Can You Take Supplements While Fasting? What You Need to Know
By: Dave Asprey
- When you fast, your body burns fat and detoxes your cells.
- If you’re a fasting purist, you drink only water during your fast. If you follow Bulletproof Intermittent Fasting, you can consume fat, but avoid protein and carbs. Whichever fasting method you follow, the question remains: Can you take supplements while fasting and still reap the benefits?
- Certain vitamins and medications are meant to be taken with food. Take them during your eating window. Some prescription drugs are time-sensitive. Ask your doctor before you try intermittent fasting.
- If you’re doing Bulletproof Intermittent Fasting, which allows fats, then have fat-soluble vitamins with your Bulletproof Coffee. I take Vitamins A-D-K, Eye Armor, and Omega Krill in the morning with my coffee.
Intermittent fasting improves your focus, torches body fat, and gives aging the middle finger.
It does this by promoting autophagy, the process through which your cells get rid of built-up waste. Fasting also causes your gut bacteria to secrete a protein called fasting-induced adipose factor (FIAF), which signals to your body that it’s time to burn fat.
The benefits of fasting end when you fill your belly with a tasty meal — but what about vitamins and coffee? Can you take supplements during your fasting periods and still benefit from them?
I see this question all the time. Here’s what you should know once and for all about taking supplements while fasting.
RELATED: Set yourself up for intermittent fasting success — instantly download the Ultimate Intermittent Fasting Guide to get your quick-start guide, sample 3-day meal plan, and printable intermittent fasting journal.
Can I take supplements while fasting?
There’s no black-and-white answer here. Whether or not you can take a supplement during your fast depends on what pills you take and how your body responds.
I’ll go into more detail about the most common supplements below. With a few exceptions, I recommend going the biohacker route: Try the supplement during your fast and see how you feel.
Vitamins and fasting
Taking vitamins while intermittent fasting requires some experimentation. Fortunately, that’s what biohacking is all about.
In The Bulletproof Diet, I recommend 10 basic supplements that everyone should take to provide their bodies with essential nutrients that are missing from most diets. Certain supplements, like curcumin and krill oil, are easier for your body to absorb when they’re taken with food. So, have them during your eating window (or with your Bulletproof Coffee). It’s that simple.
If you only have water or just black coffee during your fast, a lot of vitamins — especially B-vitamins — can make you want to hurl. If you feel foggy, shaky, or queasy when you take your vitamins on an empty stomach, change your schedule so you take them when you eat.
Here are a few quick points to keep in mind:
- Fat-soluble vitamins: On a plain water fast, take them during your eating window. With Bulletproof Intermittent Fasting, you can take fat-soluble vitamins with your Bulletproof Coffee. I have Vitamins A-D-K, Eye Armor, and Omega Krill Complex with my morning coffee.
- L-tyrosine: No worries here — this is meant to be taken on an empty stomach. Learn more about the benefits of L-tyrosine.
- Amino acids: L-glutamine and branched-chain amino acids (BCAAs) are usually a no-go because they can kick you out of ketosis by raising your insulin levels. If you want to take these supplements while staying in ketosis, add Brain Octane Oil, which supplies your body with extra ketones.
- Chromium and vanadium: These minerals can actually drop your blood sugar levels too low while you’re fasting. If your insulin levels dip, you run the risk of hypoglycemia — aka low blood sugar. As I say in my conversation with Dr. Julie Holland on the Bulletproof Radio podcast, even a small bout of hypoglycemia can lead to problems adjusting and managing your moods. So, skip these supplements during your fast.
Want to learn a secret? When you follow a nutrient-dense, low-toxin diet like the Bulletproof Diet, it’s easier to stabilize your blood sugar levels and stay in autophagy during fasting periods. The Bulletproof Diet reduces your exposure to insulin-spiking junk, and it fills your plate with foods that provide your body with essential micronutrients.
It also makes fasting easier because you start your day with a rich, delicious cup of buttery coffee — more on that later.
Medication and fasting
Talk to your functional medicine doctor before you mix fasting with prescription drugs. Some medications have to be taken within specific timeframes, and taking them on an empty stomach or within restricted eating windows can mess with their effects. If your prescription drugs aren’t time-sensitive, take them during your eating window.
If you have to temporarily step away from intermittent fasting because of your medication, that’s okay. You can still upgrade your performance (and even reverse your symptoms of some conditions) by switching to a high-fat, low-toxin diet to reduce your whole-body inflammation. Learn more about diet-induced inflammation in this episode of the Bulletproof Radio podcast.
Related: How to Reverse Diabetes Without Medication
Caffeine and fasting
Caffeine isn’t technically a supplement, but it does have vitamin-like powers. It turns out that caffeine improves memory recall and has antioxidant effects. And, of course, coffee has been shown to boost your mood, improve your focus, and reduce your risk of chronic degenerative disease. Learn more about the benefits of coffee and caffeine.
During your fasting periods, you can drink black coffee, no matter what intermittent fasting method you follow And if you follow Bulletproof, you can drink Bulletproof Coffee (aka butter coffee) during your intermittent fast. If you don’t drink java but still want caffeine, drink high-quality green tea. Avoid black tea, which is fermented and increases your risk of mycotoxin exposure.
Fasting purists say that consuming anything but water breaks your fast. I’ve done water-only fasts. They aren’t fun. In 2008, I spent 4 days on my own in a cave 20 miles outside of Sedona, Arizona. I meditated and only consumed water, and I lost 14 pounds because my body literally began to eat itself.
It was a transformative experience and an extreme example of the fat-burning benefits of IF — but obviously, it’s not for everyone. In the real world, water-only fasts leave you cranky, tired, and unfocused.
That’s fine if you’re in a cave. Not so much if you have to go to work and talk to people.
That’s where Bulletproof Coffee and intermittent fasting come in. When your body burns fat instead of carbs, you produce ketones. Because it’s made with Brain Octane Oil and grass-fed butter or ghee, Bulletproof Coffee helps your body produce ketones quickly, and the fats help you feel full for hours. Learn more about Bulletproof Coffee and intermittent fasting.
On the Bulletproof Diet, you start your morning with a cup of rich, buttery coffee. You won’t think about food during your fast, and you won’t feel like garbage when you’re fueled by ketones, not fumes. And because your body processes fat differently than carbs or protein, your liquid breakfast won’t interrupt autophagy.
So, you can still benefit from fasting without feeling cranky — and without spending time in a cave.
Why coffee and intermittent fasting belong together
If you want to supercharge the benefits of fasting, here’s another reason you should supplement your IF with coffee.
In The Bulletproof Diet, I write about mTOR stacking. mTOR stands for “Mammalian Target of Rapamycin,” and it’s all the rage in anti-aging circles. When your mTOR levels go up for brief periods of time, you build muscle. I talk about this process in my conversation with exercise scientist John Kiefer on the Bulletproof Radio podcast.
There are three things that increase mTOR: exercise, coffee, and intermittent fasting. Bulletproof fasting combines all three into a “stack” so you can spike mTOR three times as much, and you’ll get more muscle-building results from your workouts. Learn more about mTOR stacking.
This is all based on original research published in “The Bulletproof Diet” in 2014. If you’re specifically doing intermittent fasting to put on muscle, you should absolutely have coffee before you exercise because it’s going to give you better results. Period.
A note about FIAF
Remember fasting-induced adipose factor (FIAF) from “The Bulletproof Diet”? Your liver makes this protein when your body is in a fasted state. It uses FIAF to burn fat when you need energy. Gut bacteria have figured out that they can hack your system by making their own FIAF to burn fat when you’re fasting, too.
According to a 2015 review, scientists don’t yet know the impacts of fats and protein on gut bacteria. So, if you have fat during a fast, there’s a chance you’re going to have less of a FIAF effect than a water fast alone.
However, this trade-off pays big dividends in the long-run because you’re introducing a lot of good stuff into your system when you start your day with Bulletproof Coffee.
The Brain Octane Oil in Bulletproof Coffee is a strong antifungal, antibacterial, and antiviral.  Coffee contains polyphenols, which feed the good bacteria in your gut. And grass-fed butter contains butyrate, a fatty acid that increases fat burning and makes your mitochondria happy.
The bottom line is, yes, you can use supplements while you’re fasting. If your vitamins and medication upset your stomach or need to be taken with food, take them during your eating window. A lot of supplements modulate your gut bacteria, so pay attention to how you feel after you take them. Find what works for you and helps you thrive.
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