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How is it possible that the Red Bull Zero contains 0 gramms of fat, carbs and protein, but it still has 1.8 kcal of "energy". I always thought that the human body can gain energy only from 3 kinds of nutrients: fat, carbs and protein. Is there a 4th kind? Or they just display an energy value that's not accessible to the body?

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WYSIWYG
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Crouching Kitten
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    This is slightly off-topic, since it's very unlikely to be related to your question - but yes, humans can gain energy from many more things than just sugar, fat and protein; it's just that those three are dominant in the food we eat. One example would be alcohol (ethanol); we can also process polyols and organic acids. Even fiber, which is often considered empty (and useful, mind) filler can be partially digested for about 2 kcal/g - so a single gram of fiber would be enough for that energy value (while being both a carbohydrate and a (poly)sacharide, it's usually listed separately). – Luaan Jul 18 '19 at 08:13
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    @Luaan Exactly, I wanted to mention ethanol too. It was a big surprise to me and I actually had asked a question to find out how is it possible. – Tomáš Zato Jul 18 '19 at 15:19
  • @Luaan I thought that alcohol is a carbohydrate. – Crouching Kitten Jul 19 '19 at 09:00
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    @CrouchingKitten Nope. It does have carbon, oxygen and hydrogen atoms in the molecule, but that doesn't mean it's a carbohydrate, just like fats aren't. Especially in food context, "carbohydrate" essentially means "sugar", usually including some non-sweet saccharides like cellulose (in your photo, that would be in "Kohlenhydrate" but not under "davon Zucker"). Really, alcohol is closer to fats than carbohydrates, but even that isn't really all that useful. It's not commonly included in either group. – Luaan Jul 19 '19 at 12:17
  • @Luaan Thanks. So this means that the body can't convert it to glucose? So the only way the brain can make use of alcohol is if it's first converted to fat, and then to ketons? – Crouching Kitten Jul 19 '19 at 13:02
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    @CrouchingKitten The body does convert it to fats (if you're well fed), but I don't think there's any specifics dealing with the brain - after all, ethanol goes through the blood-brain barrier with no trouble. It has long been thought that ethanol doesn't cause the well known CNS symptoms on its own - it's the intermediate products of ethanol metabolism that do, probably mostly acetaldehyde. Assuming this is true, ethanol must be metabolised in the brain (and thus provide energy, as outlined in Tomáš's link), since acetaldehyde doesn't cross the blood-brain barrier. – Luaan Jul 19 '19 at 13:15
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    @CrouchingKitten I doubt anyone would recommend it as a food source for the brain, unlike sugars and ketons, though; for obvious reasons :) – Luaan Jul 19 '19 at 13:16

1 Answers1

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The list of ingredients on the can mentions "Zuckerkulör," which is caramel colour, which can have 2 kcal/g, according to one producer.

Next, there is "Citronensäure," which is citric acid, which can, as other organic acids, have 2-3 kcal/g, according to this source.

There is also taurine, which is an amino acid-like compound, so it could, like proteins, have 4 kcal/g, but is, according to Taurine Metabolism in Man (Journal of Nutrition), poorly metabolized and probably has less than 0.2 kcal/g.

It is sometimes allowed, at least by U.S. Food and Drug Administration, to round the amounts of macronutrients (carbs, proteins, fats) smaller than 0.5 g per serving to zero, which is what they obviously did in this case, but they decided to keep the summary of calorie values of all ingredients exact.

It is usually said that only 3 types of nutrients contain energy: carbohydrates, proteins and fats.

Digestible carbohydrates (sugars and starch) provide 4 kcal/g. Undigestible, but fermentable, carbohydrates, such as soluble dietary fiber, sugar alcohols or polyols (maltitol, mannitol, sorbitol, xylitol, isomalt) and organic acids (citric, acetic acid, etc.), can provide 2 kcal/g of energy in average. On the other hand, some carbohydrates (such as "Sucralose" from the ingredient list) are neither digestible nor fermentable, so they do not provide any calories.

The "fourth" nutrient that can provide energy (7 kcal/g) is alcohol (ethanol), but is not considered a nutrient by some authors.

According to Food Label Accuracy of Common Snack Foods article (Obesity, 2014), the calories on the food labels should represent usable calories (metabolizable energy):

Of note, it is important to distinguish that food label calories actually represent metabolizable energy, which is total caloric content minus calories that are presumably not absorbed by the body and excreted as waste.

Jan
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    This article says that ~95% of ingested taurine is excreted. KEGG also says that taurine is not converted into any energy molecule in humans. – WYSIWYG Jul 17 '19 at 17:54
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    Could it be Zuckerkulör (caramel colour)? It's just caramelized sugar. – AkselA Jul 17 '19 at 19:59
  • @AkselA -- answer should be edited to include your comment as that is almost certainly the answer. If not then it is that plus some of the other ingredients -- Aromen e.g. or anything else that constitutes a fraction of a caloric intake as, total, they only need to add up to <2 Calories. – user23715 Jul 17 '19 at 20:18
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    This reminds me of a "zero calorie" recipe I once saw which involved ten squirts of cooking oil. Somebody had calculated the calorie count of one squirt, rounded to zero, and then multiplied that by ten... – GB supports the mod strike Jul 17 '19 at 20:27
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    @AkselA There's very little caramel colour and, also, I'm not sure it has much energy in it: it's essentially already been partially burnt. – David Richerby Jul 17 '19 at 20:50
  • @DavidRicherby: I don't think there's much energy in a couple of drops of caramel colour either, but then again we are only looking for a very small amount of energy. – AkselA Jul 17 '19 at 20:55
  • @AkselA Oh, good point. I'd not noticed the actual numbers. Since the question is, essentially, "How is there more energy than I expected?", I didn't stop to think that "more than I expected" could still be "almost none." – David Richerby Jul 17 '19 at 21:16
  • @GeoffreyBrent Reminds me of how TicTacs have 0g of sugar per serving (1 mint), while they're probably mostly made of sugar. – JoL Jul 17 '19 at 23:14
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    @WYSIWYG, I checked that article and it really seems it is not taurine that provides calories. – Jan Jul 18 '19 at 11:19
  • @AkselA, it's quite likely that it is caramel colour and citric acid that provide calories. – Jan Jul 18 '19 at 11:45
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    @DavidRicherby: Why do you think all the sugar in the caramel is burnt? Ingredient design is an art nowadays. Listing sugar as an ingredient is actively avoided nowadays. Burning just 1% of the sugar and labeling the whole as "caramel colour" would be a sneaky way to put sugar in the recipe without explicitly listing it as such. And it's certainly a whole lot cheaper than putting in honey (another common "non-sugar" ingredient) – MSalters Jul 18 '19 at 14:11
  • @MSalters 1kcal of sugar is a tiny tiny amount and not really detectable as sweet in a volume like this, so what you describe probably doesn't apply here. – Bryan Krause Jul 19 '19 at 17:39