April 17 2019

What Breaks a Fast: Supplement Edition

By Mark Sisson

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:

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.


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.

On a related note, with supplements on my mind this week I thought it would be a good time to offer one of my favorite deals—just for the MDA community: 20% off my full supplement line, plus Primal Fuel and Collagen Fuel. It’s a great time to stock up on favorites or to try something new. Offer ends 4/24/19 midnight PDT. Use code WELLNESS20 at checkout. (Offer doesn’t apply for autoship orders.)

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28 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!