Overlooking some one’s Scientific American on the plane home last night I saw the heading “A Milk-Diabetes Connection” which brought back memories of evangelical vegans arguing that milk was bad for you and lead to the development of diabetes. Juvenile diabetes, AKA Insulin Dependent Diabetes Mellitus (IDDM) or Type I Diabetes Mellitus, develops when the body is unable to produce insulin, the hormone which controls blood sugar levels. Mature onset or Type II Diabetes Mellitus is caused when insulin receptors are less sensitive to insulin and the insulin producing cells in the pancreas cannot keep up with demand.
Juvenile diabetes is thought to be an autoimmune disease as the body’s own autoimmune system destroys the cells with produce insulin (ref). These are the beta cells in the Islets of Langerhans of the pancreas and, somehow, the body considers them or their surface proteins to be invaders, attacking them which leads to their destruction. As with most autoimmune diseases the triggers are not always obvious and in the case of IDDM it may be a virus or other type of infection. In addition, IDDM also has a genetic component.
Some researchers, and evangelical vegans, suggest that a cow’s milk protein is the immune trigger (ref). As the newborn intestine is not fully formed, proteins can cross into the blood stream and trigger an immune response by acting as an antigen (ref) causing an antibody to be produced*, which then attacks the beta cells as they may have a surface protein with an analogous structure to cow’s milk protein.
The question is which protein? Animal studies suggested that bovine serum albumin (BSA) was the trigger and this was confirmed when a study in 1992 (ref) showed that:
Patients with insulin-dependent diabetes mellitus have immunity to cow’s milk albumin, with antibodies to an albumin peptide that are capable of reacting with a beta-cell–specific surface protein. Such antibodies could participate in the development of islet dysfunction.
A recent study from January, probably the one reported in SciAm, suggested that beta lactoglobulin was to blame. This protein is absent from human milk but it is in cow’s milk. This study showed a strong link between diabetes and cow’s milk formula consumption as the researchers found that five children with IDDM who were also fed cow’s milk had antibodies to beta lactoglobulin. A direct link to these antibodies to surface proteins on the beta cells still needs to be shown.
If cow’s milk consumption is a trigger for diabetes, it is only for young children under a year old. Once the digestive system matures, there is little risk of proteins crossing into the blood stream and causing an immune response. Thus, the age at which cow’s milk is introduced into the diet is important and probably should not be introduced until the child is over a year old.
Other References Used:
BNET: Cow’s Milk Diabetes Connection Bolstered (Not sure if Bovine Insulin and BSA are the same)
TRIGR: About page TRIGR means Trail to Reduce IDDM [Insulin Dependent Diabetes Mellitus] in the Genetically at Risk
*If you need to understand this further an introduction to cellular immunology is here.
If any one knows of a good basic introduction to immune response, please link to it in the comments as I could not find one.