What Breaks a Fast: Supplement Edition

Last week, I explored the impact of all the various foods, beverages, and food-like substances people consume while fasting—and hoping to maintain a functionally fasted state in the post, “The Definitive Guide To What Breaks a Fast.” Does MCT oil break the fast? What about coffee, tea, or bone broth?

There were more than a dozen, and I even did a follow-up. Today I’m going to discuss whether commonly-consumed supplements break the fast.

Let’s go:

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Fish Oil

Fish oil is pure fat. If you’re taking the average supplemental dose of 1-2 grams of fish oil, it’s not a problem. That’s not even a teaspoon. It’s about 9-18 calories.

You may burn slightly less fat than you would otherwise, but in the grand scheme of things, a few grams of fish oil won’t break the fast.

Cod Liver Oil

Cod liver oil is fish oil with extra vitamin D and vitamin A. As long as you keep the doses low enough, cod liver oil won’t break the fast.


Multivitamins do not break a fast. They are usually non-caloric. However, not all of their components will be absorbed very well on an empty stomach, so keep that in mind.

If you’re still not on board, note that in the older studies with really overweight people who fasted for upwards of a year straight, they usually supplemented with a multivitamin.

Food-Based Multivitamin

A popular one I’ve seen around—Alive, made from kale and raspberries—has just 2 grams of carbs per dosing. It’s not ideal, but it’s not a deal breaker—or a fast-breaker.

Gummy Vitamins

Gummy vitamins have the potential to be about 5-6 grams of sugar, a gram of protein (from gelatin), and a gram of fat (if including omega-3s) per serving, so they’d arguably break the fast. Plus, they taste like candy and are likely to stimulate cravings and make fasting harder.

Gummy vitamins break the fast.


Potassium is non-caloric and does not break the fast. In fact, it can help you handle the fast better by replenishing electrolytes.

Potassium doesn’t break the fast.


Creatine contains no calories and has no effect on insulin secretion (or glucose in the absence of calories).

Creatine does not break the fast.

Protein Powder

Protein powder provokes an insulin response, which opposes autophagy, which means you’re breaking your fast. Plus, protein powder contains calories.

I’m going to say “yes, protein powder breaks the fast.

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If you’re strict and technical, then yes, collagen breaks a fast. There’s evidence that glycine—the most prominent amino acid in collagen—can inhibit autophagy, but it was a convoluted animal study where inhibiting autophagy with large doses of glycine after brain injury actually improved outcomes. It probably doesn’t apply to someone adding a scoop of collagen to their coffee. Besides, even if it slightly reduces autophagy, a little collagen won’t negatively impact ketosis, fat-burning, or energy intake.

I’m going to say “technically yes,” but “realistically no, collagen doesn’t break the fast.” Avoid if your main focus is autophagy, however.

Branch Chain Amino Acids (BCAAs)

BCAAs trigger an insulin response and thus stop autophagy…and the fast. That said, many proponents of fasted training recommend using BCAAs before a workout to help preserve muscle and improve the post-workout anabolic response.

I’m going to say “yes, BCAAs break the fast.”

Vitamin D

Vitamin D is fat soluble and thus comes packaged in an oil carrier, but the dosage is so small that it won’t affect your fast.

Unless you find that 1/8 teaspoon of olive oil ruins your fast, vitamin D won’t break a fast.


Probiotics contain no calories and will not break a fast. However, they are best absorbed in the presence of food—the food protects them as they travel through the digestive system, and most probiotics occur naturally in food—so taking them during a fast is probably, mostly useless.

Probiotics don’t break a fast, but why take them during one?


Pure prebiotics will not break a fast, as they contain no digestible carbohydrates. Prebiotic-enriched foods will break a fast, as they do contain calories.


Adaptogens are compounds, usually herbs or herb derivatives, that modulate your stress response. They improve your ability to tolerate and respond to stressful situations; they don’t blindly inhibit the stress response if the stress response is warranted. They keep you honest and counter unnecessary stress responses. They contain no calories, unless you’re chowing down on a big hunk of maca or ashwagandha root. In fact, most adaptogens have traditionally been consumed in tea form, extracting the active compounds and leaving behind any calories. Have at ’em.

Adaptogens do not break the fast.

Mushroom Extracts

Medicinal mushroom extracts come from mushrooms, which are technically food. But the amounts you take are so low—usually no more than a teaspoon—that they won’t impact your fast or provide any significant amount of caloric energy. Four Sigmatic has those “mushroom coffee” blends you add to hot water. They can get up to about 30 calories per serving, but even that’s going to let you maintain most of the fasting benefits.

Mushroom extracts don’t break the fast.


I used to keep the old Trader Joe’s melatonin on hand because it was half a milligram, whereas most other melatonin supplements are in the 3-5 mg range. It was also sweet, tasting like those white Valentine’s Day mint hearts you used to get back in the day. I haven’t come across any sweetened melatonin supplements since Trader Joe’s phased those out, but that’s the only thing I’d worry about on a fast.

Melatonin does not break a fast.

Final Note: Most supplements are okay to take on a fast, though the lack of food may make absorption more difficult. If you have any other questions about supplements on a fast, drop them down below. Thanks for reading, everybody.

TAGS:  calories

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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54 thoughts on “What Breaks a Fast: Supplement Edition”

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  1. I’m going to gather all of the things that Mark says don’t break a fast and take them all together on a morning in the middle of a fast.


  2. Mark, what about desiccated liver supplements? Too low dose to break a fast?

  3. I love this series on what breaks a fast. I’ve been fascinated by fasting for a long time, and my first fast was probably around 1991. Back then, it was water only, no lemon juice, it has sugar. Then several years ago it was a fashion to fast for 40 days among religious groups. I didn’t participate but I followed several youtube channels where people told about it. A woman said she was taking a multivitamin every day, and salt and she had a flare of hunger each time but she thought it was important. Then she ate basically a steak dinner, and she went right back on her fast for another 40 day fast. The people on “Curezone” freaked out on her for not eating just fruit to break her fast (which was the “correct” way). I’ve never fasted that long.

    But I did try the collagen coffee in the morning and it’s a huge improvement over my water only intermittent fasting. It kills hunger so well that even that night, I don’t have cravings. So far. It’s an advanced technique that I’ve adopted now. Thanks very much, and that goes to the blog readers too. Really great discussion, everyone, please keep it going.

  4. My simple heuristic for a fast is to avoid carbs and protein/ essential amino acids. That’s it really in a nutshell. Fat doesn’t appear to affect insulin response or autophagy (unless anyone has any references to say otherwise?) so I really don’t worry about consuming pure fat such as coconut oil, olive oil or butter and/ or low carb soluble fibre such as leafy greens, spinach, sauerkraut, mushrooms etc. Yes they might contain a few calories but I doubt that will have much of an impact over the course of an 18 hour fast. On the days I drink black coffee though, this suppresses appetite so much that nothing else is required during a fast. Not so easy on days without the caffeine though!

  5. If I do an extended Fast with only half my daily fats once every 2 days Lifting heavy every day and doing HIIT sprints I usually get good results, but most important I feel satiated and energetic all day.

    Just Salts and some lemon post workout

    what do you do that works like a charm?

  6. These lists are so helpful! Thank you! How about teas?Regular,. decaf and many herbals list ingredients but don’t have a nutritional breakdown. If sugar in some form isn’t listed, are teas ok during fasting?

    1. I would recommend against those entirely whether you’re fasting or not. If you’re into horror stories you should look up the side effects.

  7. Hi Mark,
    In last week’s post you mentioned Stevia, Erythritol and Xylitol etc not breaking a fast. I just read “The Stevia Deception” by Dr Bruce Fife and what an eye opener. Basically there have been animal studies where these have kicked people out of ketosis. I dumped all my supplements etc containing non sugar sweeteners and even switched to a different toothpaste to be safe.

  8. Something I have never really seen explained is just how much fat one needs to absorb fat soluble vitamins. Does anyone have a lead?

  9. It may sound silly to ask, but the Organifi Greens supplement, would that break a fast?

  10. Can I fast and still eat something? What about a cheeseburger and fries? Can I have just three bites of a waffle? Does extra water without lemon count? Ah, Snowflake “Fasting”…please continue this series!

    1. I was wondering if Glycine breaks a fast both in case you would be interested in autophagy (24+hours) and in case you would not (16-20 hours).

  11. What about oils like peppermint oil? Sometimes I like to flavour my water and coffee with one or two drops. Does this trigger an insulin response similar to artificial sweeteners and therefore break the fast if my main goal is autophagy?


  12. I found and was taking some fiber powder before, pretty sure it was psyllium. Metamucil or something. The bottle said it was tasteless but I actually found it kind of sweet.

  13. I am taking a Grass Fed organ complex in a dried powder form. Will this break a fast?

  14. 5-HTP: Wish 5-HTP had been covered, but understand everything can’t be highlighted. Anyone know if 5-HTP would break a fast?

  15. Hi Mark,

    Would pine pollen or seabuckthorn extracts/powders impact a fast? What about mushroom tincture? Guarana?



  16. Mark,

    Thanks for this mini-series! It is so helpful!

    I use IF most days of the week, not for autophagy. Just recently discovered that adding 3-4 tablespoons of my homemade kefir (made with unsweetened nut milk) to my morning coffee really makes it creamy and delicious, and gives me another vehicle to ingest it. Will that break my fast? I will say that I am still in ketosis, have excellent blood sugar control, and am still losing weight when eating OMAD. So… I guess I actually have my answer…Does that sound correct? ? Thank you very much!

  17. This is very helpful thank you! I am also supplementing iron – does it break a fast?


  18. hi Mark,
    I am attempting KETO diet with your 21 day Reset book, I am vegetarian, would love to hear thoughts on success stories if you have them, and more guidelines for us. I was Vegan, but need eggs or something. . . please advise.
    Protein powders with whey I did select, and some eggs, but mostly I eat Vegan if possible.

  19. Hi Mark, thank you for your article.

    You mention fish oil supplements have 9-18 kcal per serving, but that it doesn’t break the fasted state. I was under the impression that anything with calories does indeed break the fast since it signals your body to digest food and thus interrupts autphagy and other metabolic activities.
    Does it affect autophagy? If so, how?

    Thank you!

  20. Will a sugarfree 10 calorie keto supplement that includes potassium, sodium, and magnesium break a fast?

  21. I’ve been taking liquid melatonin “wow” brand 3 mg drops. Also the brand “KAL”. Thoughtskn these? Thanks

  22. Hello

    I have high blood pressure. I workout consistently and I am only 42. I would like to do intermittent fasting. I need some caffeine. Are there any options for me? Have you heard of alani Nu, it’s “natural preworkout.?” Do you know of any pre workouts that trigger insulin?

  23. I’m surprised you didn’t mention calcium; will it break a fast? My fish oil has 1 g of carb in it and 35 calories, is that still okay? Also, fiber capsules? They have 10 calories and 3 g of carbs in them per 6 pills which is a serving. I take 2 pills a day; will any of this break my fast?

  24. Will 6 grams of pure organic spirulina break a fast?

  25. Will an organic iron supplement made from vegetables break a fast?

  26. Please tell me that you can answer this question. Does desiccated beef liver capsules break a fast?

  27. Hey… Amazing article you have post Mr. logan too much information you have describe in this article about pine pollen… It really helpful information for everyone and i’ll keep in mind in future for good health. Thanks for sharing this article…..

  28. I disagree with your assertion that probiotics are best absorbed if taken with food. The opposite has actually proven to be true in several studies (and during a fast is an ideal time to take them). Stomach acids destroy probiotics. Eating creates an acid environment int the stomach and destroys probiotics before they are able to make their way to the lower intestine where they are able to colonize.

    1. Thank you, came here to say the same. Liquids take a very short time to leave the stomach when empty and go to the far less acidic gut

  29. There is a newer sugar substitute called “Sucress” which is pure stevia leaf extract and glycine, an amino acid. It comes in small packets, just like regular sugar and has zero calories or carbs per the label. Will it break a fast?

  30. I have a several questions for which its possible nobody knows the answer, so if you’re savvy, please answer me. I’ve recently begun fasting for heath reasons; and I realize these questions will likely be very unusual.

    I’ve heard that fasting is good to help break addictions, and I smoke cigarettes, even while I fast. The longest fast I’ve had so far was 3 days, and on the third day I didn’t feel like smoking as much as usual, but I still did smoke. Would it be safe to assume that if I fasted for a week +, I might lose my cravings for cigarettes entirely?

    Again on the addiction note, I’m addicted to kratom(it’s a plant that acts in opioid receptors, but supposedly isn’t an opioid, I’m not entirely sure), and take that multiple times a day, even while fasting, due to chronic pain. So far I haven’t noticed any difference in use as a result of fasting at all. Could it be expected that at a 30 day+ fast, I’d lose interest and be and to overcome the addiction and the reap the benefits of fasting I mention below?

    And finally, in addition to the kratom, I consume a fair amount of different adaptogens, even while fasting. I’ve always heard that if you fast for over 30 days, your digestive system shuts down, and after that your body becomes capable of miraculous healing, such as burning cancer for energy, healing cavities, etc.

    Will consuming adaptogens daily while fasting prevent one’s digestive system from shutting down, and in turn prevent the miraculous healing? I have a ruptured disk in my back, and I’ve heard that by fasting long enough, my body can correct itself.

    I realize my approach to health is somewhat dichotomous, and there’s a chance nobody knows for sure, unless they’ve done these same things, and seen for themselves. If anybody has any experience with this, I would very much appreciate your input.

  31. Hi, I take 25 mg of Benadryl & 250 mg of Magnesium right before bed, does this break my fast? If so, I may need to move the time I take them

  32. Hi does GABA, L-tyrosine, 5HTP, zinc break fasts?



  33. Thank you for this, Mark.

    I get hypoglycemia sometimes. Both fasted and reactive; but not too often.

    I was worried about the high B6 content in sugar free Monster drinks that really help me extend my fasts so I switched to “Nocco” ones which just contain 100% RDA. I do a 20-23 hour fast daily depending on how I feel.

    Unfortunately they contain BCAA’s and Sucralose. 3 weeks into using them I have been suffering from fasted and reactive hypoglycemia..and now I know why! A quick reddit search confirmed my hypotheses, but it’s reddit so… I searched on here. Thank you!

  34. what about glandulars? i assume they do, but the dose is very small, so I expect that it may not?? But I am not sure.

  35. What about animal supplements like beef organs from ancestral supplements?

  36. I on occasion take 10mg of Natrol melatonin (quick dissolve, strawberry) at night – while fasting, prior to bed – . I am fasting to reset and lose weight. Am I messing up my 15/9 IF ?

  37. I am wondering if the product: Primal Sleep will break my clean fast.
    The ingredients are: (in 2 capsules)
    Valerian Root 4:1. 160 mg
    L-Tryptophan 100 mg
    Gamma-Aminobutyeric. 100 mg
    Chamomile extract, 100 mg
    Lemon balm plant extract, 100 mg
    Hoops extract. 50 mg
    Lavender extract 50 mg
    Melatonin, 3 mg
    Magnesium Bisglycinate Chalate 100 mg