There are lists in my book, Delay, Don't Deny, that are quite specific about things you should and shouldn't have while fasting. Black coffee, plain water, unflavored sparkling water, plain teas...all are safe. Anything that tastes sweet is NOT safe. But would it surprise you to know that there is a grey area in the middle?
The issue is that we are all different, and our bodies may not all release insulin in response to the exact same things. Some items are never a good idea: anything that tastes sweet is an immediate no-no. We know that we should avoid all artificial sweeteners, and even "natural" sweeteners that proclaim that they are "GREAT FOR DIABETICS!" or "Low-glycemic!" or "Won't raise blood sugar!" (Remember: we are worried about raising insulin, not blood sugar. That confuses a lot of people. Sweet tastes raise insulin levels, not blood sugar. In fact, if your body releases insulin, you would actually expect to see your blood sugar go DOWN as insulin does its job--which is to lower your blood sugar. I have had many people argue that a particular artificial sweetener is fine for them because they tested their blood sugar after consuming it and their blood sugar didn't go up. Of course it didn't! Insulin lowers blood sugar. It also stops the fat burning process, which is why we want to avoid it during the fast.)
The items in the grey area include things like various herbal teas, lemon wedges, apple cider vinegar, and the like. When you ask, what about this tea, or that tea, or lemon wedges, or apple cider vinegar in water, or.....? I can't give you a definitive list of what is okay, because the answer isn't the same for everyone.
Some people do well with lemon wedges in their water, or a bit of Apple Cider vinegar throughout the day. Others don't. You are going to have to do some experimenting to find out for yourself.
Here is how you will know what works for you and what doesn't. First, you need to fast "clean" for awhile. By fasting "clean", I mean nothing but plain black coffee, plain water, plain sparkling water, and plain black or green tea during your daily fasting time. Give yourself two to three weeks to see how your body feels during the daily fast. At the end of that time period, you will be familiar with how your body feels during the day while fasting, including your daily levels of hunger. (And NO, I do not mean that you should fast nonstop for 2 or 3 weeks straight..I'm an intermittent faster, NOT an extended faster. What I mean is that you should follow your preferred intermittent fasting routine for at least 2 weeks, fasting clean during the fast and then enjoying your eating window each day. That should be enough time for you to know how your body feels during the fasted part of the day.)
At that point, try whatever it is that you are questioning. That certain tea that you aren't sure about. Lemon wedges. Apple Cider Vinegar. Whatever it is you think might be okay, but aren't sure about.
If the item is okay for you, you won't notice any difference in hunger or energy levels. You'll feel the same as you did when fasting clean. If that happens, congratulations! That item is fine for you.
If the item is not okay, you will know very soon. You'll feel shaky or hungry within about an hour (if not sooner), and it will be harder to fast. This is why it is so important to fast clean for a couple of weeks first. When you are used to fasting, you can tell when something doesn't work for you because you are in-tune to your body.
Once, I had a very noticeable reaction to some strawberry flavored mineral water. The only ingredients were mineral water and "natural strawberry flavor." Within an hour, I was shaky and STARVING. I knew right then that my body is very sensitive to fruit flavors, and I have avoided them ever since.
I also can't handle apple cider vinegar. It makes me noticeably hungry. Others drink it all day long while fasting (a T or so diluted in water, hot water, or sparkling water) and do just fine. Some people tolerate lemon water. Some don't. You get it.
The moral of the story is: when it comes to items in the grey area, no one can tell you 100% what will work for YOU during the fast. You have to learn that for yourself.
And NO--this is not an excuse to try to work in your favorite Diet Soda. This one is easy: sweet=no. EVERY TIME.
Gin Stephens lives in Augusta, Georgia, where she has been following an intermittent fasting lifestyle since 2014. In addition to writing the book Delay, Don't Deny, Gin is co-host of The Intermittent Fasting Podcast, along with fellow intermittent faster and author, Melanie Avalon. Check out www.ifpodcast.com or search for The Intermittent Fasting Podcast on iTunes.