This question dug itself into my brain and it won’t leave. So here goes: Is it possible for a human to survive solely on vitamin supplements and water? People eat because they need nutrients, but what if you take pills that provide those nutrients? Apologies if this is a little vague or too broad.
Not vitamin supplements. There’s no protein, carbs or fat in a vitamin tablet and all are essential.
Widen the criteria out to all diet supplements though and I can’t see why you couldn’t survive, you’d be basically taking all your food as powdered shakes.
Supplements generally have negligible caloric content. So, you might be getting your vitamins and minerals, but you’re still fasting. So, the answer would probably be, “for about as long as you could survive without eating food.”
You could go quite a while on just vitamin/mineral supplements, especially if you’re very heavy. But I would add some protein and fat to that. Carbs are unnecessary for survival (though you’d get a few if you ate enough meat or dairy.)
Sure why couldn’t you. Dietary supplements are used frequently to keep coma patients alive for extended periods of time. It’s not like nurses are cutting up pieces of meat and vegetables and forcing them down the patients mouths.
There’s a saying “If the gut works, use it” and people in comas whose digestive systems are functional are usually tube-fed, either through an NG or a gastrostomy tube. Unless they are on a special diet for other reasons, they often hook up a container of Ensure, Boost, Jevity, etc. although I’ve definitely heard of friends and/or family members making smoothies for their loved ones.
Some people in higher-functioning persistent vegetative states can eat “real” food if it’s fed to them.
And if the gut doesn’t work, they put a line in your vein and feed you fats, protein, and carbohydrates through that. It’s called TPN, or total parenteral nutrition.
Soylent has been available for a couple years now. It’s a powder you mix in water and is supposed to fulfill all your nutritional needs, although it doesn’t appear any controlled studies have been completed. It’s more than just vitamins (as noted above), but I suppose you could classify all the ingredients as supplements.
Sure, except the OP specified “vitamin supplements”. If your “supplements” included macronutrients (fats, protein, carbohydrate), then yes you could survive on them. If you’re talking vitamin pills and herbal bullshit then no, you couldn’t.
no. vitamins and minerals are micronutrients; things we need in milligrams or micrograms. They provide no macronutrients like protein, fat, or carbohydrates from which our bodies get energy.
Something my wife and I are all too familiar with.
It kept her alive for 6 months in 2011 and for 6 months in 2013. An amazing product that I never imagined existed. She carried around a blue backpack that had a fancy pump that delivered this stinky white milky stuff in a line that went from her arm to just above her heart.
Happily her digestive system is back to normal these days.
Yay! Yes, TPN is a literal lifesaver, and quite miraculous…but it’s still not ideal, by any means. It will keep people alive, but as soon as the GI system is up to the task, food is a much better option. 
Yes, long term TPN has side effects, and is hard on the liver long term. Always better to use an actual digestive tract whenever possible.
Vitamins and minerals, too.
That chromium and selenium were essential minerals was discovered after long-term TPN became feasible.
ETA: Minor7, you’re right - IV lipids really stink. Procalamine (IV protein) doesn’t smell very good either.
The only time I’ve personally seen ultra-long-term TPN was for hyperemesis gravidarum that didn’t respond to any known treatment. 
Not correct, your body requires Carbohydrates to function properly.
Without carbs your body suffers from:
-Irritability
-Nausea
-Bad breath
-Loss of muscle mass
-Muscle cramps
-Excessive fatigue and exhaustion
-Poor brain functioning
-Increase in fat percentage of the body
-Loss of sodium in the body
-Diarrhea or constipation
-Frequent headaches
-Loss of water content in the body
However, this does not mean, that you have to eat carbs in huge quantities, but you do need them.
we can use ketones for energy as well, but once your fat stores are gone, you’re in trouble.
Gee, tell that to the Eskimo peoples my Dad lived with. Or to me on my diet.
No, your body can happily convert fats and proteins to needed blood sugars.
*To the surprise of many (including Stefansson himself), he suffered no health problems during his decade of pure carnivorism. When he told people of his amazing experiences, he was met with skepticism from medical authorities who asked him to undertake a study that would replicate the results. He and a fellow explorer named Andersen agreed to eat an all-meat diet for an entire year in a closely observed setting…Examinations at the end of the observation showed that both men were healthy while on the diet. The authors write:
There were no subjective or objective evidences of any loss of physical or mental vigor. The teeth showed no deterioration and gingivitis had disappeared. There was, however, an increase in the deposit of tartar on the teeth of [Stefansson]. Bowel elimination was undisturbed.
Though neither man was overweight to begin with, and weight loss was not the goal of the experiment, both men lost a few pounds during the year. This was despite the fact that calorie intakes ranged from 2,000 to 3,100 kcal. *
Back to the OP: I have a large Vitamin catalog in from of me. It includes protein and fat supplements, as well as “green foods”. Thus, counting these as ‘supplements’, then yeah, sure.
Do you need some kind of bulk to keep the nutrients from just sliding through without being absorbed?
You can probably live off of vitamin and mineral supplements, protein powder, vegetable oil, sugar and water. I have no idea how unhealthy it would be though.
When I worked at the hospital, we would sometimes have morbidly obese people on TPNs, and the technicians wondered why. I replied, “Obese people need to eat, too - just not as much.”
The biggest diet I ever personally saw ordered was 4,000 calories a day. The patient weighed over 500 pounds, and the doctor wanted them to lose weight, but not too rapidly. Since it takes about 10 calories per pound per day just to maintain bodily functions, this would result in a weight loss of several pounds a week even without exercise.