As discussed in my prior blog posts, the sulfite molecule appears to be connected to nausea and vomiting in pregnancy and to migraine headaches. Despite sulfiting agents not being allowed by the FDA on most fresh fruits and vegetables, it still shows up in on two commonly-eaten forms of produce: 1) frozen potato products and 2) grapes, on which it is used as a pesticide (against black widow spiders) and fungicide. It appears that organic grapes have much less in the way of sulfites, though, per this 2012 paper--http://www.sciencedirect.com/science/article/pii/S0925521411001633--which says that sulfur dioxide is not allowed as a fungicide on organic grapes.
Let's talk about potatoes for a minute. In May 2016, health news contained a surprising report that potato consumption had been linked to hypertension (high blood pressure) (http://well.blogs.nytimes.com/2016/05/17/potatoes-tied-to-high-blood-pressure-risk). This is especially confusing because back in 2012, a study looking specifically at purple potatoes found that eating them lowered blood pressure (https://www.ncbi.nlm.nih.gov/pubmed/22224463). But when one delves deeper into the finding of the 2016 news, one sees that they looked at consumption of 3 categories of potatoes: 1) baked/mashed/boiled, 2) French fries, and 3) potato chips.
In three prospective cohorts of US women and men, we found that higher long term intake of baked, boiled, or mashed potatoes was significantly associated with an increased risk of hypertension in women, independent of numerous other predictors of risk of hypertension including dietary factors such as whole grain intake and whole fruit and vegetable intake. In addition, higher consumption of French fries was associated with incident hypertension in all three cohorts, whereas potato chip intake was associated with no increased risk.
Did you see that? No increased risk with potato chip intake? Isn't that a head scratcher? What is in potato chips? Potatoes, salt, and lots of oil...but those same things are in French fries! How can potato chips not be linked to hypertension if the other two categories are? What is the difference between potato chips and the other two categories of potatoes? I submit that it is the absence of sulfites and other color preservers in potato chips that is the difference. French fries are permitted to have sulfites (although most fast food chains and frozen potato food manufacturers in the US now instead use disodium pyrophosphate, which is also considered GRAS by the FDA but might pose its own risks, which I'll partially address below) to keep them from turning brown, and mashed potatoes--the most popular choice out of "baked, boiled, and mashed" potatoes in my experience--are usually made from potato flakes that include sodium metabisulfite as a preservative. Potato chips, on the other hand, generally don't include color preserving additives because chip makers fry the chips almost immediately after slicing the potatoes. Here's a video on the process of making potato chips:
Earlier this year, it was noted in a cardiovascular medicine journal that recent findings of sulfites contributing to cardiac dysfunction "should raise a fundamental concern about sulfite preservatives used in wine industry or food" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4880594/). An Iranian study published in 2014 found that ingestion of sodium metabisulfite by rats resulted in an average 43% decrease in heart capillary volume and length (https://www.ncbi.nlm.nih.gov/pubmed/25629268); that doesn't seem like it would be good for the heart or cardiac blood pressure.
As for disodium pyrophosphate, German researchers expressed strong concern in 2012 (https://www.ncbi.nlm.nih.gov/pubmed/22334826) that phosphate food additives, including disodium pyrophosphate, possibly are increasing mortality in those with chronic kidney disease by causing vascular damage, e.g., vascular calcification and endothelial dysfunction. Vascular calcification is a major cause of systolic hypertension in the elderly (https://www.ncbi.nlm.nih.gov/pubmed/22713153), and isolated systolic hypertension appears to be an indicator of worse coronary function than combined systolic/diastolic hypertension (https://www.ncbi.nlm.nih.gov/pubmed/23205754).
I think that the humble potato was unfairly maligned back in May. If the potato itself caused hypertension, potato chip intake should have been associated with hypertension similarly to the other two categories of potato products. I'm still not ready to think of potato chips as "health food," but the evidence seems to excuse them as innocent of causing hypertension and instead points to the food additives being used to keep potatoes from browning.
As a result of research I've done this year--predominantly in peer-reviewed studies and not alarmist, supplement-selling websites--I am starting to lose faith in the FDA's "GRAS" label. Then again, maybe nearly any chemical in large quantities is just bad for us. Talking about moderation, balance, and avoidance of several known-but-popular-and-legal mind-altering substances is not very exciting, but the combination of these principles seems to be a boring, consistent key to maintaining good health.
Update: I just got back from grocery shopping for the family. I started reading labels, and it looks like the "fundamental concern about sulfite preservatives used in...food" expressed earlier this year (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4880594/) was taken seriously. A few months ago, I recall all the non-organic tortillas containing sodium metabisulfite. Now most of the tortillas I looked at do not have sodium metabisulfite. They do still have an additive that, if I recall correctly, is disodium pyrophosphate. And I vaguely recall that a few months ago, I found frozen potato products with added sulfites, but those are all gone now; all the frozen potato products have disodium pyrophosphate in them. This was a quiet ingredient change and hopefully one for the better, as far as Americans' health. However, in light of what I found out today about vascular calcification resulting from too much phosphate (and it's much easier to absorb excessive phosphate from phosphate food additives), I am not unworried by the widespread use of disodium pyrophosphate. Can I please just have regular food to feed my family with?