... ?Doi=67101

It's a bit hard to follow, so I've broken it up, replaced abbreviations and added my translation:

The Frequency of Multiple Sclerosis in Jewish and Arab Populations in Greater Jerusalem

A comparison of the incidence rate Incidence Rate and the Prevalence of multiple sclerosis (MS) in subgroups of the same ethnic origin, but born and living in different geographical areas, may delineate the relationship between environmental and genetic risk factors for MS. We found that the PREVALENCE RATE of MS in Israeli Jews is higher than Prevalence Rate previously described. Furthermore, the PREVALENCE RATE was significantly lower among immigrant Jews from Asia/Africa than among native-born Jews of Asian/African origin.

Translation: Immigrant, E.g. Moroccan Jews born in Morocco, have a lower incidence of MS than Moroccan Jews born in Israel.

Since these groups have similar genetic susceptibilities to MS, the higher PREVALENCE RATE in the latter is probably due to environmental factors.

Translation: The difference can't be genetic

Our study does not support the effect of latitude on the risk of developing MS since no difference in the PREVALENCE RATE was found between immigrant Jews from Europe/America (E/A) and native-born Jews of European/American origin (I-E/A).

Translation: differences in latitude where people were born did not change prevalence .

Among Arabs, the PREVALENCE RATE was similar to that among immigrant Jews from Asia/Africa. Therefore, we hypothesized similarity in environmental etiologic factors for MS between the countries of origin of immigrant Jews from Asia/Africa and of Arabs communities in Greater Jerusalem.

Translation: Something the same between Jews born in Arab countries and Arabs in Jerusalem is protecting the and it's not latitude

The incidence in Immigrants from europe and America was higher than that of IMMIGRANTS FROM ASIA/AFRICA and Arabs, although this difference did not reach statistical significance.

Translation: something made Immigrants from Europe/America have higher rates of MS than Jewish Immigrants from Asia/Africa or Arabs.

In summation, it might be thus:

If you come from a fish/olive oil country and move to Israel, you're less likely to have MS than someone of the same genetic background who was born in Isreael. If you come from a beer/butter country and move to Isreal, you're worse off than someone of the same genetic background than someone who was born in Israel.

Maybe the Israeli diet is more European than say a Mediterranean country, but has less diary/animal fat than an actual European diet and your risk changes accordingly?