Jerusalem Post

ByDORON KUPERSTEIN

Not every vitamin is suitable for nighttime: B12, calcium, and multivitamins may harm sleep, while magnesium, vitamin C, and omega 3 actually contribute to relaxation and deeper sleep.

Taking vitamins and supplements has become part of the daily routine for many, and sometimes the simplest way to remember to take them is before bedtime. However, this habit may actually impair sleep and lead to tiredness the next day. Nutrition and health experts explain which vitamins and supplements are best not taken at night, and on the other hand – which ones may contribute to better and continuous sleep.
Vitamins and supplements to avoid before bedtime
Vitamin B12
B vitamins – and especially B12 – are involved in energy production processes and nervous system function. Clinical dietitian Hannah Wholesome explains: “Vitamin B12 is best taken in the morning, to make use of its contribution to alertness and daily activity.”

Studies have shown that both deficiency and excess of B12 may cause sleep problems and even insomnia. Therefore, it is important to maintain proper daily intake: 2.4 mcg for adults, 2.6 mcg for pregnant women, and 2.8 mcg for breastfeeding women.

Calcium
Although calcium is essential for bone and muscle health, taking it at night may impair sleep, since it competes with magnesium for absorption. Magnesium is considered an important mineral for relaxation and good sleep, so calcium close to bedtime may actually interfere.

The recommended amount is 1000 mg per day for adults (1200 mg above age 51). It is better to obtain calcium from food – dairy products, tahini, almonds, and green vegetables – rather than from a supplement before bedtime.
Multivitamins
Most multivitamin supplements also include B12 and calcium, and sometimes also fat-soluble vitamins that are absorbed better with a fat-rich meal. Therefore, it is best to take a multivitamin in the morning or at midday, not as part of the nighttime routine.

In addition, not everyone needs a multivitamin – it is mainly recommended for pregnant women, people with absorption problems, or older adults with reduced appetite.
Vitamins and supplements that may improve sleep quality
Magnesium
The mineral considered “a good friend of sleep.” Studies have shown that taking magnesium threonate about two hours before bedtime improved sleep quality, especially the deep sleep stage.
It is recommended to take 200–400 mg in the evening, in the form of magnesium glycinate or citrate, which are well absorbed and generally well tolerated. Dietitians also recommend preparing a “sleep mocktail” with magnesium powder, water, and a small amount of tart cherry juice – a combination that contributes to relaxation.
Vitamin C
A 2024 study found that high levels of vitamin C in the blood are linked to better sleep and fewer sleep disturbances. Recommended daily dosage: 75 mg for women and 90 mg for men (up to 120 mg for breastfeeding women).
Iron
People with iron deficiency may suffer from sleep disturbances. Taking iron can improve sleep quality and also help in conditions such as restless legs syndrome. Recommendations: 8 mg per day for men, 18 mg for women, and 27 mg for pregnant women.
Omega 3 fatty acids
Omega 3 supplements have been linked to higher sleep efficiency – meaning the ability to spend more time sleeping out of the time spent in bed. The mechanism of influence is likely related to serotonin secretion, which affects sleep cycles. Recommended daily dosage: 1.1–1.6 grams for adults, with higher amounts for pregnant or breastfeeding women.
In conclusion
The pursuit of good sleep depends not only on the number of hours but also on quality. To prevent harm to sleep, it is advisable to avoid taking B12, calcium, or multivitamins before bedtime. Instead, supplements such as magnesium, vitamin C, iron, and omega 3 may contribute to relaxation and deeper sleep.
Of course, every supplement should be taken according to personal needs and in consultation with a doctor or clinical dietitian.