Fasting is something that people have been doing for centuries. Our ancestors practiced fasting during periods of food scarcity, but they also practiced intermittent fasting during periods of abundance, as the food they consumed was much more nutrient-dense than what we consume today, meaning it sustained them for substantially longer periods than the carb-rich meals we typically eat. While fasting has been practiced for hundreds, if not thousands of years in several different religions, the fasting we do today is typically promoted for its long list of health benefits.
Be it increased energy production and better athletic performance, or enhanced detoxification and sharper brain function, the benefits of abstaining from food span far beyond weight loss. So, we’re breaking it down for you. We’re talking about what fasting is and why people do it, how supplements can still be a part of a fasting protocol, and what’s safe to take and what’s not during a fast. Let’s get to it.
What Is Fasting And Why Do It?
As we said, fasting is a practice that’s been around for centuries. Fasting was practiced in ancient Greece in preparation for many rituals that sought contact with supernatural forces; the Old Testament saw fasting as a powerful prayer that could prepare a prophet for divine revelations.
Jesus Christ fasted for 40 days in the desert; and in the mid-1800s, B. H. Dewey, MD, in his book The True Science of Living, wrote, "every disease that afflicts mankind [develops from] more or less habitual eating in excess of the supply of gastric juices” 1. More recently, however, we’ve caught onto the benefits of fasting for health, and while we don’t typically tend to engage in fasts for 20, 30, even 40 days, we gravitate more towards what we call ‘intermittent fasting’—the idea of rearranging your eating window to go anywhere from 16 to 20 hours without food. And the reason why intermittent fasting has become so popular among health and wellness gurus is not only for the profound benefits it provides, but also because it offers up a great deal of flexibility; there isn’t just one way to do intermittent fasting, so it can easily fit into most people’s schedule. Here are a few of the most popular options:
- Complete alternate-day fasting: Involves alternating fasting days (no energy-containing foods or beverages can be consumed) with normal eating days
- Modified fasting: Allows 20–25% of energy needs to be consumed on scheduled fasting days (usually around 500 calories)
- Time-restricting feeding: The most popular method of fasting (i.e. intermittent fasting), whereby you consume your daily energy intake within a specific time window over 24 hours.
Time-restricted feeding is by far the most popular type of fasting practiced by people worldwide, and there’s a large body of evidence backing its efficacy for improving several parameters of health.
It’s been associated with reductions in body weight, total cholesterol levels, triglycerides, glucose, insulin, interleukin-6 (IL-6), and TNF-α, as well as improvements in insulin sensitivity 2. But that’s not it. Intermittent fasting has also been shown to:
- Alter function of hormones, cells, and genes
- Stimulate autophagy (cellular clean-up)
- Improve metabolic markers
- Enhance weight loss
- Reduce inflammation
- Improve athletic performance
- Enhance cognition and reduce brain fog
In no way is this an exhaustive list of the benefits associated with fasting, but it gives you a good idea as to why people are going crazy over it.
Can I Take Vitamins While Fasting?
One of the big questions that comes up with fasting is what can I eat or drink? and while water is generally your safest best for liquids and food is a complete no-no, what about supplements? Can you take those during a fast or should they be consumed during your feeding window? This isn’t a straightforward answer because there’s a lot of variation within and between supplements, which means some may be safe to take while fasting while others are a definite no.
As a general rule of thumb, any supplement with a caloric value attached to it has the potential to break a fast, but also any supplements that will provoke an insulin response.
So, that’s any supplement that has an artificial or natural sweetener in it. For example, gummy vitamins are one that you may think are safe to consume during your fast, but they will trigger the release of insulin, which essentially will kick you out of ketosis and autophagy. However, you also want to consider what vitamins should be taken with food and which shouldn’t.
Fat-soluble vitamins (vitamins A, D, E, and K) are typically recommended to be consumed alongside a meal with fat to maximize absorption, while water-soluble vitamins (B-complex and vitamin C) are generally okay to take without food, although B vitamins can cause nausea for some people on an empty stomach.
Best 6 Vitamins to Take During Fast
Electrolytes (sodium, magnesium, potassium)
Electrolytes like sodium, potassium, magnesium, and calcium are required for several key body processes, including muscle contraction, fluid balance, nerve conduction, and more. If you’re training in a fasted state, electrolytes are lost through sweat, but imbalances in minerals can also lead to feeling lightheaded or dizzy.
As well, because fasting often involves drinking large amounts of water to maintain hydration, you want to ensure you’re balancing that out by adding minerals back in. Whether it’s in the form of an unsweetened pure electrolyte beverage or purchasing powdered versions of the minerals, find a way to get them in during your fast. Magnesium is a common deficiency for a lot of people and plays a role in more than 300 biochemical processes in your body that regulate energy production, muscle function, bone growth, protein synthesis, and more 3.
And because a magnesium deficiency can affect calcium and potassium levels in the bloodstream, you can start to experience things like muscle cramps, fatigue, irregular heartbeat, digestive symptoms, and weakness. Sodium and potassium also play key roles in muscle and nerve function, energy production, and regulating blood pressure and volume. Electrolytes do not contain calories, which means they don’t stimulate pro-growth pathways like mTOR, which is activated by carbs or insulin, and branched-chain amino acids, so they should be safe to consume during a fast—assuming they’re in the pure form.
Water-soluble vitamins (B-complex + vitamin C)
For the most part, any pure forms of nutrients will not disrupt ketosis or break a fast, and the same is true for the B vitamins and vitamin C.
The B vitamins are a group of 8 water-soluble vitamins that play a major role in energy production, metabolism, hematopoiesis (blood cell formation), cognition, nerve function, hormone balance, and much more 4. They also play a major role in supporting cellular functioning, as they act as co-enzymes in a wide array of catabolic and anabolic enzymatic reactions. Vitamin C, on the other hand, is a vitamin essential for proper immune function contributing to the cellular function of both the innate and adaptive immune system 5. It also acts as a powerful antioxidant alongside vitamin E to protect cells against oxidative stress.
Creatine
Creatine is a staple for a lot of athletes due to its role in muscle growth and energy production, and it’s one that’s safe during your fast. Does creatine break a fast? If you’re training during your fast, creatine can help increase energy supply through enhanced generation of ATP. The body uses creatine phosphate stores during high-intensity activity, such as lifting, jumping, and sprinting, but adding in creatine can help to support maximum physical effort since your body cannot depend on the breakdown of carbohydrates to provide energy in a fasted state.
As such, having more creatine phosphate in muscle tissue means faster ATP generation, which can result in greater gains in strength, power, speed, and muscle growth—even during fasting or caloric restriction. And because creatine is free of calories and does not contain anything that will trigger an insulin response, it will maintain a fasted state 6.
Iron
Iron is a supplement that isn’t common to a lot of people’s supplement stack because most people obtain sufficient amounts through diet, but if you’re someone who struggles with low iron stores or are a menstruating female, you’re in the clear to take your supplement during a fast. Because iron is best absorbed on an empty stomach in combination with vitamin C, take it during periods of fasting or before meals. However, some people can experience minor digestive upset, cramps, or constipation, and if you find this to be the case, consume your iron supplement with your first meal of the day during your feeding window.
L-tyrosine
If you want to avoid some of the fogginess that can come with fasting, L-tyrosine is a good one to add to your fasting stack. It’s an amino acid that’s your brain converts into three important neurotransmitters that play a critical role in the stress response and mood:
- Dopamine: Plays a major regulatory role in mood and is involved with the reward center of the brain.
- Norepinephrine: Supports the body’s stress response and muscle recovery.
- Epinephrine: Plays a role in motivation and focus.
While L-tyrosine is technically an amino acid and amino acids can break a fast, taken in low doses, it shouldn’t elicit any sort of response.
Probiotics and prebiotics
These guys are a necessity for supporting good gut health and everything that stems from a healthy microbiome, and they get the thumbs up for taking during a fast.
Some bacterial strains are designed to be taken on an empty stomach when stomach acid levels are low and won’t interfere with function, however, check the label on your supplement to be sure.
Related Post: Does Prebiotic Fiber Break a Fast? - A Complete Guide
Top 4 Supplements to Avoid
Some of the supplements that are not advised to consume during a fast are:
Omega-3s (algae oil, fish oil, cod liver oil)
Because fish oils are pure fat, watch how much you’re taking. Any more than one tablespoon (15g) means you’re treading into risky territory.
Multivitamin
A multivitamin may not have a caloric tag, but many of the nutrients in them are best absorbed with food. So, while you can take it during your fasting window, you may find that leaving it for your feeding window means nutrient absorption is better.
Protein powder
Protein should be avoided at all costs during fasting. Not only does it have calories but any sort of “whole foods supplement” will 100% break a fast. The same goes for any supplements containing collagen peptides.
BCAAs
Many people choose to take BCAAs when doing fasted training, but technically amino acids will trigger an insulin response and therefore stop both autophagy and your fast 7.
With that said, BCAAs are generally recommended for fasted training to prevent muscle catabolism, but something like HMB that doesn’t trigger an insulin response would be better suited for maintaining muscle mass in a fasted state. The last thing we want to hit on is that any supplement containing sugar—natural or artificial (pre-workouts included)—should be avoided during a fast, as it will trigger insulin release. So, be mindful of what the ingredients are in your supplements and if you’re not sure, wait until your feeding window.
Final Thoughts
Long story short, several supplements are okay to take during a fast, but you have to pick and choose what works and what doesn’t.
If the ingredients are anything but a pure vitamin or mineral, chances are it’s better kept for your feeding window to avoid stopping autophagy and kicking you out of your fast.
References
- PR Kerndt, JL Naughton, CE Driscoll, DA Loxterkamp. Fasting: the history, pathophysiology and complications. West J Med. 1982;137(5):379-399.
- RE Patterson, GA Laughlin, AZ LaCroix, et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015;115(8):1203-1212.
- W Jahnen-Dechent, M Ketteler. Magnesium basics. Clin Kidney J. 2012;5(Suppl 1):i3-i14.
- DO Kennedy. B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review. Nutrients. 2016;8(2):68.
- AC Carr, S Maggini. Vitamin C and Immune Function. Nutrients. 2017;9(11):1211.
- B Gualano, RB Novaes, GG Artioli, et al. Effects of creatine supplementation on glucose tolerance and insulin sensitivity in sedentary healthy males undergoing aerobic training. Amino Acids. 2008;34(2):245-250.
- MS Yoon. The Emerging Role of Branched-Chain Amino Acids in Insulin Resistance and Metabolism . Nutrients. 2016;8(7):405.
