Can Asparagus Supplements Improve Sleep? Review Of 16 Studies Shows Early Promise

Asparagus is famous for one odd side effect, and better sleep isn’t it. Yet a new systematic review in the British Journal of Nutrition found that supplements made from the vegetable tended to improve sleep across 16 small studies, with early signs of eased anxiety and sharper attention too. There’s a catch: the trials were small, and the evidence is still early.

Researchers at the University of Reading in England, working with two scientists from a Japanese company called Amino Up, combed through 5,927 publications to gather the human evidence on what asparagus does inside the body. After weeding out animal studies, lab experiments, and papers that didn’t meet their standards, they were left with 14 papers describing 16 studies and 503 participants in total. Volunteers ranged from healthy adults around college age to taxi drivers, shift workers, and older adults with dementia, with average ages running from about 20 in one study to about 87 in another.

None of these studies served asparagus spears on a dinner plate. Participants took concentrated products, many built around a trademarked enzyme-treated asparagus stem extract called ETAS, along with asparagus powders and foods made with asparagus extract. Whether eating the vegetable itself does anything similar wasn’t tested. Funding also deserves a mention up front: Amino Up helped pay for the review as part of a PhD student’s research, and one of its employees on the author list co-wrote at least three of the 16 included studies.

Asparagus carries plant compounds, including antioxidants called polyphenols, that are known to fight inflammation. It also appears to raise levels of a protective protein called Heat Shock Protein 70, or HSP70, which helps cells cope with stress by preventing protein damage. Asparagus extract boosted HSP70 in lab-grown cells and, in one year-long trial, in older adults with early thinking problems. Separate mouse experiments found that HSP70 eased anxiety and memory trouble caused by sleep loss, but those animals received the protein directly, not asparagus. In the authors’ view, HSP70 is one of several possible routes by which asparagus might work.

Do asparagus supplements help people sleep better?

Sleep was the review’s most consistently positive area. Ten studies measured it, and many found better sleep quality, longer sleep, or people feeling more rested on waking, though not every measure improved in every study. People who already had sleep problems appeared to see the clearest gains.

In one week-long trial of 18 men, those taking asparagus extract had fewer dreams and nightmares and woke up closer to the time they wanted to. Another study paired asparagus with GABA, a calming chemical the brain makes naturally. Only the combination improved deep sleep as tracked by a wrist-worn fitness band; GABA by itself did not. In the review authors’ reading, that gap points to the asparagus extract as a likely contributor, though a single small trial of a combination product can’t show how much of the benefit came from each ingredient.

Better nights didn’t always mean sharper days. In some studies, daytime sleepiness stayed put even as night-time sleep improved. Daytime alertness, the authors point out, depends on much more than sleep quality, including diet, stress, and the body’s internal clock, and most of the trials never tracked what participants ate.

Can asparagus supplements sharpen thinking skills?

Seven studies tested memory, attention, and other thinking skills. A year-long trial of 30 older adults with mild cognitive impairment, an early stage of memory and thinking problems, produced the strongest results. Those who took a high daily dose of asparagus extract (1,000 milligrams) scored better than a placebo group on a standard test of overall mental sharpness, which covers memory, attention, and language, and on a test of reasoning and self-control.

A shorter, lower-dose trial in people with dementia, whose average age was about 87, found no meaningful edge over placebo on thinking tests after 12 weeks. It did ease agitation and low mood. Study authors believe the bigger dose taken for longer explains the difference, though the two trials also enrolled very different groups of people, which muddies the comparison.

In healthy younger adults, results were mixed. Some short trials found faster reaction times, better accuracy on an attention test, and less mental fatigue, while others found no change. Healthy people may simply have less room to improve, the authors note.

Asparagus extract, anxiety, and the stress hormone cortisol

Mood results leaned positive too. Anxiety scores fell in two studies, including one where volunteers took just a single dose, and depression-related scores improved in others. In the year-long trial, though, anxiety and depression eased only in people with milder impairment, not in those whose decline was further along. Sex may matter as well. Two similar trials tested the same asparagus food: the one that included women saw mental health scores improve, while an all-male version did not. More work is needed, the authors say, to tell whether men and women respond differently.

Several studies also tracked cortisol, the body’s main stress hormone, with mixed results. In the week-long nightmare trial, evening cortisol climbed in the placebo group but held steady in the asparagus group, which the authors read as a possible steadying effect on the body’s stress system. A 60-day study with no comparison group found drops in cortisol and norepinephrine, another stress-related chemical, after participants took large daily doses of asparagus powder. Yet a four-week trial in healthy young adults found no change in cortisol at all.

Are asparagus supplements worth trying yet?

For all the encouraging signs, the review is upfront about its weak spots. Individual studies were small, with roughly 10 to 60 participants each, and most lasted a month or less. Products ranged from powdered capsules to enzyme-treated extracts, which makes head-to-head comparisons hard. Three studies had no comparison group, making a placebo effect harder to rule out, and the volunteers skewed heavily male. Only two studies looked at people with cognitive decline, a gap the authors want closed, since that group often struggles with stress hormones, inflammation, and poor sleep, all areas asparagus appeared to influence.

Sixteen small studies leaning in the same direction, especially on sleep, is a signal worth following up. But short trials, mostly in men, testing a handful of concentrated products, some of them from researchers tied to the review’s corporate funder, can only raise the question, not settle it. Until larger, longer trials with standard doses come in, asparagus supplements remain a promising idea for better sleep, not a proven fix.

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Disclaimer: This article is for general information only and is not medical advice. Anyone thinking about starting a supplement, especially people who take medication or have a health condition, should talk with a doctor or pharmacist first.

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