Hi aitarg - no worries, I didn't think you were hijacking!
I think it depends on our individual metabolic makeup, which often comes from way back in our ethnic inheritance. Spanish people, who make up a lot of the Mexican gene pool, also seem to eat quite a lot of pulses, and I believe pulse eating was common among the original South and Central American inhabitants. As mentioned in my post, the doctor did say pulses only had this effect on people who were susceptible.
Not that it's unheard of for different ethnic groups to have different dietary intolerances. After all, Chinese, Japanese, Thais, Vietnamese etc. are lactose intolerant to a large extent. That's why you seldom see dairy products being used in their cuisine. The northern Chinese races are the exception to this rule. They're the Mongolian strain, more like Tibetans, and have evolved to eat a lot of dairy products. Not sure whether native Americans are more lactose-intolerant than others. They were originally from similar stock, but again are more the Mongolian type so they're probably OK.
I've always understood it's an evolutionary effect. The ability to digest dairy foods would have been an advantage in ethnic groups who originated in areas where there wasn't much meat available, or the terrain made hunting more difficult. In those circumstances, the ones who couldn't digest milk products would have tended to die young from protein deficiency. Milk digestion would also have been an advantage in northern climes, where there's less sun, as milk is high in vitamin D.
It's a phenomenon that can be found all over the world, with various food groups and other attributes. An example is the sickle cell anaemia gene, which tends to be widespread in people of sub-Saharan African descent. This chronic disease itself is very nasty (I once saw a sickle-cell crisis as a student nurse) and tends to cause significant shortening of life, so you'd expect it to have died out. However, when only a single copy has been inherited from one parent, the gene has a strongly protective effect against malaria... which is, of course, endemic in sub-Saharan Africa and is itself a major killer.
Likewise, races who originated in climates where there's a lot of sun evolved to have more melanin in their skin and eyes, to protect them from the harmful rays of the sun. Light-skinned people would have had an advantage over darker-skinned ones among races who developed in northern climates (e.g. Scandinavians), as they would have been able to synthesise more vitamin D from the limited sunlight available.
Nowadays, of course, we're all mixed up together, so these differences become less significant. I have (well, had!) dark hair, nearly-black eyes and a sallow skin in spite of being born in relatively sunless Britain, as one of my great-grandmothers was Indian. I'm fascinated by the subject of genetics and evolution, and would love to have studied it.
OK, that's enough or I'll get taken down for being off-topic!