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Which Nutritional Supplements Do You Really Need When Fasting?

Which Nutritional Supplements Do You Really Need When Fasting?

Water fasts, juice fasts, intermittent fasts, alternate-day fasts… It’s safe to say most of us have tried – or know someone who has tried – fasting.

Fasting is generally pursued for health reasons, as it has been shown to aid weight loss and even boost cognitive performance. That said, there are many other valid reasons why you might consider fasting, whether on a short- or longer-term basis.

Of course it is counterproductive to fast if doing so brings its own problems, particularly related to nutritional deficiencies, and so some smart supplementation should be considered. And not just to plug dietary gaps either, but to increase the efficacy of the fast itself.

In this article, we shall summarise some of the most common questions surrounding the topic of supplementation during fasting.

Is Supplementation Necessary? It Depends

There is no easy answer to this question because it very much depends on your state of health, diet, age, sex, stress levels and so on. It also depends on where you’re at before starting the fast.

For example, are you deficient in one or several nutrients prior to commencing the fast? If so, the problem will only be exacerbated.

Certain nutrients are of particular importance to specific people. For example, the average intake of vitamin A and vitamin B9 has fallen below even the Lower Reference Nutrient Intake (LRNI) among females in recent years.

There has also been a general reduction in iron intake across the board according to results from the latest National Diet and Nutrition Survey (NDNS). What’s more, those with darker skin have a greater need for vitamin D supplements.

If you are in the habit of following a typical western diet, you are in all likelihood deficient in a swathe of important vitamins and minerals, not to mention omega-3s and fibre.

Of course, fasting may necessitate some form of supplementation even if you eat a perfect diet.

Water-soluble vitamins such as vitamin C and B-complex vitamins, for example, cannot be stored in the body – and therefore must be regularly sourced daily from the diet. (If you consume a surplus, the remainder will be excreted in urine.)

Contemplating a fast? We would encourage you to read The Scientific Pros and Cons of Fasting.

Our in-depth guide details the various types of fasts, the scientific benefits thereof, and also pitfalls to be avoided.

Do Supplements Break a Fast?

This has to be one of the most common questions posed by fasting dieters. After all, while many of them are understandably eager to top up their nutrient levels in pursuit of peak performance, they do not wish to break their fast to do so.

The answer is entirely the same: it depends. Whether a supplement breaks your fast is dependent upon the product in question, and the burden it places on the digestive system.

While a 200-calorie protein shake will definitely break your fast, supplements in regular capsule or tablet form are unlikely to break a fast, since they are non-caloric or, at the very least, very low in calories. This includes fish oils, multivitamins, creatine and probiotics.

One thing to bear in mind is that some supplements rely upon co-factors from food for proper absorption.

For example, vitamins A, D, E and K are better absorbed in the presence of fat. And so if you are supplementing with those, it is best to do so alongside food.

You should also be mindful of the fact that medication can reduce the body’s ability to absorb calcium and vital B vitamins.

So depending on the medication you use, you may have a special need for certain supplements, whether before, during or after fasting.

Useful Supplements to Take When Fasting

  • Vitamins

In an ideal world, you should source all the vitamins you need from your diet. But some fasts make it difficult to achieve this.

For example, if you are performing an alternate-day fast, you will have to pack two days’ worth of vitamins into one eating window.

Not an easy feat considering some of us struggle to hit our D3 and B12 quotas even when pursuing a broadly healthy diet.

Using a good-quality multivitamin is a sensible approach for most people. Revitacell Mega Multi is a vegan multivitamin mineral complex with fulvic and humic trace minerals to aid absorption and for detoxification. 

For best results, pop a tablet during your eating window. You might want to take it during your final pre-fast meal.

  • Minerals

Minerals are every bit as important as vitamins. In a sense, they’re even more important.

When it comes to fasting, bear in mind that extended-period fasting can cause dehydration and depleted electrolyte levels.

Mineral electrolytes assist in the regulation and maintenance of various bodily functions, interacting with one another as well as cells in muscles and nerves.

The key electrolytes are sodium, potassium, magnesium, zinc and calcium. Deficiencies of one or several electrolytes can set the scene for extreme fatigue, heightened anxiety, insomnia, low stomach acid and headaches.

Ronald et al. (14) observed that fasting, coupled with physical activity, results in greater energy consumption, perspiration and dehydration which can presage malnutrition and electrolyte imbalance.

In a further 2013 study of females fasting during Ramadan, potassium in particular “decreased significantly” during the period.

Cardiovascular research scientist Dr. James DiNicolantonio noted in his best-selling book The Salt Fix that “low-carb as well as intermittent (and especially prolonged) fasting diets cause massive losses of sodium and water from our kidneys and increase our need for salt.”

He went on to observe that “prolonged fasting on top of a low sodium intake pulls sodium from body stores (such as bone) to replenish the exchangeable sodium space. In essence, prolonged fasting, especially on top of low sodium intake, may put patients at risk of osteoporosis, as sodium is an important component in bone formation and seems to be depleted while fasting.”

You probably want a supplement that won’t knock you out of your fast, in which case Progurt’s multi-mineral Chloride is a fantastic option. It combines four highly absorbable ionic mineral chlorides – sodium, potassium, magnesium and calcium – and can be added to water and drunk. Each bottle supplies 100 servings.

You might consider consuming prior to a fast, or taking during an eating window.

  • MCT Oil

MCT oil is particularly popular with those who practice Intermittent Fasting. The reason is because MCT oil suppresses hunger and gives the fasted body a boost, ensuring it can manage long hours of starvation.

MCT oil is typically utilised in black coffee to make the popular “Bulletproof Coffee” which helps keto dieters get through the day.

If you are not particularly struggling with energy levels during your fast – after all, the fast may not be long enough to provoke fatigue – there is really no need to take MCT oil. However, some people swear by it.

Skip MCT oil powder, which usually contains 50-100 calories per serving, and choose MCT oil capsules instead.

Divine Health’s MCT Softgels have just 8 calories yet provide 1g of medium chain triglycerides, divided between smaller molecular C8 chains (55%) and longer C10 chains (40%).

They won’t break your fast but they’ll provide a welcome source of clean-burning fuel for the brain, muscles and other tissues.

  • Ketones

Like MCT oil, ketone supplements should not be considered essential during a fast.

However, certain fasting dieters appreciate their ability to provide a source of clean-burning fuel while helping the body stay in ketosis.

Ketone supplements are known as fast-mimicking supplements, because they actually trick the body into believing it is in ketosis. Ketone supplements may also mitigate the unkind effects that transitioning into ketosis brings about.

Dr. Peter Attia has written about his experience with ketone supplements, specifically as they pertain to energy expenditure and fat oxidation.

His conclusion? “BHB (a ketone supplement) produces more ATP per unit carbon and per unit oxygen consumed than glycogen and free fatty acid.”


The dietary supplements we’ve covered in this article are not the only ones associated with fasting. Others include BCAA’s, black seed oil, fibre supplements, creatine, protein and herbs.

However, we would strongly argue that we have covered the most valuable supplements for fasting purposes. While the others may help, they are not strictly necessary.

It is self-evident that fasting will result in a reduced intake of vitamins and minerals, so these must be prioritised. MCT oil and ketones are somewhat optional – though they can be helpful for many people, depending on the nature of your fast and how your own body operates.If done properly, fasts can be very beneficial for our health.

Water for Health Ltd began trading in 2007 with the goal of positively affecting the lives of many. We still retain that mission today because we believe that proper hydration and nutrition can make a massive difference to people’s health and quality of life. Click here to find out more.

The take-home? Fasted athletes or active people may benefit most from ketone supplements, due to more efficient physical performance.