154656501 What Supplements Can I Take On A Fast? | Ingredientologist

What Supplements Can I Take On A Fast?

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Supplements during a fast

There are many opinions out there about what supplements are acceptable to take during a fast. Although many supplements are unlikely to ‘break your fast’, some are absorbed best by the body when taken with food so taking them may be a waste of your money, and some may actually disrupt your fasting progress. To avoid unintentionally breaking your fast with supplements, let’s get into understanding how fasting influences our bodies.

The health benefits of fasting are a result of your body being in a post-absorptive state, meaning your body can focus on maintenance and recovery instead of digesting and building. This shift from a fed to a fasted state is what I call the ‘metabolic switch’. Through fasting, your body undergoes many metabolic changes, which includes a fall in insulin levels and a rise in glucagon and growth hormone. These metabolic shifts allow fat to be broken down to produce ketones for energy, and for autophagy to occur, where your body rids itself of old and damaged cells.

When we eat, insulin is released from the pancreas and into the blood. Carbohydrates, followed by protein, cause the greatest rise in insulin, while fat causes little to no insulin response in the body. Unless fat is ingested in a significant amount of calories at a time, it generally has a very small effect on insulin levels. So, when considering what you can consume during a fast, look at the ingredients carefully. Does the product contain artificial sweeteners, sugars, fats or any fillers?

Ultimately, the most important thing to remember is to not have any sweetened and high caloric supplements. Look at the ingredients carefully and make sure they are low or no-calorie, and contain no sugar and zero artificial sweeteners. It comes down to personal preference, and I would suggest approaching your fast with an open mind. If it is going to make it easier for you, try certain supplements and then adjust or remove them for future fasts.

Taking supplements is completely optional, but some may help you push through the final few hours of the fast. Here are a few supplements to consider during fasting:

C8 MCT Oil

Why take it: Medium chain triglycerides (MCT) are commonly used on the keto diet mainly due to their rapid conversion into ketones by the liver, which can then readily be used as an energy substrate. The chain length determines the MCT properties and how rapidly they get metabolized. C8 MCT, which has 8 carbon atoms, is the most potent form of MCTs as it elicits more ketones, more rapidly compared to other C10 or C12 MCTs, giving you a greater energy kick. MCT supplements vary in their composition of C8, C10 and C12, with some products containing mostly C12 and some containing pure C8 or C10.

MCT can help with appetite suppression, increase energy levels and provide a cognitive boost. Taken in black coffee or tea they can help suppress hunger and give you an energy kick, although MCT does technically break a fast. They are fairly tasteless in either a powder or oil form, and can be mixed with tea or coffee or simply taken alone.

How much: Start with 1 tsp at first and increase up to 1 tbsp at a time. High doses can cause GI distress in some people. Too much will break your fast, but won’t prevent ketosis, so again, it depends on what your goals are.

Exogenous Ketones

Why take it: Exogenous ketones or beta-hydroxybutyrate (BHB) salts are essentially ketones supplied from an external source as opposed to being endogenous, or produced by the body. Most of these supplements on the market are ‘ketone salts’ in which the ketone, BHB, is bound directly to a salt such as magnesium, potassium or sodium. In some cases BHB can be bound to an amino acid. BHB salts directly increase plasma BHB levels, which is the major ketone produced by the body. The salts are generally palatable, easily mixed into liquid and have the added side benefit of providing extra electrolytes. During fasting they can help to significantly suppress hunger, are anti-catabolic and cross the blood-brain barrier where they can be used as an energy source for the brain.

Exogenous ketones can also help with adapting to a fat burning state by upregulating monocarboxylate transporters (MCT) in the cell membranes, which can be useful if you’re using fasting as a tool to increase your fat oxidation capacity. MCT’s transfer fats into the cell to be broken down into energy, and so having more of them increases the utilization of fat for fuel.

Beta-hydroxybutyrate exists in two forms which are mirror images of each other, termed ‘D-BHB’ and ‘L-BHB’. The ‘D’ form is the isomer that your body naturally produces and is 2-3x more potent than the ‘L’ isomer. Exogenous ketone supplements on the market often contain a mixture of the D and L forms of BHB, which may be less effective than D-BHB alone. Interestingly, our mitochondria have receptors that prefer the D-BHB, and the L-BHB can actually stimulate fat synthesis and could inhibit D-BHB from entering cells.

Ketone esters are the free form of BHB (i.e not attached to a salt or other compound) and raise ketones to a greater degree than ketone salts but are typically more expensive, have a terrible taste and can cause GI distress.

It is important to note that ketones are not weight-loss supplements, as they are an energy source. They may help with weight loss indirectly through appetite suppression, improving insulin sensitivity and increasing brown adipose tissue.

How much: Typically one serving in the morning if you’re having a busy day and require optimal alertness. I use them as needed, for energy dips or hunger pangs. Sodium-BHB appears to be the superior salt, and it is important to look for the bioactive form of BHB: D-BHB.


Why take it: Magnesium, potassium, calcium, phosphorus, and sodium are the 5 key electrolytes in the body. Arguably, the most important is sodium, which makes up 80-90% of what is lost in sweat. Additionally, insulin increases sodium reabsorption in the kidneys, and because insulin is very low while fasting, sodium retention is much less than usual, making supplementing extremely important. Just like replenishing electrolytes is so important on the keto diet due to limited carbohydrates, it is even more important when fasting. It is very common to see deficiencies which lead to hyponatremia, especially in athletes.

Electrolytes during fasting

Electrolytes help to maintain cellular hydration, but more interestingly, is the role of electrolytes as ionic molecules that play a big role in the body-electric. Our cells are electrically charged due to the concentration of these minerals on the inside and outside of our cells creating a concentration gradient, and it is this charge that is responsible for all of our cellular reactions.

How much: I recommend a dose of sodium is around 5g per day, while fasting. Add salt to your water, and look for unflavoured, unsweetened electrolyte powders. Throughout the day, I add salt to my water, and magnesium glycinate, and add an electrolyte powder if needed.

Apple Cider Vinegar

Why take it: ACV is a good fat emulsifier, but is also effective for regulating blood sugar and suppressing appetite, making it a great fasting companion. It is often used to improve digestion, so having this in the early stages of the fast and when you are reintroducing food after the fast is a good idea too.

How much: 1 – 2 Tbsp can help to flavor your water and can reduce your cravings.


Why take it: Over 300 critical enzymatic reactions in the body use magnesium as a cofactor, such as muscle contraction and relaxation, heart rhythm, nerve function and even bone formation. Magnesium is critical in many ATP-generating reactions, and thus our energy levels depend on its presence. If we can support these reactions while fasting through supplementation, we are likely to feel stronger and more energized. It also has a calming effect, as magnesium regulates muscle relaxation and helps to shift you from a sympathetic state to a parasympathetic state. Lastly, it is required for the synthesis of serotonin from tryptophan making it essential for a good mood!

How much: About 300-450mg/day is recommended. Forms to avoid are magnesium carbonate and magnesium oxide. More bioavailable forms include amino acid chelates or krebs cycle intermediates like magnesium glycinate, threonate or succinate.

Other considerations

If you plan to exercise

Branched-chain amino acid (BCAA)/essential amino acid (EEA) supplementation will technically break a fast, however, if you’re considering working out, and want to ensure that you’re not tapping into muscle tissue for energy while in a hypocaloric state (where you’re highly likely looking for any source of energy), then supplementing with AA may be optimal. If you’re keto-adapted, you will probably have elevated blood BHB levels and BHB is anti-catabolic, but on an extended fast, it makes a lot of sense to use a supplemental form of amino acids to prevent any muscle catabolism. If your goal is to stimulate autophagy, then it is better to avoid high intensity exercise where you need AA supplementation.

You’re struggling to sleep

L-Theanine has a calming effect by putting the brain into an alpha brain wave state. The L-isomer is the biologically active form.

Melatonin is the hormone that regulates the sleep-wake cycle. Hormonal and neurotransmitter alterations can occur when vastly changing your caloric intake, leading to poor sleep. It can help to supplement with melatonin as you may be acutely deficient in it.

To enhance detoxification

Curcumin has been shown to have potent antioxidant and antiinflammatory effects, and is helpful for regulating blood sugar and improving gut health. More bioavailable forms such as Curcuwin are good to look out for.

N-Acetylcysteine (NAC) is a precursor to glutathione, the master antioxidant of the body. The acetylated form makes it optimized for conversion.
Liposomal glutathione, the most bioavailable form of glutathione, is a potent antioxidant. Glutathione supplements that are not liposomal are easily broken down into its 3 amino acids, cysteine, glycine, and glutamate, making liposomal NAC a better choice.

So there you have it; my supplement suggestions while fasting. I do want to stress the fact that I don’t necessarily take all of these while I’m fasting. I tend to judge how my energy levels are and how my mood is and add in supplements only if I really need to. I believe supplements are an option, and can be extremely useful for first timers. This is where self-experimentation comes in so that you can find out what works for you. Depending on your goals, you can use one or none of these; they’re here just for you to consider to enhance your results. If you’re the hard charger who wants to dry-fast, then go for it, but these supplements are probably not for you. For safety reasons I’d not recommend doing extended dry fasts on your own.

If you’re on any medication you should continue this, or consult a doctor before changing any medications or adding in any supplements.

Please leave any questions and comments you have below! I’d also love to know if you have tried any of these supplements or if you have any others that you have tried and found to be useful.

If you want to dive deeper into the world of supplements and discover the truths behind all the lies you’ve been told about supplements, then check out this NEW docu-series by Revealed Films called Supplements Revealed!

This is an incredible series of documentaries that are extremely well put together. It will uncover all the myths and confusion you have of the supplement industry as all of the top experts in the space are interviewed.

You can claim your free invite here, and please share this with your friends and family – this could change their lives. The more you are educated, the greater your ability to make better decisions to optimize your health.

Lastly, keep an eye out for detailed lists of my top supplements for keto, longevity, performance, sleep etc. – Make sure you are subscribed to my newsletter to stay up to date!

Any questions? Comment below!

Stay healthy.


  1. claribel lopez says:

    Which supplements are good for treating leg cramps especially at night ???

    • Kirsten Flanagan says:

      Hi Claribel
      Magnesium is great for muscle relaxation. Look for forms like magnesium threonate, glycinate or citrate. Also make sure that you’re having adequate amounts of the other main electrolytes like sodium, potassium, calcium. You can find formulas with all of these in them, but it is a good idea to salt your meals generously with good Himalayan or Celtic sea salt (RealSalt is a great brand).
      Keep drinking filtered water, to thirst, too.

      Hope this helps.

  2. Irene Silva says:

    Can i take hemp oil to telax during fasting?

    • Kirsten Flanagan says:

      Hi Irene, yes – I don’t think there would be any negative effects on your fast by taking hemp oil.

  3. Jane Bernal says:

    I would like to order a multivitamin from you how do I order

    • Kirsten Flanagan says:

      Hi Jane,
      I don’t have any products myself. I would recommend BioTrust and Thorne. Thanks!

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