's cheap.

So, until the government forces the food industry to limit the amount of salt they use on or in their foods to entice to buy their products, (Can you imagine a reduction of salt on your potato chips?), them I'm afraid we are in for it!