Walnuts and jetlag

Author: Eoin O'Connell

When a popular magazine reported that walnuts can help to reduce the effects of jetlag, I could not resist looking into it.

The rationale goes like this:

- Melatonin levels in the body are elevated during sleep
- Introducing melatonin into the body can induce sleepiness
- Walnuts contain melatonin (3.5 ppm)

Therefore, eating walnuts can induce sleepiness at specific times of the day and help adjust to a new circadian rhythm.

The first statement above is true and easily verifiable. The second may be flawed because although there is a relationship between sleepiness and melatonin, we do not know the direction of causality or the required dosage. The third is true but because we do not know the required dosage, we do not know how many walnuts we need – this will prove crucial to the use of walnuts as jetlag medication.

Several researchers have experimented with exogenous melatonin, typically using measures of self-reported daytime fatigue, sleep quality, sleep latency (time to fall asleep) and sleep disturbances. The results from these studies are mixed but there is a slight bent towards the positive effects of melatonin – i.e. all things being equal, it probably won’t make your jetlag any worse but can make it better. There may however be side effects, increased ear/nose/throat irritation being the most likely.

In studies that have observed an amelioration of jetlag symptoms, the required dose of melatonin is between 0.5 and 5.0 mg (1 mg = 0.001 g). The recommendation usage is as follows: take 5mg of melatonin the day before and the day of travel at bedtime in the destination time zone. Then continue to take 5mg at bedtime for three days after arrival. See Beaumont et al. (2004), Piérard et al. (2001) and particularly Fitzpatrick (2006). This applies to flights crossing at least five time zones. Any fewer than five and jetlag will not be a big issue.

The tricky bit is still to figure out how many walnuts can give us the correct dose of melatonin. Korkmaz et al. (2011) very helpfully put together a table showing the melatonin content of a variety of foods. Figure 1 shows the amount of each food required to yield 0.5mg (the minimum required dose) of melatonin. The area of each triangle is scaled to the weight so it is a crude representation of piles of food.

St. John’s Wort, Sunflower Seeds and Turmeric (to name a few) contain more melatonin per gram than walnuts. One of the very best is Feverfew leaf (dried), you need just 71g of that to yield 0.5mg of melatonin. But considering dried Feverfew leaf mostly comes as a supplement in 500mg capsules, you will still need more than 140 capsules.

As for walnuts, you should eat between two and twenty times your body weight every day for five days to observe its effect on jetlag. Good luck.