A biological basis for why the risk of inflammation associated with autoimmunity and allergy has increased due to changes in the Western diet, has been found by scientists at the American Society for Biochemistry and Molecular Biology. The major changes in Western diet have altered the consumption of omega-6 fatty acids (w6) compared with omega-3 fatty acids (w3).
Anthropological evidence suggests that human ancestors maintained a 2:1 w6/w3 ratio for much of history, but in Western countries these days the ratio has spiked to as high as 10:1.
Given that these omega fatty acids can be converted into inflammatory molecules, it is believed that his dietary change also disrupts the proper balance of pro- and anti- inflammatory agents, and thus leads to increased systemic inflammation and a higher incidence of problems like asthma, allergies, diabetes and arthritis.
In order to determine whether these fatty acids might have other effects, Floyd Chilton and colleagues developed a dietary intervention strategy in which 27 healthy humans were fed a controlled diet mimicking the w6/w3 ratios of early humans over 5 weeks.
The researchers then looked at the gene levels of immune signals and cytokines, protein immune messengers that impact autoimmunity and allergy in blood cells.
They found that many key signalling genes that promote inflammation were markedly reduced compared to a normal diet, including a signalling gene for a protein called PI3K, a critical early step in autoimmune and allergic inflammation responses.
The researchers claim that their study is the first that has shown in humans that large changes in gene expression are likely an important mechanism whereby these omega fatty acids exert their potent clinical effects.