Holmgren's aim with the book, according to its description, is to help people regain an "appreciation for the earth."
"She's someone who goes straight to the woods behind her home for mushrooms and syrup and heads to her garden for tomatoes and fruits," the book states. "Her cookbook is more than just a book —it's an escape to another realm, a retreat into nature, and a taste of the life she lives."
Holmgren and her publisher, Rodale Books, said in a statement to BuzzFeed News they are "taking the discussions about [Holmgren's] book very seriously."
"We are reviewing its text closely," they continued.
In an email to BuzzFeed News, Holmgren said her cookbook is meant for "adventurous eaters."
"We have personally eaten raw mushrooms and have no had negative experiences," she said.
One recipe that has caused concern is Holmgren's recipe for "Dark ChocolateDipped Fungi." She tells readers to use "two cups of in-season foraged mushrooms," with morel mushrooms being one of the suggested varieties.
The recipe then instructs the reader to brush and wash the fungi, place them on parchment paper, dip them in melted chocolate, sprinkle them with salt and rose petals, and then place them in the fridge or freezer to cool.
The symptoms usually take hold within a few hours of eating the morels raw or undercooked, according to MDCH.
In fact, Richard Pizarro of the Minnesota Mycological Society told BuzzFeed News "as a general rule, no wild mushrooms should be eaten raw."
He said while eating the morels and other edible mushrooms raw will not kill you, "your digestive tract will not be happy." He said this is because some of the mushrooms are hollow and can collect debris, and that the "cell walls of mushrooms are made of chitin."
"Chitin is also in the cell walls of the exoskeleton of crabs, shrimp, and insects," he said. "This is a very difficult material for our bodies to digest and may cause noticeable discomfort. Cooking the morels breaks down the chitin and makes the mushroom more easily digestible."
In addition, it generally takes an expert to safely collect and eat wild mushrooms because some of them can be dangerous, even deadly, and it's easy to mix up species. For example, people looking to collect morels sometimes pick and eat "false morels," instead, leading to potentially serious side effects.
These "false morels" can make you sick if you eat them, according to the Children’s Hospital of Michigan Poison Control Center, which noted that in 2011 several children had become ill from consuming them.
The mushrooms contain a toxin called gyromitrin, which harms the liver. Initial symptoms include "nausea, vomiting, abdominal pain, diarrhea, dizziness, headache, muscle cramps, bloating, and fatigue."
If untreated, the toxin can lead to confusion, delirium, seizure, and coma.
Now, readers of the book are attempting to warn others about the potential dangers. One Amazon commenter wrote they are an "avid forager and chef" and immediately spotted the danger of the chocolate morel recipe.
"That's a pretty big no-no," the reviewer said of the recipe. "Morels need to be cooked first to be safe for human consumption."
"Eating an uncooked morel is against everything that is taught," said another reviewer.
Patton said new research has indicated there are actually fewer glycosides in raw elderberries than in an apple seed.
However, he pointed to a statement from the elderberry cooperative website, which says "some few people seem to be strongly affected by consuming raw elderberries or elderberry juice, where it upsets their digestive system. Why they have a lower tolerance for elderberry is not clearly understood."
Sherrie Hagenhoff, another elderberry farmer who is a member of the cooperative, told BuzzFeed News that the side effects of the berries seem to depend on the amount eaten raw.
She said that she has had people on her farm who have eaten a few of the berries and reported no side effects.
However, she said that "they should be heated or fermented if one wants to consume a larger amount."
Holmgren told BuzzFeed News she has personally made the smoothie recipe containing elderberries for her family, and had "no adverse reactions whatsoever."
"The small amount called for in this recipe is not dangerous," she said.
Philip Stark, a professor at University of California, Berkeley, and the founder of Berkeley Open Source Food, told BuzzFeed News that he is "sure that eating enough tannin will upset your stomach, but I think it would be hard to do, because it tastes pretty harsh."
"If the recipe uses only a few acorns, the tannins might be part of the desired flavor, to give some bitterness to the dish," he said. "But for 'generic' acorns in quantity, I think processing would be needed or the dish would be nasty."
He said most recipes involving acorns call for soaking the acorns for several days to leach out the tannin or grinding the acorns into flour and using boiling water.
Some reviewers also found issue not with the safety of the recipes, but with the recipes themselves. One reviewer said Holmgren's "Minnesota Wild Rice French Toast" was inedible because it instructs only to "soak" the rice, not cook it.
"If you aren’t 1 million percent sure, do not eat it," she said. "Engage with local foraging resources to seek reputable sources within your direct region to give you a basis for your explorations through each season.”
She added that she has the following disclaimer on her website:
“While I strive to be 100% accurate, it is solely up to the reader to ensure proper plant identification. Some wild plants are poisonous or can have serious adverse health effects. I am not a health professional, medical doctor, nor a nutritionist. It is up to the reader to verify nutritional information and health benefits with qualified professionals for all edible plants listed in this web site and any published content.”