Bay Leaf, is it toxic or what?

One of the greatest myths I have faced through my whole life was having my mother shouting at me the great dangers associated to bay leaf. Yeah, exactly, that innocent cooking leaf that adds some good flavour to our tasty cuisine! Nevertheless, I was told by her that it was dangerous, but never really got to understand the reason why it was so intensively labeled as such a liability, to cook whit it, to have it as a "tool" for a touch of rural "glamour" to our food.

So, as a dedicated Toxicologist I had to undergo a fierce research towards the source of such theory. Is it  really true that bay leaf can be toxic? And if so, how toxic? And toxic to what biochemical level? 

For starters, I needed to fundament all my achievements and acquired information on proper scientific papers/websites rather than just Wikipedia cheap chat talk. Thus, I searched a few articles and found these pieces of amazing info concerning "Radical Scavenging Activity and Antioxidant Capacity of Bay Leaf Extracts", Elmastas et al., 2006 - an article issued on the Journal of Iranian Chemical Society; an article on "Isolation and identification of cytotoxic compounds from Bay leaf (Laurus nobilis)" from Fang et al., 2005; and a website regarding organoleptics. Going through these amazing articles I could easily understand how the biochemistry of the bay leaf easily fits one of the most "cliché" myths for toxic plants to be taken as extremely dangerous, being actually FALSE. In several articles I have researched I couldn't find a single mention to the strong toxicity of bay leaves. 

What happens with the bay leaves is that the presence of an excess of reactive oxygen species (ROS) (chemically-reactive molecules containing oxygen) that appear as a result of natural metabolic processes, as stated in a paragraph that I quote: "Exogenous chemical and endogenous metabolic processes in the human body or in food system might produce highly reactive free radicals, especially oxygen derived radicals, which are capable of oxidizing biomolecules, resulting in cell death tissue damage". This has been proven to be caused by certain flavonoids present in the bay leaf composition, that ultimately may end up causing apoptosis (programmed cell death), but can only a few leaves cause such damage? As it reads in one of the articles I checked "Oxidative damage plays a significantly pathological role in human disease. Cancer, emphysema, cirrhosis, arteriosclerosis, and arthritis have all been correlated with oxidative damage. Also, excessive generation of ROS, which is induced by various stimuli and exceeds the antioxidant capacity of the organism, leads to a variety of pathophysiological processes such as inflammation, diabetes, genotoxicity and cancer."


So, long story short, we have hexane and ethyl acetate present in Bay leaf that are responsible for potent biological activity causing apoptosis. The presence of sesquiterpene lactone  in bay leaf, a class of chemical found in many plants that can cause allergic reactions and toxicity IF OVERDOSED, particularly in grazing livestock, demonstrates that our cooking plant as lived under wrong premises of a potential toxicity that actually depends on overdosing from whoever ingests it. So, the next step is to get to know the LD50 (median lethal dose) of this plant. In Fang et al., 2005; the dried residues of three bay leaf extracts were bioassayed to reveal a LD50 of 10µg/ml, i.e., 10 milligrams per litre!!!!!!! And this value concerns the extract (already refined and purified to obtain only the interesting part, and not the whole leaf components).

So, where is this idea of bay leaf being really toxic is coming from? The misconception regarding bay leaf's toxicity comes from the fact that bay leaf plant is usually confused with Mountain Laurel (Kalmia Latifolia), related to bay leaf but different. It is actually Mountain Laurel (next image), as well as Cherry Laurel, that represent danger to humans and certain livestock and is just not sold anywhere as a spice, herb or food source. 

These are the actual guilty individuals in this story of toxicity of our flavouring leaf. The only problem you can get from bay leaf being used in your food is that even hard cooking will not help you digest it, so you should always avoid eating it, but that's it! To sum it up just retain this piece of information taken from a book's chapter 6 entitled "Bay Leaves", by Kumar et al.:

"Bay leaves and their essential oil do not appear to have any significant toxicity. However, sporadic reports have indicated that bay leaves may cause allergic contact dermatitis (Asakawa et al. 1974; Cheminat et al. 1984; Goncalo and Goncalo 1991) perhaps induced by one or more sesquiterpene lactone".

Bay leaves aren't only good for adding that speacial flavour to your food. The fact that they hold several sesquiterpene lactones reacting with vernolic acid make it responsible for reducing inflammantion and improving the celular structure of smooth muscle of blood vessels, which can help prevent atherosclerosis. Bay leaf is even  awesome on treating bronchial infections, and also used, if adequately applied to, as proper active medicinal tools on the treatment of gastrointestinal problems (flatulence, epigastric bloating, impaired digestion, eructation). In Turkey, popular medicine dictates that an infusion of bay leaves can help smooth hemorroids and  rheumatism, work fine as a diuretic and prevents urinary stones. 

To make it short, you would need a huge amount of bay leaves in your food to get an overdose or an allergic/toxic reaction from your organism. So keep on adding it adequately to your food as it may be eaten without toxic effect.


So here it is another revealed truth of an unmasked myth, once again in your 


The Toxicologist Today.