Sleep: the thinnest food evidence on this site

Put plainly, this is the thinnest food evidence on the site. Eight of 161 ingredients have any sleep result, and only two of those reach meta-analysis.

Ashwagandha has two meta-analyses pointing the same way. It is not, however, something you pick up with the groceries — it is closer to a medicinal herb, sold as capsules and powder.

Chamomile comes with a caveat. Sleep quality improved, but the result was not about insomnia. Someone who sleeps well sleeping slightly better is a different claim from insomnia improving.

Tart cherry has something other fruit does not: melatonin. Seven days of concentrated juice increased total sleep time and sleep efficiency. The study was small, though, and what was used was a concentrate rather than the fruit.

The lettuce sleep trials used extract capsules and seeds, not the leaf you put in a salad.

And two results went the other way. Casein before bed did not improve sleep, and the turkey-and-tryptophan story does not add up — the dose where an effect was reported is 1 g, and 100 g of turkey contains 0.252 g. It is short by a factor of nearly four. Holiday drowsiness is more plausibly about the size of the meal than the bird.

What to fix before food is clear.

The interventions with the largest effect on sleep are not foods. Keeping a constant wake time, cutting light before bed, and moving your last caffeine earlier all outweigh anything on this list. Caffeine's half-life is around five hours, so a three o'clock coffee is still with you at night.

• Ashwagandha is a supplement, not an ingredient. The guidance says to avoid it in pregnancy and breastfeeding and with thyroid or autoimmune conditions, and it can stack with sedating medication.
• Chamomile is in the daisy family. Take care if you are allergic to mugwort or ragweed, and interactions with warfarin have been reported.
• Melatonin supplements are classed as medicines in some countries and as supplements in others. Melatonin being present in tart cherry is not the same subject as taking a supplement.
• If you snore heavily or have been told you stop breathing in your sleep, consider sleep apnoea. That is not a food problem, and left alone it loads the heart and blood pressure.
• Trouble sleeping on three or more nights a week for over three months meets the threshold for insomnia. See a doctor.

This page is not for diagnosis or treatment.