Potatoes (Solanum tuberosum) are a staple carbohydrate source for billions around the world. They boast a storied history from the Incas to the Irish. They seem so harmless, right? Delicious, too! And don’t forget versatile… Well, far from it!
This article will be all about potatoes, mainly about their glycoalkaloids and the toxicity that has been demonstrated in human history, across multiple animal species and via multiple potential mechanisms, plus we won’t even go into its glycemic index… Sound familiar? Potatoes just may be the most dangerous food that westerners eat on a very regular basis – and this is aside from the fact that they’re so often deep fried in pro-inflammatory estrogenic cooking oils. How is this so?
The Darkside of Potatoes
Potaotes and Acrylamide
First of all, while not apparently related to glycoalkaloids, the process of cooking potatoes results in high amounts of the carcinogenic compound acrylamide. In fact:
“According to FDA research, the top three foods with the highest mean acrylamide content were potato based. Products such as restaurant french-fries, oven-baked french-fries and potato chips could pose the highest risk to consumers.”
The whole list of the foods the FDA evaluated is here. As few folks are eating raw potato these days – with the exception of esoteric health fanatics who may blend raw potatoes into smoothies – the acrylamide issue (which is increased proportionally with higher cooking temperatures and with cooking in fats/oils) is a pertinent one right off the bat.
Potatoes and Solanine
While this is not limited to potatoes only, as the FDA list demonstrates, it is very significant with potatoes in particular.
Solanine is the major glycoalkaloid found in potatoes, along with alpha-chaconine. For a short and sweet synopsis of the glycoalkaloids in potatoes, see here. A very important fact is that “the clearance of glycoalkaloids usually takes more than 24 hours, which implicates that the toxicants may accumulate in case of daily consumption.”
This fact alone puts a twist on acute (<24 hours duration) studies done on glycoalkaloid toxicity, as many people eat potatoes everyday, often multiple times a day when all potato-based food additives are accounted for.
Solanine is found in all “edible” members of the nightshade (Solanaceae) family—including tomatoes, potatoes, peppers, eggplant, paprika, Cape gooseberries, goji/wolfberries, and tobacco—and it is well researched and accepted that these glycoalkaloids are toxic to humans and animals in sufficient doses. Even the World Health Organization (WHO) has placed a “safe level limit” on the solanine content of potatoes at 20mg/100g fresh weight. Why did a limit on solanine content need to be created? Because of incidents like this:
“Seventy-eight schoolboys became ill after eating potato at lunch on the second day of the autumn term. Seventeen of the boys required admission to hospital. The gastrointestinal, circulatory, neurological and dermatological findings and the results of laboratory investigations were in keeping with solanine poisoning.”
“Death has occurred in previous outbreaks, usually within 24 hours; but those cases were mainly in undernourished patients who may not have received adequate treatment… Possibly unrecognized mild solanine poisoning may be the cause of many mild episodes of “gastro-enteritis.”
Other references to this issue included Mass poisoning with solanine, Solanine poisoning, Potato poisoning, and A small outbreak of solanine poisoning. So, chalk up a “Black Box” history of potatoes/solanine poisoning people.
Potatoes and Phytoalexins
What conditions create a situation where glycoalkaloids reach toxic levels? They are phytoalexins (defensive antibiotic compounds, anti = against, bio = life, ouch) that increase in concentration in response to real or perceived threat situations to the plant. These threats include:
1. Potato blight—Caused by Phytophthora infestans, an oomycete (water mold) that attacks potatoes and other nightshades.
2. Light and heat—As potatoes are tubers (roots) grow underground in the cool darkness, exposure to the above world (as in heat and light) is perceived as a threat.
3. Mechanical damage (think bruising or rough handling, which wouldn’t happen in the ground).
When Potatoes Become Dangerous (Glycoalkaloids)
Glycoalkaloid content also rapidly approaches toxic levels once the potatoes are greening or sprouting (chitting). It is estimated that 60-70% of the total glycoalkaloids present in most varieties of potato are contained within the peel (aka the supposedly “most nutritious part!”). The big question then becomes, do you think your farmer and grocer know these facts, and how well do you trust them to protect you?
What are the systemic effects of the glycoalkaloids, besides acute poisoning, you ask?
Solanine and alpha-chaconine from potatoes have both been shown to disrupt cell membrane function (1, 2, 3). The negative effects of this disruption may manifest in multiple areas of the body.
In the gastrointestinal tract:
1. Studies on intestinal cell lines (Caco-2) have shown effects upon gene expression and pathways related to cholesterol biosynthesis and growth signaling (1, 2).
2. Exacerbation of irritable bowel disease (IBD) in mice.
3. Necrosis of gastrointestinal tissue in Syrian hamsters (1, 2).
4. Inhibition of human pancreatic proteolytic enzyme activity.
The irritation of the gastrointestinal tract is particularly important in those who are gluten intolerant. In many gluten-free foods, potato starch is a common “replacement” flour—this alone could possibly thwart much of the improvement that one expects when they go gluten-free!
Potatoes’ Effects on the Liver
1. Reduction of liver weight in mice—“The significantly lower liver weights of mice treated with alpha-chaconine and alpha-solanine and the significantly lower %LW/BW [liver weight/ body weight x 100, author] of mice treated with alpha-chaconine suggest that these effects may be due to hepatotoxicity.”
2. Liver gene mutations in pregnant mice.
3. Inhibition of normal human liver cells in vitro.
4. Destruction of normal human liver cells in vitro.
How Potatoes Harm Red Blood Cells
The relationship of glycoalkaloid teratogenicity (birth defect-inducing) has been relatively well studied in animals, including:
- Frog embryos in vitro (1, 2).
- Chicken embryos.
- Toxicity in pregnant rats.
- Birth defects in hamsters (1, 2, 3, 4, 5, 6)
- In vitro inhibition of pre-implantation bovine (cow) embryo development.
As far as I can find, there are no direct studies on the relationship of potato or glycoalkaloid consumption and teratogenicity in humans. With the information above, I wouldn’t let any pregnant woman into *that* study! After looking at the data in animals, who would let a pregnant woman potentially do that to herself and her unborn child?
Important question—If potatoes were not already in the food supply and were introduced today, would you let them in based on those animal studies? I hope not!
There have been enough reviews on the relationship of potato blight to human birth defects, particularly in Ireland during times of potato blight to give one serious pause in regards to consistent consumption of the glycoalkaloids in potatoes (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14). It is quite amazing to me how ZERO precautionary advice is being directed toward potato (and other nightshade) consumption, which has been PROVEN to be birth-defect inducing!
Finally, the potato glycoalkaloids (remember, all nightshades share these compounds!) are potent acetylcholinesterase inhibitors. This drug-like effect has been shown in:
4. And finally, humans (1, 2, 3, 4)
Could this be the main cause of their toxicity and ability to cause physical discomfort? Let’s investigate this further.
Potatoes & Gastrointestinal Health
What are some of the possible effects of acute (short-term) solanine poisoning?
“It is very toxic even in small quantities. The poisoning is primarily manifested by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, nightmare, headache, and dizziness  as well as hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils, hypothermia, and death in more severe cases.”
What are some of the effects of acetylcholinesterase inhibition?
“…adverse effects include gastrointestinal anomalies-nausea, diarrhea, anorexia, abdominal pain, as well as increase in cardiac vagal tone causing bradycardia
Do those sound close enough for you? One other notable action of acetylcholinesterase inhibitors on the neuromuscular junction is that they result in prolonged muscle contraction(s). I’m going to put out some conjecture that the typical “stiffness” found in all types of arthritis, especially osteoarthritis without inflammation, is simply prolonged muscle contraction(s)!
Other Health Issues Linked to Potatoes
Next, imagine what would happen in terms of mechanical wear to any system of moving parts that has increased friction (due to chronically increased muscular tension across joints). Mechanical wear would increase, correct? One mechanism can then explain two issues that are commonly found in arthritis.
For those who plan on eating potatoes (and the other solanine- and chaconine-containing nightshades) anyway, and you’re wondering if there is anything you can do or take to reduce their impact on your system, here are your possibilities—probiotics (especially L. plantarum) and folate (specifically calcium folinate aka folinic acid, never folic acid!).
On the vitamin note, folate is crucial in preventing neural tube defects before and during pregnancy. These malformations include spina bifida (open spine), meningomyeloceles, myeloceles, anencephaly (open skull), encephalocele (gap in the skull) and other anomalies. It also appears to be potentially protective against embryo damage from alpha-chaconine. So, a combination of a folate deficiency and a high intake of nightshade foods would spell real trouble for a developing fetus! If you missed the part regarding the documented history of potatoes and birth defects above, make sure to read that part again!
Other Conclusions Linked to Potatoes
In conclusion, potatoes are just not worth the potential risk(s). If you are going to eat them:
1. Avoid eating the potato peel. Peel potatoes DEEPLY, they should all be of one color when you are done peeling them.
2. Do not eat greened, black, damaged, or sprouting potatoes.
3. If you have any doubt about the length of time (longer is worse) or temperature (warmer is worse) that the potatoes have been stored under, even if not green or sprouting, it is prudent to avoid eating them.
4. The more bitter the potato, the higher the glycoalkaloid content.
5. Pregnant women would do well to avoid all nightshades, potatoes in particular.
6. Realize that combinations of nightshades in dishes will increase the solanine content additively. Example: eggplant parmigiana with a side of gnocchi would be a bad idea.
Instead, you could try your old potato recipes with parsnips or (riced) cauliflower, as anything that can be done with a potato can and has already been done with these two things! Replacing mashed potatoes with steamed & mashed cauliflower equals no toxic glycoalkaloids, less carbs, and more nutrients!
All that and I never even went into the glycemic index and carbohydrate content issue…