I read The Botany of Desire by Michael Pollan (2001, Random House) a year or so after it came out. The book’s four sections detail the relationship between humans and four charismatic plant species. The book describes how plants use their many seductive powers to harness humans to ensure that they (the plants) spread far and wide. Pollan noted in the early pages that flowering plants have been doing this—manipulating animals of which humans are just one species—for most of their 145+ million year history. As a paleobotanist, I would argue that plants have been manipulating animals for even longer, dating to the earliest seeds and perhaps beyond.
The Botany of Desire traces the evolution of apples from tiny, bitter bird dispersed things in China to the gigantic, sweet and fleshy fruits loved by large mammals in Central Asia. And, of course, being large mammals with a sweet tooth ourselves, we couldn’t resist carrying apples out of Asia and around the globe. The second species, tulips, were sought for their beautiful blooms and Pollan recounts the tulip bubble in 17th Century Holland. Marijuana is a third species that has so enticed us that we grow it in vast greenhouses where it is pampered like a purebred lapdog in the parlor of a queen. But the shocker for me was potatoes.
Potatoes came out of the Andes where they remain a diverse crop of high nutritional value. Potatoes came to Europe with the returning Spanish explorers and became a specialty food for the rich. Fast forward to the late 17th Century and potatoes had become an important supplemental food for the whole population, particularly in high latitudes where it was both hardy in the cold and stored well over winter. Potatoes remained an important component of the European diet but only attained staple status in Ireland. The potato’s transition to a staple food in Ireland happened gradually during the late 18th and early 19th Centuries when it first became a winter staple. Then, high prices pushed landlords to export most of Ireland’s grain, leaving their tenant workers to eat potatoes year round. This was fine, as potatoes combined with butter and milk make an almost perfect human diet. And the move toward a single, well-adapted and high yield variety—the Irish Lumper—sealed the fate of the Irish nation.
In 1843 or 1844, Phytophthora infestans arrived. Phytophthora infestans is an oomycete, a so-called “water mold”, that infects the potato plant and causes it to wilt overnight in a disease called blight. The oomycete originated in Mexico, where potato is native, and spread to domestic varieties throughout North America causing local crop failures. That was unfortunate, but since potatoes were still a luxury food in North America, no crisis followed. Blight remains endemic in North America. It is not clear how Phytophthora infestans arrived in Europe, but it was likely that ships that sailed from Baltimore to Ireland carried infected potatoes. By 1845, crops were failing in Ireland. By 1852, a million people had died of famine and a million more had left Ireland, mostly for North America.
Phytophthora infestans is only one of many disease organisms that plague potato. In fact, popular modern cultivars are so prone to disease that, when grown in monoculture, the field has to be nearly sterilized with microbicides, herbicides, insecticides and fungicides before it will yield a crop. And the very nature of the potato as a storage organ means that the plant socks away all these chemicals in its plump and tasty tubers. In Botany of Desire, Pollan reported on a farmer in Idaho who will not feed the potatoes he grows to his own family because of the toxic cocktail in which they are grown. Instead, his children eat organic potatoes grown in the manure pile in back of his barn. This farmer is no physician or food toxicologist. He’s just using good common sense.
Reading that chapter, I recalled an old episode of the CBS news magazine 60 Minutes in which the toxicity of an average market basket was analyzed. Sure enough, potatoes came out as a key offender for a variety of pesticides. That was followed by an episode of Jean-Michel Cousteau’s Ocean Adventures in which Cousteau was interested in ocean pollution so had he and his team tested for bioaccumulating toxins—those that are consumed by marine creatures and build up in the body the higher up the food chain one goes. To everyone’s shock, the young son of one of the team’s biologists shot off the chart. The kid ate a vegetarian whole foods organic diet as prescribed by his greenie mom, so sea food was not to blame. There were tears and general panic at the test results until grandma came forward to admit that when mom was at sea with the team, kid liked to go out for french fries. Cut to stand up. And this isn’t just a worry of the popular media. These reporters were following a large primary scientific literature showing that a variety of common pesticides including malathion (an insecticide), HCB (hexachlorobenzene, a bioaccumulating fungiside), lindane (an insecticide) and p,p-DDD (an insecticide metabolite of DDT and mammal carcinogen) persist in conventionally grown potatoes. The good news is that peeling, washing and boiling helps to remove pesticide residues (Soliman, 2001) but, well, YUCK! Pollan had me off potatoes for a couple of years until organic versions made it to my corner of New York. I’ll take my chances with BT, thank you very much, and I don’t really care how it got on or into the spuds.
So where’s the problem? I have a “safe” organic option. The problem is that a bag of potatoes came to us through the food bank. These are quite conventional and I’m sure that they carry the typical toxic load. We peel and soak and boil, so that helps. But I felt the twinge of guilt feeding them to my children, who gobble them up as they do all forms of starch. The twinge became a conversation as we prepared home-made oven “fries” the other evening.
“What should I do with these potatoes? Does peeling help? Are they really okay to eat?” asked David.
My response was flip but 100% true: “Well, most people eat them don’t they?” The implication is “of course they are safe” but the reality is that they are laced with stuff that we really shouldn’t be putting in or on our bodies.
Organic potatoes are a tiny niche market. The vast majority of spuds produced and consumed in the United States, including every single one served with fast food and in school cafeterias, and 99.99% of those served in restaurants, are conventionally produced and laced with bioaccumulating chemicals. None of the materials sprayed on those spuds are particularly toxic to humans, especially at the concentrations found in the final product. This stuff is regulated, after all. But some of the chemicals do build up in our bodies over time and some can mutate our genes in ways that may cause trouble down the road. For me, who is more or less half way done with the body, it may not matter too much. But for my children the stakes feel higher.
We did prepare and eat the potatoes. I’m being paranoid, of course. One sack of laced spuds will not shorten anyone’s life. The real theme here is “most people eat them” all the time. And we wonder at rising cancer rates and developmental changes and the increase in this or that syndrome. And frustratingly, there is no way to conduct research on cause and effect because, well, “most people eat them” a lot. There is no control group. And more importantly, the hypothesis that we can blame all of our cancer woes on a single food is, well, silly.
But let’s say that we all decided that we didn’t want those chemicals in our food. The plant diseases don’t go away and the alternatives—integrative pest management—usually mean scaled down production, scaled way down. That means higher prices and potatoes exit the SNAP shopping basket. They become, as they began, a boutique food for the wealthy…like organic potatoes are now. A significant source of cheap plant calories, vitamins and minerals disappears from the diet of the masses—and the poor who need high quality food as much or more than the rest of us. Maybe we shouldn’t mourn the demise of fries. But mukimo is another story.
Soliman, K.M. 2001. Changes in concentration of pesticide residues in potatoes during washing and home preparation. Food and Chemical Toxicology 39:887-891.