Lesson that single foods can't replace veggies, fruits, or other elements in a truly balanced diet and yet they also aren't the same as in the past: dairy. There is a certain fishy and quite ambiguous label that implies rBGH-laced milk is the same as that without the use of those bovine growth hormones. 
The mid-1800s already echoed modern-day conventional milk production with the development of whiskey-swill feed. This toxic milk turned blue and had taste, color, and more additives to "fix" it a bit. The World War I era had a backlash which mandated pasteurization in reaction to this nasty kind of milk, without much mention that milk used not to be quite so fake. There was even and early "certified clean" raw milk certification which acknowledged there were better ways to produce dairy yet got swept away(1).
Today, modern dairy cattle receive hormones and lots of other chemicals in feed and the general process... even yield prescription drugs in the milk. Yes, there are plenty of other ways to get calcium than milk(2). Yet, drugs are meant to produce some effect on someone, as well as side effects. Those weren't in the food of the past.

Sources:
1. http://www.mylittlehomestead.com/historyofrawmilk.html
2. ​http://www.seattleorganicrestaurants.com/vegan-whole-food/chemicals-antibiotics-in-milk-glyphosate-toxic-to-dairy-cows.php

Standard diet understanding, of course, will beget a quick-fix mentality if we stick to foods which don't serve our bodies and ignore the boatloads of essential nutrients in foods right under our noses. This and that little isolated nutrient in supplement form tend to prevail... and quick little flu and other shots.
Those shots predominately have far more than deactivated virus or what-not. They may contain neurotoxic metals like mercury and aluminum; toxic sweeteners (how weird!); doses of formaldehyde certainly well before many will die; and other little surprises which may cause fever, vomiting (I had that!), hives, and salmonella(1).
Superfoods are super when we incorporate many sorts of them every day as the basis of our FOOD with immune boosting as just one little goal. So many fruits have Vitamin C and antioxidants [and far more great stuff]. Selenium is in egg yolks and Brazil nuts(2).
We eat anyway. Let's lay aside pitfalls of our nutritional journeys so we lay the groundwork we need most! My family thrives on the best superfood technology ever which provides us with superior absorption and density of nutrition to what we could buy and whip together on our own - please contact us for more info!

Sources:
1. https://www.naturalnews.com/035431_vaccine_ingredients_side_effects_MSG.html#
2. ​http://www.eatingwell.com/article/8762/healthy-immunity-diet-guidelines/

We learned about the basic food groups in school and (to some degree) a basic concept that we need a bunch of different nutrients every day. Yes, some foods that happen to be categorized under these headings are in reality worse than others overall.
Yet, there are always these and those fads which deny the needs for certain nutrients, basic food groups, and/or relative balances between them(1). They may also blame certain bodily processes, hormones, etc.  for weight loss/gain or other issues in exclusion of many other contributing natural processes and promises "the" thing that will "cure" or "mitigate" that issue out of context(1).
So many diets also ignore the need not to eat sometimes and deal with accumulated little saboteurs which enter our bodies and weigh us down - a periodic fast(2). A specific supported form that nourishes with natural nutrients and helpful botanicals and that I and my family utilize is especially effective(2) - please contact us for more information!

Sources:
1. https://my.clevelandclinic.org/health/articles/9476-diets-fad-diets
2. http://www.isagenixhealth.net/why-cleansing-with-isagenix-works/

My personal health journey very much capitalizes on being proactive about the link between brain and digestion. We may know that our brains will die pretty quick without oxygen, but what about when processing point of nutrients for the whole body is out of whack?
A pet-peeve mentality exists around major foods - some people just can't handle this or that and have allergies to them. Major allergenic foods like corn, soy, and wheat tend to feature a pesticide that works by  inhibiting the shikimate pathway, a process that processes amino acids, thus disrupting digestion and encouraging intruding pathogens to grow: glyphosate, brand name Roundup(1). I certainly consumed a lot of pesticides in the first 15 years of my life and sure got my doses of candy and soda with corn syrup back in the day. The dairy I was said to be allergic to in infancy was grain-fed, had artificial hormones, you name it.
Almost every autistic person is believed to have gut issues where they leak nasty things into their bloodstreams that assault - their brains(2). No matter who we are, our brains will thank us for being proactive about our guts!

Sources:
1. ​http://www.anh-usa.org/half-of-all-children-will-be-autistic-by-2025-warns-senior-research-scientist-at-mit/
2. ​https://www.scientificamerican.com/article/gut-bacteria-may-play-a-role-in-autism/