Does multivitamin break a fast?

A multivitamin tablet or capsule holds small amounts of vitamins and minerals and almost no energy. In the US, a supplement label must show calories once a serving has 5 or more. So if your tablet's label has no calorie line, a serving has under 5 calories.

That keeps all four of this site's goals intact: weight loss, autophagy, gut rest and blood sugar. A tablet is not a meal for your gut to work on, and with almost no calories it does not lift blood glucose.

Gummy multivitamins are a different product. Read the ingredients. When sugar or glucose syrup (corn syrup) is listed, the gummy breaks a fast for blood sugar, autophagy and gut rest. Treat it like a small sweet.

Taking a tablet with a meal can still be the better choice. Vitamins A, D, E and K dissolve in fat. In a study of 50 older adults, one dose of vitamin D3 taken with a meal containing fat gave 32% higher blood levels. The comparison was the same dose with a fat-free meal. That is early evidence from one short study.

Check whether your multivitamin contains iron. High doses of iron (over 20 mg) can make you feel sick or cause stomach pain. If yours does that on an empty stomach, move it to your eating window. Keep iron supplements out of children's reach, as very high doses can be fatal for them.

If you also take a separate vitamin D supplement, add the two together. Adults should not take more than 100 micrograms (4,000 IU) of vitamin D a day unless a doctor advises it.