Luteolin Simply Explained

1. What It Is About

Luteolin belongs to the group of plant compounds that protect plants and give them colour. It is found in parsley, celery, thyme, kale, artichokes and chamomile. In plants, it helps defend against stress and pathogens. In research, it is classified as a polyphenol, a large group of plant compounds.

Luteolin is studied both as a pure substance and as part of plant extracts. It is usually taken orally, rarely applied to the skin or in the mouth. The body absorbs it poorly, so preparations with particularly finely ground particles are used.

For understanding the studies, one thing is important: in almost all human studies, luteolin was not given alone but together with another substance, palmitoylethanolamide, abbreviated as PEA. PEA is a fat-like substance produced by the body. This combination is referred to as PEA-LUT in the studies. Controlled studies are those in which one group receives the combination and another receives a placebo for comparison. Whether luteolin alone has a similar effect has not been tested in controlled human studies.

2. What Studies Show

The best-studied area is olfactory disorders following COVID-19 infection. In a study with 185 people who still had poor smell more than six months after infection, one group took the luteolin-PEA combination and performed an olfactory training involving regular smelling of scents. The other group only did the olfactory training and received a placebo. After 90 days, the first group performed significantly better in an olfactory test 3.

Two further studies with 202 participants divided the subjects into four groups with different treatments. Only the combination of the mixture and olfactory training was better than placebo at the end. The mixture without olfactory training showed no clear advantage 6 4. This finding is supported by the controlled studies, which point in the same direction.

In a study with 69 people with olfactory disorders and concentration problems after COVID-19, both smell and thinking improved under the combination. However, there was no placebo group for the thinking part, so the results are indications but not yet confirmed 5.

In 60 people with a recent stroke, the combination was given in addition to standard treatment. After 90 days, they showed better values in tests of nerve function and daily living skills than the comparison group 1.

In a study with 60 people with gum disease (periodontitis), a plant tincture containing a sugar-bound form of luteolin was used in addition to standard dental treatment. After three months, two specific bacterial species were found less frequently, while a third remained unchanged 2.

For this page, a total of 248 studies were evaluated, including 8 controlled human studies, 25 observational human studies, 27 reviews, 16 animal studies and 59 cell culture studies.

3. What Remains Unclear

The biggest open question is: how much of the observed effect comes from luteolin itself? In controlled human studies, luteolin was almost always given together with PEA. Groups receiving luteolin alone did not exist.

Little is also known about long-term effects. The studies usually lasted only a few months, and many were conducted at a single site. Whether the observed effects persist over years and whether the combination remains well tolerated in the long term is therefore unclear.

How the combination works in the body has so far mainly been described in cell and animal studies. Measurements in blood or brain imaging to confirm this in humans are still lacking. It also remains to be clarified whether people with mild or severe olfactory disorders respond differently.

4. What This Means in Everyday Life

Luteolin is found in everyday foods such as parsley, thyme and chamomile. However, the studies did not investigate these foods but precisely defined preparations, sometimes with particularly small particles and always in fixed combination with PEA.

A positive result with such a preparation does not therefore imply that a food or an over-the-counter product has the same effect. When reading reports about luteolin, it is worth asking whether luteolin alone or the combination with PEA is being discussed. Most often, it is the combination.

The next step in research would be a controlled study directly comparing luteolin, PEA and both together. Only then can it be determined which part of the observed effect is due to luteolin and which to PEA.

All details with study numbers and sources: detailed page on luteolin. For children: Luteolin for children.