Seems as if there is no food ingredient that is really safe, always ? Something that can be trusted to be healthy whatever.
"One kale sample reported thallium at 1.14 ppm, nickel at 20 ppm, and aluminum at 120 ppm. (As has been widely reported, aluminum is often suspected as a cause of both autism and Alzheimer’s disease.)"
It's pretty controversial claim that aluminum is related to Alzheimer's disease http://www.webmd.com/alzheimers/guide/controversial-claims-r...
"Often suspected" is a deliberately misleading and alarmist way to present the current scientific data on the relationship between aluminium and Alzheimer's disease.
Sourcing from your back yard (and to a lesser degree, a single farm; and to a still lesser degree a single geographic region) means you're not eating veggies grown in a variety of soil compositions, even if you are eating a variety of plant species.
The most extreme way this can fail (that's common enough to note) is if the soil in your back yard is high in lead.
Compelling.
What are the odds things would turn out any different with the rest of the population of Marin?
My layman's understanding is that the nutrient density of the soil is equally (if not more) important to the "healthiness" of vegetables than the particular species of plant itself. It's almost common sense, on some level.
