I couldn't help but notice that the article didn't make any distinction between fresh, canned, and frozen veggies (or dried, in the case of fruits), types of fruits and veggies, or preparation methods of fruits and veggies. You could be eating 470 g of bananas daily, or 470 g of iceberg lettuce - huge difference in nutritional value (whether or not it's accessible or detrimental in your particular digestive system). Or you could be eating 470 g of vegetable soup, and assume the water in the can should be counted as part of your veggie intake. Or you could be eating frozen dinners but since the frozen dinner has veggies and a fruit based dessert in it, you count the weight of the entire frozen dinner as fruit and vegetable intake.
If all you're eating is fresh veggies, mostly high moisture veggies (iceberg lettuce will weigh a lot more for the same volume of leafy greens than fresh spinach), and considering high moisture zucchini to be on the same anti-stress nutritional level as potatoes (considered by the USDA to be in the veggie category), or potato chips (made from the potatoes that are considered to be a veggie), corn (actually a grain, but found in the produce dept, and sold as if it's a veggie), raisins (dried fruit - weighs a lot less than whole grapes, so a huge difference between the metabolic and dietary effects of 470 g of grapes vs 470 g of raisins)... well the list can go on and on. Not all veggies and fruits are created equal, and they're certainly not all being consumed in ways that contribute to their nutritional equality, so I can't see how they could possibly contribute to anti-stress in the same way either.
Merely stating that 470 g of fruits and veggies each day is some kind of anti-stress threshold is very misleading, even for those who have no digestive, metabolic, or autoimmune issues associated with eating that much fruit and veggies.
Of course the fact that it says nothing at all about how this information was gathered - based on actual records of food consumed each day, or recall food diaries that could be wildly different from actual intake over the course of months or years.
Also, what do they consider to be "less stress"? And is that based on the individual's assessment of their stress level? Or on some analyst's perception of what is more or less stress?
Someone who is single, earning more than enough money to support themselves comfortably, has a nice home, no daunting expenses, a job that they love, no health issues (basically life is rosy) - that person is going to have less stress overall than a single mom with 5 kids to support, in a crowded, sub-standard living situation, on a low income, working a job they hate because there's nothing else she can do when needing to be home as much as possible with her kids, has chronic health issues, and is dealing with an ex who ignores court ordered support payments (basically life is one big stress piled on top of another). How can you possibly compare eating a certain amount of fruits and veggies (which could be in a myriad of forms) each day and say that one factor somehow has more to do with their perceived stress level than whether their live is is rosy, or life is one stress piled on top of another? Or anything in between?
There's also the factor of people who have always been extremely stressed, whether there's really anything wrong or not ("If you don't think you have anything to worry about, you're obviously overlooking something") as compared to people who have never allowed the everyday stresses or even suddenly high stress situations to rule their lives ("Nobody ever changed anything by worrying about it. Worry is a waste of time and effort").
I dunno, it just seems like they're trying to push more fruits and veggies, without any real description of what that means other than "470 g daily", and without providing much at all to support the conclusion that people who eat 470 g of fruits and veggies are less stressed.