Quick answers
Do vitamins break a fast?
Gummies, chewables, protein powders and collagen do. Medication is a different matter: ask your doctor
Take them with a meal
The simplest rule is to take supplements in your eating window. Fat-soluble vitamins such as vitamin D are also better absorbed with a meal, so you lose nothing by waiting. Protein powders and collagen raise insulin like any protein 1,2, so they belong in your window too.
What's fine during a fast
- Water, black coffee and plain tea.
- A pinch of salt or sugar-free electrolytes, mainly on fasts of 18 hours or more 3.
- Your usual medication, as prescribed.
- MYTH
- Everyone who fasts needs electrolyte supplements.
- FACT
- For daily fasts of 12 to 16 hours, there's no evidence that supplements are needed. You eat every day, and your meals replace what you lose. They become more useful on fasts of a day or longer, in the heat, or with heavy exercise.
Sources
- Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997;66(5):1264-76. doi.org/10.1093/ajcn/66.5.1264
- Nilsson M, Stenberg M, Frid AH, et al. Glycemia and insulinemia in healthy subjects after lactose-equivalent meals of milk and other food proteins: the role of plasma amino acids and incretins. Am J Clin Nutr. 2004;80(5):1246-53. doi.org/10.1093/ajcn/80.5.1246
- Sigler MH. The mechanism of the natriuresis of fasting. J Clin Invest. 1975;55(2):377-87. doi.org/10.1172/JCI107941
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873
Keep reading
What breaks a fast (and what doesn't)Coffee, milk, sweeteners and supplements, judged by what they do to your body- Does a protein shake break a fast?Yes, clearly. Protein raises insulin, and whey more than most. Have your shake in your eating window
Water, salt and electrolytesWhy fasting changes how your body handles water and sodium, and when it's worth doing something about it
A note on health
Fasting Tracker is designed for general wellness and is not a medical device. Fasting is not right for everyone. If you are pregnant, diabetic, have a history of eating disorders or take medication, talk to your doctor first, and before any extended fast.