Do we really need to take electrolytes when we fast?

I've been doing IF and 24/48 hour fasts for some time now, but recently have become interested in doing an extended fast of 7-14 days, and perhaps beyond that, mainly for the autophagy and mental benefits. About me: 29M, 6'3, 200lb. Not in bad shape, but I don't really exercise outside of walking. No medications, no major health problems, and normal recent metabolic labs (fasting insulin 7.7, would like to get that lower). My main question about doing an extended fast pertains to electrolyte and vitamin supplementation. I've been reading the fasting book by Jason Fung, and he says that electrolyte supplementation is not needed in extended fasts, because the body has ways of regulating its electrolyte levels without external supplementation. But here I see a lot of people adding snake juice (or similar) salts to their extended fasts. Why add the salts if they're not strictly necessary, or am I missing something? Could I just do a water-only fast with high-quality bottled spring water (such as Mountain Valley) and be fine? Finally, many recommend taking a multivitamin during an extended fast. Is this really necessary? Our ancestors would not have had access to synthetic vitamin pills during extended fasts in the past, and the fat soluble vitamins wouldn't even get absorbed since I wouldn't be taking in any food, and therefore no fat. thanks in advance for your wisdom!

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My personal experience is electrolytes were essential. My first extended fast I couldn’t stay hydrated no matter how much water I consumed. Until I started supplementing with sodium and magnesium, etc., it was quite uncomfortable. I had a dental appt as well during that time and no matter how much water they gave me, I was dry and parched almost instantly. If you don’t have sodium there’s nothing to hold the water. So, my experience is not in-line with Dr. Fung’s explanation.

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For me, adding electrolytes has been the most important thing in being able to finally do a extended fast (8 days). Without them, I was struggling to get past a full day because the hunger cravings were too much. With them, you literally do not get hungry, you just miss the taste and feeling of food.

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I generally don’t take electrolytes during multiday fasts. I find my success comes down to willpower/motivation more than anything else.

I only recently bought some fasting supplements (in capsule form). I took one on day two of what should have been a 7 day fast. The diarrhea I experienced was horrible, lasted for the whole of day three and four and stopped when I stopped the fast. I’m not 100% sure these are related but I suspect so as I’ve never had these symptoms before.

The longest I did was a 14 day fast, during this time I would let a sea salt crystal melt on my tongue every now and again. That’s it.

Regarding the multivitamins, I do take them.

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Electrolytes might not be required to complete an extended fast for most people, but they’re zero calorie, don’t break the fast, and sure as hell make it easier lol.

Without electrolytes, around day 3 I get confusion, headaches, and lethargy leading to a lot of small naps. Granted, this doesn’t make it any easier to get actual rest at night, though. That becomes elusive when I fast.

I just don’t see any reason to make fasting any harder than it needs to be. If there are cheat codes that get you the same results, why not lean on science to make this task more bearable?

I also take melatonin to go to sleep easier, because while fasting I can’t fall asleep to save my life. Is it required for the fast? No, but it makes it easier and I’m still dropping weight like crazy.

Though in regards to multivitamins, I agree with you. No point to waste fat-soluble substances when there’s no fat in your stomach.

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It’s definitely nessecary when you’re still practicing multi-day fasts. After enough fasts I could go 5 daya without feeling any symptoms related to electrolyte deficiency. I do of course if I’m not feeling well. BTW I barely take more than 500 steps a day so that probably helps.

To each to their own