What Is the Magic Ingredient in TikTok's 'Sleepy Girl Mocktail'?

A "sleepy girl mocktail" has gone viral on TikTok, with supporters claiming it helps them fall asleep — and stay asleep.

"I sleep like an absolute baby when I drink this," said TikTok creator Maddison__Lynn, whose video had 3.8 million views. And TikToker Taaylorvictoriaa shared a video with her mom, who said the drink gave her "the best sleep I've had in I don't know how long."

Their video had more than 4.4 million views.

There are variations on the drink, but the consistent ingredients are seltzer (Poppi's raspberry rose is often used), magnesium, and tart cherry juice.

But while tart cherries contain a small amount of melatonin, what's really helping people relax is the magnesium.

Magnesium can help with sleep as well as anxiety, which also impacts nightly rest.

"It's not a myth. Magnesium does help with anxiety and mood and it also helps with sleep, which as we know, getting good quality sleep also helps with anxiety and mood,” Kristina Freshour, a registered dietician at the Katz Institute for Women's Health, tells PEOPLE.

The mocktail — and magnesium supplements — may work because they're helping to remedy a simple case of magnesium deficiency.

“There are studies that show that people that struggle with anxiety or even depression tend to have lower levels of magnesium and when supplemented, the anxiety does improve,” Kristina Freshour, a registered dietician at the Katz Institute for Women's Health, tells PEOPLE.

But there are different types of magnesium on the market, Freshour says.

“The one that you'll see most often on the shelf is magnesium oxide and this is actually not well absorbed at all. So it's probably not a good type of magnesium to take if you are taking it for things like sleep and anxiety.”

The type of magnesium to find for a good night's rest, Freshour tells PEOPLE, is magnesium glycinate.

“For sleep or anxiety, or even muscle cramps, magnesium glycinate is the best one to take."

But you can take too much of the supplement, Freshour warns. “There there is such thing as magnesium toxicity,” she tells PEOPLE. “If you have too much magnesium, the kidneys usually help compensate by excreting, but sometimes if it's too much, your kidneys cannot keep up and it can result in diarrhea.”

Other symptoms of magnesium toxicity, she says, include dizziness, nausea, and retention of urine.

But you can also consume magnesium naturally.

“The top five top food sources are pumpkin seeds, chia seeds, almonds, dark leafy greens like cooked spinach, and cashews," Freshour notes, adding that the standard American diet is low in magnesium.

And Freshour points out that cooked spinach is a better source of magnesium then, say, spinach salad. 

“It's more available for absorption because you are cooking down some of those anti nutrients in the raw vegetables. So, they are more bioavailable when they are cooked.”

But don’t ditch your salads. “Some nutrients will be higher in the raw vegetables. Some will be higher in cooked vegetables. So, just making sure you get a variety is the best bet for everyone."