CAREFUL, COULD STILL BE DANGEROUS...
Just because it’s “natural” doesn’t mean it’s healthy. There are plenty of plants and animals that can be deadly to humans if consumed. Examples include plants like wolfsbane, horse chestnut, belladonna, hemlock, wild carrot, common ivy, European holly, daffodil and oleander, as well as animals like many toads and frogs, some fish (ex. barracuda) and even some birds! And thanks to COVID we're all now aware that eating bats can be problematic (that's true whether the virus came from a lab or not... but let's not go down THAT rabbit hole!).
Of course most of these items will never find their way into your local grocer. While less deadly, there are many items found in the typical American grocery store that can cause acute or sub-acute allergic reaction and/or inflammatory response. If severe enough, we call these food allergies. If less severe we call them food sensitivities or intolerances. Regardless of the severity, one of the pathways to healing and optimal health is eliminating or reducing our consumption of these items.
WHEN THE ITEM ITSELF IS PROBLEMATIC, REGARDLESS OF HUMAN MEDDLING
Some may ask “But WHY are people having an adverse reaction or intolerance to these items?” The answer depends on the item and the individual. On one hand there are certain natural items that, regardless of how well they were grown, raised or processed, the raw material proves problematic for a notable percentage of people. Items here might include things like…
· Unfermented soy (problematic for some because of the plant phytoestrogens)
· Beans and legumes (possibly due to so called anti-nutrients like phytic acid and oxalates, and perhaps lectins)
· Cashews and pistachios (members of the poison ivy family, sometimes they contain the allergen urushiol)
· Mangoes (also members of the poison ivy family)
· Nightshade vegetables (includes eggplant but also peppers and tomatoes)
· Shellfish (some are reactive to tropomyosin proteins; reactivity here is likely exacerbated by the rudimentary digestive systems and respective diets of shellfish)
· Pork (in part due to pork's higher likelihood of significant parasitic load in its muscle meat)
· Cane sugar (high intake can lead to blood sugar problems, inflammation and glycation, which can damage soft tissues)
· Cover fat from red meats (as distinct from marbling/inner muscular fat)
Personally, I try to limit consumption of all of these items, with the exception of beans and legumes (the plant-based proteins, high fiber content and presence of several essential micronutrients in beans and legumes outweighs concerns over phytic acid, oxalates and lectins, at least for me personally).
Here I should also mention tree nuts (low in water content, tree nuts as a category can be more difficult to digest, increasing risk of adverse reaction) and fish with fins and scales (while some have suspected iodine may contribute to allergy here, the clinical data points to parvalbumins, a common protein found in certain fish). I find certain tree nuts (ex. roasted and salted almonds) quite healthy in moderate amounts, and wild-caught fish (ex. salmon, most white fish, etc.) tends to be one of the healthiest animal protein sources on the planet.
WHEN THE ITEM IS MADE PROBLEMATIC DUE TO HUMAN MEDDLING OR ADVERSE CHANGES TO
A PERSON'S DIGESTIVE SYSTEM
Other items are made problematic because of issues related to modern farming, animal husbandry and/or food processing methods, as well as changes in an individual’s digestive system and gut flora due to factors like parasitic or pathogenic microbial infection, use of certain digestive system-damaging medications (ex. antibiotics, NSAIDs, acetaminophen/Tylenol, opioids, etc.) or some other gastrointestinal trauma (which could include chronic poor eating habits). Food items here might include…
· High gluten or gliadin-containing grains (found in most commercial wheat, and to a lesser degree in spelt, rye, barley; selective hybridization has led to cultivars with much higher gluten/gliadin content than those from centuries ago; some also point to persistent pesticide residue [ex. glyphosate])
· Oats (often contain gluten due to processing methods)
· Soy (more than 90% of soy grown in the U.S. is GMO)
· Peanuts (peanuts, being grown in the ground, may be more prone to mold, and many peanut fields are sprayed with fungicides that are neurotoxic to people)
· Sprouts (can easily grow mold if not consumed quickly after sprouting)
· Corn (more than 90% of corn grown in the U.S. is GMO)
· Some commercial table salts (often contains anti-caking agents)
· Non-organic eggs (reactivity may be due to proteins like albumin; organic eggs and eggs from hens raised on pasture typically carry less of a risk of allergy than conventional eggs)
· Farm-raised fish (more susceptible to parasites in muscle meat due to fish farming conditions)
· Some types of red meat (usually due to poor marinating and tenderizing methods which make tougher cuts harder to digest; there’s also the issue of bovine hormones, as well as the way that “feedlot cattle” are raised and brought to slaughter [unnatural high carb diet, antibiotics, crowded & unsanitary living conditions, etc.])
· Many cow’s milk dairy products (due to problems with lactose and casein [specifically A1 beta-casein protein], possibly exacerbated by issues like GMO grains being fed to cattle for generations, bovine hormone and antibiotic use, pasteurization and homogenization methods, etc.)
· Canola oil (a GMO rapeseed hybrid)
· Certain types of alcohol (due to added sulfites/sulfur dioxide, pesticide residue [Roundup/glyphosate], etc.)
And then there are problematic foods that aren't typically found in the American diet but are found elsewhere (like lupins, a legume belonging to the peanut family that's popular in Mediterranean and Latin American cuisine) and other foods a smaller minority of people have problems with (ex. some seeds like sesame). [1-5]
THAT'S A LOT OF FOOD TO CUT OUT!
WHERE SHOULD I START?
Wrapping your head around all of the previous info can be difficult to say the least, which is why I encourage most of my clients to at least start with "the big 3." Here we're talking about...
· Most dairy (exceptions often include butter and may include no/low lactose and no/low A1 beta casein protein foods like sheep cheese, goat cheese and possibly Greek yogurt)
· Unhealthy sugars & sweeteners (ex. cane sugar, refined sweeteners, artificial sweeteners)
Of course if you know you have adverse reactions to a food other than these you'll want to prioritize avoiding that item as well (for example, allergies or adverse reactions to peanuts, tree nuts and shellfish tend to be more common among children than other allergies, sensitivities and intolerances).
PROBLEMS WITH WHEAT & HIGH-GLUTEN FOODS
If it seems like the health conversation around wheat and gluten has gotten louder and louder in the last 15+ years, there are good reasons for it.
First there was Dr. Alessio Fasano’s groundbreaking (and at the time controversial) 2003 study published in JAMA’s Internal Medicine journal which showed that celiac disease was present in around 1% of the U.S. population, a rate that was 5-10x higher than it was in the 1950s and 5-10x higher than what many researchers thought it was at the time (celiac disease is an inflammatory bowel disease that is characterized by severe allergy and intolerance to products containing gluten). 
Next came the Food Allergen Labeling and Consumer Protection Act (FALCPA), a 2004 law that became effective on January 1st 2006 which requires all food labels in the U.S. to list if any of the eight major food allergens are present in the item (wheat is one of the eight major food allergens). 
Then in 2011 came the publication of the highly successful (and still quite controversial) book Wheat Belly by Dr. William Davis MD. On the heels of that came another hugely popular book, Grain Brain, by Dr. David Perlmutter MD, which was published in 2013.
And more recent research seems to confirm that the prevalence of gluten-related digestive issues is only increasing. In a study of more than 1300 infants published in 2017, gastroenterologist Dr. Edwin Liu found that the celiac disease rate had jumped to 3%. 
And it’s not only celiac disease that’s directly linked to gluten. Non-Celiac Gluten Sensitivity (NCGS) is another condition that appears even more common than celiac, with prevalence rates as high as 13%. In other words, recent research suggests that as many as 1 in 7 Americans have some kind of gluten-related medical condition, either celiac disease or NCGS.
But why? Why have gluten-related conditions increased? I would suggest 3 primary factors…
1. Increased recognition of the conditions, including their symptoms, by healthcare professionals and patients alike
2. An increase in the gluten content of most commercial wheat varietals over the last 100+ years. Through the 20th century, farmers were financially incentivized to grow wheat varieties higher in gluten, in large part because of the reaction baker’s yeast has with higher gluten dough (it produces a more airy, fluffy, less dense baked good). Consumers pay more for taste, which means higher gluten wheat fetched a higher price.
3. Negative trends in the general condition of the gut microbiome of many Americans. A dramatic and widespread increase in antibiotic use (which started in the late 1940s) has had a negative effect on the amount and type of beneficial bacteria in people’s intestinal tract. Add to this the adverse effects of other medications (ex. NSAIDs, opioids, etc.), an increased number of C-sections (shown to rob the newborn of gut microflora bestowed by mother through a vaginal birth), gut reactivity caused by persistent pesticides (ex. glyphosate), and major increases in chemical additives to the food supply and you’re left with intestinal tracts that are much more sensitive to problematic food proteins and food-borne allergens, antigens and pathogens. [9-11]
PROBLEMS WITH MOST DAIRY,
INCLUDING LACTOSE & A1 BETA-CASEIN PROTEIN
So what makes most commercial dairy problematic? A few things…
1. Lactose. Many adults lack the enzyme needed to break down lactose, the primary sugar in liquid milk. For people like this who consume a notable amount of lactose, adverse symptoms can include acid reflux, bloating, gas or abdominal pain.
2. Casein. Casein is one of two proteins found in liquid cow’s milk (the other is whey). Casein is about 4x more prevalent than whey in milk and is the more slower digesting protein. For individuals with under-functioning digestive systems, this difficult to digest protein can cause some problems (note that one relatively popular diet out there is the GFCF diet or the Gluten Free, Casein Free diet). 
3. A1 Beta Casein Protein. What the heck is that you say? A1 beta casein protein is a type of casein protein found in notable amounts in the vast majority of commercial cow’s milk (other classes of casein protein include alpha casein and kappa casein). If you’d like to deep dive into this topic I recommend a relatively obscure book called Devil in the Milk by Keith Woodford, published in 2009. In the last few years A2 cow’s milk has started to hit the shelves, in part because of an increased awareness of digestive and health problems related to A1 milk.
4. Homogenization. Homogenization is a process that mechanically breaks up cream and fat globules in milk so that the fat is more evenly distributed through the liquid (instead of the cream rising to the top). Some researchers believe this process may denature or adulterate the dietary fats in the milk, which may contribute to allergy, intolerance and disease.
5. Pasteurization. Named after French biologist Louis Pasteur, pasteurization involves heating up milk (often to around 160 degrees F for 15 seconds) in order to destroy certain disease-causing pathogens that may be present in the milk. For the modern era, pasteurization of milk began in the 1880s and was effective at destroying certain disease-causing microbes, microbes that, because of unsanitary dairy practices, were contributing to milk-borne illnesses. From that time to now there has been much debate as to whether pasteurization denatures or destroys certain natural molecules in milk, making pasteurized milk harder to digest and increasing risk of allergy or intolerance. While illegal in a few states, the sale of raw unpasteurized milk is currently legal in more than 40 states. Check out www.realmilk.com for more information on raw milk. 
Aside from things like lactose, casein, homogenization and pasteurization, there are also the issues of bovine growth hormones, GMO corn and soy feed and antibiotic use/overuse, all of which influence the quality of the milk produced and various dairy products made from that milk.
My advice to most people is to avoid cow’s milk products, with the exception of grass-fed butter or ghee (clarified butter). That said, the science is clear that dairy is the best source of bioavailable calcium, so I do recommend people consider a diet that includes small amounts of goat or sheep’s milk cheese, in order to obtain adequate amounts of bioavailable calcium (2-4oz of this kind of cheese/day = 600-800mg calcium/day).
UNHEALTHY SUGARS, INCLUDING CANE SUGAR
AND REFINED SWEETENERS
And the last of the “big 3” is unhealthy sugars, which includes cane sugar and refined sweeteners like high fructose corn syrup. While more controversy and disagreement exists among researchers and scientists regarding wheat/gluten and dairy, the scientific community is pretty well unified on its stance toward sugar and refined sweeteners- the less, the better.
In the early 1800s Americans ate very little sugar. From the 1820s to 1840s the average American ate less than 10lbs of sugar a year. But over the last 200 years Americans have fallen more and more in love with (addicted to?) the sweet stuff. By 1880 Americans were averaging 30lbs a year in consumed sugar. By 1900 it was over 40lbs a year and the 1920s found Americans consuming 80lbs of sugar each year. Sugar consumption temporarily leveled off during The Great Depression, WWII and the 1950s before climbing again during the mid and late 1950s. By the late 1960s Americans were shoveling down an alarming 100lbs of sugar a year and another 15lbs of corn-based sweeteners. By 1980 Americans had breached the 120lbs a year threshold (85lbs of sugar, 20lbs of high fructose corn syrup [HFCS] and another 15lbs of other corn-derived refined sweeteners). Finally, we peaked in the year 2000 at more than 150lbs of sugar consumed by the average American, which included 65lbs of cane sugar, 65lbs of HFCS and another 20lbs of other corn-based refined sweeteners. 
Thankfully annual sugar consumption per capita has dropped the last 15-20 years. In 2017 Americans “only” consumed 127lbs of sugar. Even with cutting more than 20lbs a sugar per person per year the U.S. is still far-and-away the #1 sugar consuming nation in the world. The average American consumes more than 126g of added sugar each day. The good people of Germany and Netherlands are next at 102g/day. To put those numbers in perspective, the American Heart Association recommends a MAX of 25-36g/day for men and women. Current consumption rates are 4-5 TIMES that amount. So where is all of this added sugar coming from? The top source at 45% is (drumroll please)… sugary drinks, which includes soda, energy drinks, sports drinks and fruit drinks (grain-based desserts are #2 at 10%). [15-16]
As many of you are already aware of, excess sugar consumption is linked to just about every major disease that plagues modern America, including cardiovascular disease (kills >750,000 a year), cancer (kills >600,000 a year), diabetes, Alzheimer’s, obesity, arthritis and joint pain, liver disease (including fatty liver) and premature aging. 
A number of documentaries and books are available on this topic, including filmmaker Damon Gameau’s That Sugar Film (released in 2015) and books like William Dufty’s Sugar Blues (first published in 1986) as well as more recent works like Gary Taubes’ The Case Against Sugar (2016) and Dr. Richard Jacoby’s Sugar Crush (2015).
1 https://farrp.unl.edu/informallbig8 (8 common food allergies, including soy, shellfish, wheat, peanuts, eggs, milk, tree nuts, fish)
2 www.ncbi.nlm.nih.gov/pmc/articles/PMC4414527/ (2015 review of allergy basics; includes discussion of wheat, peanuts, eggs, milk, tree nuts, fish [doesn’t include soy, shellfish])
3 www.ncbi.nlm.nih.gov/pmc/articles/PMC5123910/ (2016 review of food allergies; includes discussion of soy, shellfish, wheat, peanuts, eggs, milk, tree nuts, fish)
4 www.ncbi.nlm.nih.gov/pmc/articles/PMC5940350/ (2018 review of food allergies; includes discussion of soy, shellfish, wheat, peanuts, eggs, milk, tree nuts, fish)
5 www.ncbi.nlm.nih.gov/pmc/articles/PMC6723663/ (2019 review; discusses specific components of foods [often a protein] that trigger allergic response)
6 https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/215079 (Fasano's 2003 study on celiac disease prevalence)
8 www.ncbi.nlm.nih.gov/pmc/articles/PMC5533620/ (2017 study showing celiac rates at 3%)
9 www.ncbi.nlm.nih.gov/pmc/articles/PMC5725362/ (2018 review on antibiotics adversely altering gut flora and microbiome)
10 www.ncbi.nlm.nih.gov/pmc/articles/PMC4831151/ (2016 review on antibiotics adversely altering gut flora and microbiome)
11 www.ncbi.nlm.nih.gov/pmc/articles/PMC4235701/ (2013 review of NSAIDs adverse effects on intestinal health)
12 http://milkfacts.info/Milk%20Composition/Protein.htm (discussion of casein & whey proteins)
14 https://www.bloomberg.com/opinion/articles/2018-10-11/americans-cut-sugar-intake-in-decline-worth-celebrating (Americans cut 20lbs sugar/yr over last 15-20 yrs; still #1 in world)