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I am trying to determine the bare minimum nutritional requirements to survive as a human, ignoring energy (caloric) requirements. Another way to ask this question is: What elements can humans not live without? I am not inquiring solely about what nutrients are needed, but also their approximate amounts.

Imagine pills that a person can take that covers all their base nutritional needs and that after taking this pill the person can eat whatever they want to meet their caloric requirements. Hypothetically, this pill could have some amount (how much?) fat, carbohydrates, protein, fiber, minerals, and vitamins, and the person could subsequently eat any other food to meet their caloric requirements knowing their nutritional needs would already be otherwise met. Lets ignore the possibility of the person suffering from health issues due to eating too much of any specific food to meet their caloric requirements (e.g., taking the magic pills and then eating only butter).

A person in this situation could think "Ok I've got most of my bases covered, now I just need to ingest another 1000 calories of (almost) anything I want).

What nutrients are absolutely necessary for humans to survive indefinitely, and how much of these nutrients are required?

I am hoping for a complete list with approximate amounts (e.g., 20g fat, 20g carbohydrates, 1mg Vitamin X, .05mg Vitamin Y, 10mg mineral X).

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  • $\begingroup$ This is not very answerable because each person is different, significantly enough that most recommendations are on the safe side of (mal)nutrition. Every human being requires essential micronutrients and macronutrients which are well known and established by now, but the amounts depend extremely on what you consider doing with the body. The bare minimum calorie intake will not allow you to thermoregulate in the cold or move. Similarly, people have quite varied uptake of nutrients; e.g. people with malabsorption of iron can have anemia, and their minimum iron intake may be relatively higher. $\endgroup$
    – S Pr
    May 20, 2019 at 14:16
  • $\begingroup$ My whole point is to ignore calories and to focus on the rest. Are you telling me that a hard working farmer needs orders of magnitude more of minerals and vitamins than an average person? Calories yes, but the rest? $\endgroup$
    – Behacad
    May 20, 2019 at 17:02
  • $\begingroup$ I’ll also add that approximations and ranges are acceptable answers. The fact that the answers are hard to pin down does not make it unanswerable. $\endgroup$
    – Behacad
    May 20, 2019 at 17:10
  • $\begingroup$ These sorts of "numbers demands" questions are not typically well-received here: that's not how biology (or medicine) works. The way you are responding to comments giving you good information with demands for what is an 'acceptable' answer is (probably unintentionally) rude. I'd normally recommend closing this question as too broad, but I think you've gotten a good frame-challenge answer that rescues the question a bit. $\endgroup$
    – Bryan Krause ♦
    May 20, 2019 at 21:24
  • $\begingroup$ I get what you're saying, but of course this is how medicine and biology work. There is a number that makes approximate sense for how many of each nutrients the average human needs. It varies yes, but we know 1mg of Vitamin C isn't enough in a day, and 5000 is too much. Nutritional labels are universal and focus on this question, so certainly there is a rough answer. Maybe the answer simply involves tabulating all of recommendations and perhaps justifications for some of them. $\endgroup$
    – Behacad
    May 20, 2019 at 21:35

3 Answers 3

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Essential nutrients include (NutrientsReview):

  • Water
  • 9 amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, threonine, valine
  • 2 fatty acids (alpha linolenic and linoleic acid)
  • Vitamins: A, B1, B2, B3, B5, B6, folic acid, biotin, B12, C, D, E and K (and choline, which is considered a vitamin-like substance)
  • Minerals: calcium, chromium, chloride, copper, iodine, iron, manganese, molybdenum, phosphorus, potassium, selenium, sodium, zinc

The "bare minimum" intakes of most nutrients needed for survival are not known, because they could be determined only by studies in which participants would be given various low amounts of nutrients and observed for how long they can survive. The following are estimations of the lowest intakes of some nutrients needed to remain healthy.. Note, that this are not "recommended" or "optimal" intakes.

Protein = 35 grams per day (Metabolic Basis of Obesity)

Fat = 20% of total calorie intake, that is 44 g per day in a 2,000 Calorie diet (PubMed, 2017)

Carbohydrates = zero (National Academic Press)

Only 2 fatty acids and 9 amino acids are essential, so theoretically, you could consume only those and would be fine. In foods, these acids usually do not appear individually but as part of fats and proteins, so the recommendation is given for fats and proteins - if you meet that, you will likely consume enough of the essential acids. Theoretically, you can survive without consuming any carbohydrates, because all of them you need can be synthesized in your body. People have survived and remained healthy without consuming carbohydrates for a year or more (National Academic Press).

Sodium = 200 mg per day (Recommended Dietary Allowances: 10th Edition)

Water = 1 liter per day (only in ideal circumstances with minimal sweating; in the table, water requirement = "net water loss") (National Academic Press)

Here's a table with dietary reference intakes for vitamins, minerals, carbohydrates, fats (and separately for the 2 essential fatty acids), proteins and water (Nationalacademics.org), which should be sufficient for most individuals in a given sex/age group to remain healthy long-term. These amounts can be considerably greater than what is needed just for survival.

In Recommended Dietary Allowances: 10th Edition, in the Table 6-1, there are "estimates of amino acid requirements" for all 9 essential amino acids.

There was a man who was fasting for more than a year, drinking only water and getting potassium supplements, and the concentrations of most nutrients in his blood remained normal and he had no health issues (Postgraduate Medical Journal, 1973). This shows how difficult is to find "bare minimal" amounts of nutrients.

Yes, it is possible to make a "pill" with only essential nutrients in required amounts included. Such products already exist, but I don't want to promote them, because there is no evidence of their long-term health benefits and safety.

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  • $\begingroup$ Thank you for this helpful answer. I'm a bit confused about the fat comment, since the "essential nutrients" list you shared actually does not include fat beyond the two essential fatty acids recommended. The man who fasted for a year is a wonderful example that gets to the point of my question. This guy seemed to be straggling the line of the bare minimum! $\endgroup$
    – Behacad
    May 21, 2019 at 16:00
  • $\begingroup$ Can you elaborate on how fats proteins and carbohydrates are not essential? Are you suggesting that a person could live a long healthy life without consuming any fat beyond a reasonable amount of those two fatty acids? Most importantly to my question is how many grams of fat and protein are needed to reach the recommended amount of fatty and amino acids? Assuming you could consume those nutrients in pure form. $\endgroup$
    – Behacad
    May 21, 2019 at 19:26
  • $\begingroup$ Yes, theoretically it is enough if you consume only essential fatty and amino acids. Check my updated answer. $\endgroup$
    – Jan
    May 22, 2019 at 8:13
  • $\begingroup$ thank you. For curiosity's sake I tabulated the total mass required to address the essential nutrients you mentioned based on FDA guidelines and such. It seems to add up to about 20g for an average young man, and taking into account the fat and amino acids (ignoring protein because that is taken into account with the amino acids?) it seems like the energy value for these nutrients is only about 75 calories. Does this mean the average young man can have his nutritional needs met by ingesting 20 grams and 75 calories (ignoring energy requirements) +water? $\endgroup$
    – Behacad
    May 22, 2019 at 16:39
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    $\begingroup$ 'it seems like the energy value for these nutrients is only about 75 calories' @Behacad these nutritional requirements have nothing to do with energy content. These are substances your body requires to sustain life regardless of your caloric intake. Think of it this way: your car may have a full tank of gas, but if your engine doesn't have any oil, you engine will seize up in a matter of minutes. The engine doesn't get energy from the oil, but it need's it to function. Similarly, you may be getting plenty of calories, but if you don't have the right nutrients you'll die of malnutrition. $\endgroup$
    – Charles E. Grant
    May 22, 2019 at 17:07
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You are not going to get an exact number because of variation in body mass, age, sex, and metabolism. life style also has a huge effect,what someone doing hard labor needs is vastly different that what a comatose person needs. Minimums are harder because of the ethical problems with studying the bare minimum humans can survive on long term.

The best you will get is averages for a healthy intake of different age/sex brackets. which can be found here. These reflect the minimum below which it starts having a noticeable negative impact on health.

Essential Macronutrients are materials you need in bulk and generally fall in to the categories of water, amino acids, nucleic acids, carbohydrates, and lipids. Some of these are also major caloric sources, but there still is a daily requirement even if another source is supplying calories.

Essential Micronutrients are materials you need trace amounts of, basically essential vitamins and minerals.

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  • $\begingroup$ I don't need an exact number, but approximate numbers are good enough. Certainly these don't vary by such a great deal. I doubt a very large man needs 10x more Vitamin C and an average woman. If I am wrong here, let me know, but still approximate values are good enough. Second, you mention doing labor and metabolisms, but these require calories, not nutrients, which is what my question is getting at. I'm not interested in calories, I'm interested in the rest! A hardworking farmer needs many more calories yes, but does not need much more iron. $\endgroup$
    – Behacad
    May 20, 2019 at 14:38
  • $\begingroup$ Behacad, the requirements for non-caloric nutrients (micronutrients = minerals and vitamins) actually do increase with calories someone spends, as John said. Someone who burns a lot of calories and then consumes 2,000 Calories worth of carbohydrates, will likely need twice as much vitamin B1 than someone who consumes 1,000 Calories of carbohydrates, because vitamin B1 is involved in carbohydrate metabolism. $\endgroup$
    – Jan
    May 20, 2019 at 17:47
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The US FDA has published many of these, conveniently summarized here: Reference Daily Intake, but the original sources are here. I know that the link only answers are discouraged, but there is really too much information to be summarized here.

This information may be somewhat misleading, since the form of food is important too. Famously a certain amount of inert dietary fiber needs to be consumed to keep the digestive tract healthy.

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  • $\begingroup$ Do these values represent a suggested amount (e.g., if you need 2000 calories, then you can eat X grams of fat), or biological requirements? For example, would some people get in trouble for eating less than 65g of fat? $\endgroup$
    – Behacad
    May 21, 2019 at 0:46
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    $\begingroup$ @Behacad, not to be cranky, but I'm not going to read the articles for you. I'd suggest you read the original papers from the National Academy fo Sciences, Medicine that I link to. They go into great detail defining what it means to be "required". $\endgroup$
    – Charles E. Grant
    May 21, 2019 at 0:51
  • $\begingroup$ No worries, I get you. Just thought I would ask in case you happened to know! $\endgroup$
    – Behacad
    May 21, 2019 at 0:55

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