Oxalates are a mixed bag, and are considered an "anti-nutrient", by binding nutrients and preventing absorption during digestion. Ex: Spinach has loads of calcium, but raw, is a poor source of calcium due to oxalate content. However, cooking foods with oxalates in them breaks down the oxalates and frees up the nutrients and partially prevents the anti-nutrient effect.
Excessively high Vitamin C diets (don't supplement to ridiculous amounts, some people do), possibly in combination with low calcium diets (calcium in the body is used to flush oxalates out), can lead to increased risk of kidney stones in diets with high oxalate content. Having a genetic mutation that leads to increased risk of kidney stones can add to this. Please note, there is a lot of ifs in that statement I just said, each one of them independently increases risk, but generally do not reach problematic levels unless you do (or have) more than one.
You shouldn't really worry about oxalates, just don't consume oxalate containing foods in absurd amounts, unless you already are at risk of forming the kind of kidney stones effected by oxalates, then you probably should switch to a low oxalate diet. As usual, talk to your doctor if you think you might be at risk.
The report in question is just that-- a case report. It is not scientific in any sense. There's no way to establish causality here. All we can tell is this guy had oxalate kidney stones, and he also drank a lot of tea. That's it.
Controlled studies have found lower rates of kidney stones in tea drinkers:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412450/ - Daily Green Tea Infusions in Hypercalciuric Renal Stone Patients: No Evidence for Increased Stone Risk Factors or Oxalate-Dependent Stones
- https://www.acpjournals.org/doi/10.7326/0003-4819-128-7-1998... - Beverage Use and Risk for Kidney Stones in Women
- https://academic.oup.com/aje/article/143/3/240/77956 - Prospective Study of Beverage Use and the Risk of Kidney Stones
- https://pubmed.ncbi.nlm.nih.gov/23676355/ - Soda and other beverages and the risk of kidney stones
And why iced tea in particular? That idea seems to have come from one single doctor, who said in an interview once that cold tea encourages people to drink more of it, versus hot tea. Again, no evidence, just cuz he thinks so:
https://www.medicalnewstoday.com/articles/248633#2
EDIT:
The authors of that case report somehow miscalculated the oxlate content of tea by a factor of ten. They claim that tea contains 50-100mg of oxalate per 100 ml. The actual content is about a tenth of that. Much less than a host of other common foods. And of course their report makes attempt to ascertain the rest of his diet.
This is essentially fake health news.
This advice should be taken very carefully. The amount of oxalate removed is highly dependent on the cooking method and the food in question. Furthermore, some foods like spinach remain very high in oxalates in comparison to other foods even after preparation. Finally, cooking is not effective at reducing insoluble oxalates. It's probable that insoluble oxalates are less problematic, but I don't know of any good data showing they are harmless.
The translation is that in actual humans, oxalate metabolism possibly isn't that important to cardiovascular outcomes on average. But it is probably important for some people.
https://kidneystones.uchicago.edu/how-to-eat-a-low-oxalate-d...
What is meant by that though? Radio-labelling experiments do show that some dietary fat ends up as stored in fat cells.
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2362....
Cruciferous vegetables seem more a feature of the Mediterranean diet or standard diet?
So I am assuming that the WD is lower in the necessary precursors for glycine production.
Also, I'm assuming that glycine ingested directly would just be metabolized before being used in the liver.
So the best actionable advice I can come up with is probably: "Eat more collagen"
From the looks of it, the increased consumption of glycine supplements won't affect oxalate. Yes, glycine/oxalate ratio would be improved, but this would not decrease the amounts of oxalate. So the associated problems related to the excess of oxalate would persist.
I'd be interesting to learn how fasting affects the expression of said gene. Thats the easiest intervention anyone can take. (FWIW, I've been treated with a 12 day supervised waterfasting therapy for NAFLD and it reduced the volume of my liver by nearly 20%).