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Comment by pattusk | Hacker News Reader

I remember many years ago when I first moved to Asia, people looked at me wide-eyed whenever I took medicine with orange juice or a can of soda.

I dismissed it as some urban legend on the level of the fan-death [1] until a doctor explained to me the adverse interactions of citrus fruits on all sorts of medicine.

I have been taking my medicine diligently with water ever since, but it still amazes me how incredibly different the distribution of such common and potentially life-saving medical knowledge can be across countries and cultures.

[1] https://en.wikipedia.org/wiki/Fan_death

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Being a little pedantic, the drug interactions part of the article applies to bitter citrus specifically: not just grapefruit (despite the title!), but not all citrus either. Typically “orange” is used to refer to sweet oranges, not sour oranges.

As to soda, I struggle to imagine a soda that has any amount of juice worth taking into account…

Fresca is right on the line, with a can shown to increase serum concentrations of some drugs by 50%--- not enough to matter in most cases.

> As to soda, I struggle to imagine a soda that has any amount of juice worth taking into account…

It's not just the juice. The acidity level of your stomach affects absorption of many drugs - some are absorbed faster in an acidic environment and some are absorbed slower, which means drinking even Coca Cola (pH: 2.5) with your medication could potentially have the effect of negating your medication or increasing the effective dosage substantially, depending on the drug.

Your stomach is already much more acidic than Coca Cola

Indeed. It’s typically a pH of 1.

And your body is really good at buffering acids and bases. Once your stomach empties into your small intestine, bicarbonate is released which raises the pH to around 5.5 I believe which is necessary for digestive enzymes to work.

Think you'd be surprised. Coke pH is 2.5, and it seems that ideal human stomach pH is 1.5 to 2.5. Fun fact: you can use Coke to clean your toilets.

Orangina?

Sodas often contain significant amounts of ciric or phosphoric acid.

Per the article, the drug-interaction problem comes from furanocoumarins depleting your cytochrome P450. There's nothing in there to suggest that refined acid (as opposed to unprocessed juice) would include furanocoumarins.

Indeed, "citric" acid produced today comes from mold cultures that A) don't produce significant quantities of FCs, and B) even remove FCs from their environment by adsorption.

Sure of course, I was just replying to the question about fruit juice and sodas.

I once read that CocaCola is the largest consumer of lemon oil in the world. So I am sure their syrup has plenty of it.

I don't think this logic tracks - there are so many Cokes produced annually that even if every can had only 0.1 mL of lemon oil they'd still probably be the largest consumer.

Not too mention that the Coca-Cola company also own a staggering amount of more or less known brands, the bigger of which of course being Sprite and Fanta, which are likely large consumers of lemon oil.

I'm curious what you ever made, if anything, of the looks you would get for drinking ice water. I know it is considered very unhealthy with a strong taboo there (at least, my data is from China, not sure if applies to other asian countries). I once asked a Chinese friend would they rather their hypothetical child habitually drink ice water or smoke cigarettes, and she knows the health risks of cigarettes, and she was genuinely on the fence and torn.

In China there was a longstanding practice of using nightsoil (i.e. human feces) as fertilizer. The health risks are great and doing it safely requires strictest adherence to hygiene protocols. Everything is boiled for safety, even lettuce is wilted in the pan. It's no surprise that ice water gets you the crazy look.

Food taboos oftentimes make sense. Sometime ago someone mentioned traditional, cyanogen-rich varieties of cassava, which are pest-resistant but require boiling for hours in an open pot. If you omit that you end up with motor neuron disease, konzo as they call it, but only after several years. So it's not surprising that superstitions sprang up around the plant, some of which are actually protective.

I remember somebody mentioned if they drink ice water after exercising and getting really hot, it can cause them to pass out.

Anybody have the details on that effect?

It's true and it happens when nerves around the stomach (called vagus nerve) react to the cold by sending a signal to the brain. Because among other effects signals from the vagus nerve reduce cardiac frequency, you can indeed pass out as a result.

Not a doctor, but it happened to my wife and it was a little scary.

What is the feared effect?

Water-borne diseases, I'm sure. It's easy for ice to be contaminated; if you go to a part of the world where tap water can't be relied on to be safe, skip the ice.

No, that’s not what he’s referencing. There’s a Chinese belief that cold water makes you sick. Even sanitized, filtered water and ice made from the same. The fear is over the temperature, and is akin to Korea’s fear of electric fans in its irrationality.

I understand, but my guess is that the origin of this belief was from times when cold water would make you sick because it was likely to be contaminated. Given that, it's not irrational at all. If you believe something that increases your survival but you believe it for the wrong reason, it still increases your survival.

That might be the origin of the belief, but it’s not what people are fearing today.

>Korea’s fear of electric fans

Say what? Do tell.

Oh my. You’re one of today’s lucky 10,000:

https://www.theatlantic.com/health/archive/2017/05/is-this-g...

I knew a girl from Hong Kong who carried the same belief so it's not just SK.

It's interesting the article didn't mentioned suicide, which I've seen mentioned before as a cause of the myth. The story goes that papers popularised the concept as a way to avoid specifically naming suicide as a cause of death, as a kind of shared understanding while preserving the honour of the families. But a lot of people took it seriously so the idea gained traction.

I consider most, if not all, tap water unsafe and recommend further filtration practices like reverse osmosis.

Secondly, I’ve seen many ice machines throughout my prior work and would strongly recommend avoiding ice cubes as most kitchens don’t clean these properly.

Cultural habits don't necessarily need a well defined cause and effect. The effect in such cases is that people think you are strange for not playing along.

The root of the habit in this case is Chinese medicinal beliefs. Here is a bit of a summary.

https://www.cheng-tsui.com/blog/hot-water-in-chinese-culture

"In traditional Chinese medicine (中医, zhōng yī), hot water is used to expel excess cold and humidity from the body, and it is believed to promote blood circulation. This helps detoxify the body and relax the muscles. Cold water supposedly has the opposite effect, slowing organ function and causing painful muscle contractions. Thus, hot water is often touted as the cure for everything from sore throats to stiffness to cramps to fatigue."

Of course, modern people also know that untreated water is not safe. That doesn't explain an aversion to cold bottled water or other drinks though, which while far from absolute is more common than it is in Western countries.

Across cultures and countries is not even the least of concerns, simply across doctors and other medical professionals, the communication to patients is not consistent. How this is solved is probably at the facility level and probably something that needs to be in the packet given to patients along with all those wonderful privacy and health notices.

This based on my mom doing chemo which came with other types of drugs to counter issues arising from that treatment and surgery. Suffice to say some doctors warn about the issue with grapefruit while others even dismissed the concerns. However this goes back to her quip about diabetes, you can get four opinions by asking three doctors.

My mother is doing chemo, and they definitely warned against grapefruit and the kind of oranges used in marmalade (not orange juice).

I'm wondering if this could be related to how common Pomelo (柚子) is in China (and maybe some other Asian countries, not sure), which per the article has the same effect and is also consumed in sizeable quantities.

Ooh, that's good intuition. Citrus genetics is complicated, but pomelo is the ancestor of grapefruit. (Bergamot and bitter orange are also closely related.)

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