Our regular columnist, Mr. Metabolism, addresses the current issue regarding cow's milk and its possible link to diabetes.

It seems that new scientific evidence can teach me whom to blame for my diabetes: my mother. Did she doom me to a life of insulin injections for love of cow's milk? I needed to know what milk she had given me. I called her.

"Mom, I want to talk about breast feeding."

"What?"

"How old was I when I started on cow's milk?"

"Well, your sisters were breast fed for a year and three months, but by the time you came along I was so busy that you went right on to milk."

"Formula or cow's milk?"

"You were on formula for a few weeks but you gained weight too fast so we switched you to skim milk."

Neither of my sisters have developed diabetes. I have. Thus came out the truth: It was all my mother's fault!

Scientific studies very often cause people, especially those who are sick, to leap to incorrect conclusions. A major goal of medical research on diabetes is to answer the question, "What is the cause of diabetes?" This question has not been answered, and with today's "Formula or cow's milk?"

"You were on formula for a few weeks but you gained weight too fast so we switched you to skim milk."

Neither of my sisters have developed diabetes. I have. Thus came out the truth: It was all my mother's fault!

Scientific studies very often cause people, especially those who are sick, to leap to incorrect conclusions. A major goal of medical research on diabetes is to answer the question, "What is the cause of diabetes?" This question has not been answered, and with today's science, cannot be answered. But the suffering of millions and the pathos of the children with diabetes call out for an explanation.

And explain we do: humans have a need to find explanations and create causes where none can be known. What does it mean to say that a disease has a cause? Causation is a notoriously slippery concept.

In medicine we usually restrict the concept of sole cause in the following way. For A to cause disease B, A must be necessary and sufficient. Necessary means that whomever has disease B has experienced cause A. Sufficient means that given cause A and no other cause, you will develop disease B.

There are few clear examples of sole cause in medicine-an extremely virulent infectious disease is the most clear. If you are exposed to the right virus, you will get black plague. Everyone with black plague was exposed to the pathogen. Thus we say with certainty that the plague is caused by this virus.

A recent study was published that showed a correlation between the age a baby first drinks cow's milk and the likelihood that he/she later develops diabetes. Previous studies had hinted at this cause. Is it possible that cow's milk is the "cause" of diabetes?

No, not really. You might just as well say that cold winters are the cause of diabetes (diabetes is forty times more common in cold, northern countries than near the equator). Cow's milk is neither necessary nor sufficient to cause diabetes. Many children who are fed with breast milk for over a year develop diabetes. And many children fed with cow's milk early in life never develop diabetes.

So what is going on? Many studies have shown that the way the insulin-producing islets of Langerhans die in most diabetics is from autoimmune attack on the islets. What is observed is infiltration of the islets with cells from the immune system such as macrophages and T cells. Other lines of evidence support the concept that the immune system mistakenly identifies a protein that is normally found on islets as being "foreign," and therefore the islets ought to be destroyed.

Is this autoimmune attack the "cause" of diabetes? Well, it seems to be necessary, but it is certainly not sufficient. One might think that, once an autoimmune attack on the islets starts, it will always lead to diabetes. This turns out to be incorrect! Using tests that specifically detect autoimmune attack on islets, British scientists studying school boys showed that over 20% of them had ongoing autoimmunity. Since only about 1/2% will develop diabetes in their lives, most children with autoimmunity against their islets will never develop diabetes!

Thus, a somewhat different picture emerges. Perhaps islet autoimmunity is fairly common, but somehow the immune system keeps the problem in check and the islets can repair themselves as fast as the immune system destroys them. Many factors are involved in triggering islet autoimmunity. Perhaps the proteins in cow's milk play a role-even a major role-in triggering autoimmunity. Autoimmunity is complex and poorly understood, and autoimmunity is far from the whole story.

So don't blame your mother for your diabetes! I know I don't.

Mr. Metabolism (S. Robert King) has a masters degree from Harvard in Biochemistry and is a former biotechnology analyst with Montgomery Securities. Besides having type I diabetes, Mr. Metabolism is currently V.P., Technology for Metabolex, a biotechnology research firm in Hayward, CA.