What is bitter wood?

Bitter wood is the wood and bark of Quassia amara, a small tree of the Caribbean and northern South America. It is sold as pale chips, shavings or tinctures. The taste is intensely bitter, and that bitterness is the whole point of it.

In the Caribbean it is known as bwa amè in Haiti and Martinique, quassia in Jamaica, and cuasia amarga in the Dominican Republic. People took it to wake up the appetite, settle a slow stomach, and clear worms. It was also washed through the hair for head lice.

Here is the honest verdict. Human evidence is thin, and most of the claims rest on tradition alone. Head lice is the only use with even weak human data behind it.

Long and widespread use is not proof that a remedy works. It is also not proof that it is safe. Both of those need testing in people, and that testing has mostly not been done here.

How does bitter wood work?

The clearest part is the taste. Bitter compounds on the tongue set off a reflex that raises saliva and gut juices. This is a general effect of bitters, not something unique to this plant.

In people, that reflex is thought to lift appetite before a meal. Good trials to confirm it are lacking.

In test tubes and in animals, quassinoids from the wood slow or kill some worms, insects and malaria parasites. Whether a cup of steeped wood does the same inside the human gut has not been shown.

In male rats, quassia extracts lowered testosterone and sperm counts. The effect faded after the animals stopped. This has never been studied in men, so treat it as a warning rather than a fact.

What forms does bitter wood come in?

Most often you will meet it as raw wood chips or shavings.

Common forms: - chips or raspings, steeped in cool or warm water - alcohol tinctures and bitter elixirs - "bitter cups" turned from the wood, used to flavour water left standing in them - powdered wood in capsules - lotions and hair rinses applied to the scalp for lice - a flavouring in some bitters, aperitifs and tonic drinks

Strength is not standardised. Two bottles with the same name can differ a great deal.

Where it comes from:

Caribbean and Guianese healers used bitter wood for hundreds of years. It was taken for fever, poor appetite, stomach upset and worms.

The plant carries the name of Graman Quassi, an enslaved healer in Suriname. In the 1700s he was known for treating fevers with this wood. European traders carried it home, and it entered European pharmacy books as a standard bitter tonic.

It also had non-medical jobs. Brewers used it in place of hops, farmers used it against insects, and households used it as a fly poison and a hair wash for lice.

That record shows how trusted the plant was. It does not tell you that the old uses worked, and it is not a reason to dose yourself.

What does bitter wood help with?

• poor appetite: This is the oldest and most plausible use. Bitters taken before a meal raise saliva and gut juices in people. Whether this reliably makes you eat more has not been tested well for this plant.
• sluggish digestion and bloating: Tradition treated it as a stomach tonic after heavy food. There are no good human trials for bloating or indigestion. Some people find it helps; some find it irritates the stomach instead.
• intestinal worms: Caribbean use against worms is long-standing. Quassinoids harm parasites in test tubes and in animals. There are no proper human trials, and proven deworming medicines exist. Do not rely on bitter wood for a diagnosed infection.
• head lice: This is the use with the most human support, and the support is weak. Small, uncontrolled studies of quassia lotions reported that most people cleared their lice. There was no comparison group, so the result is not solid.
• fever and malaria (traditional use only): The tree's fame began with fever. Related quassinoids kill malaria parasites in the laboratory. That has not been shown to work in people at safe amounts. Malaria needs tested drugs and urgent medical care.

What are the side effects of bitter wood?

• nausea
• vomiting, especially at larger amounts
• stomach pain or cramps
• heartburn or stomach irritation
• a lingering bitter taste and dry mouth
• headache or dizziness, reported rarely
• skin or eye irritation from lotions and rinses

Good to know:

In the tiny amounts used to flavour drinks, problems are rare.

At herbal-remedy amounts, stomach upset is the common complaint. Vomiting is the usual sign that someone has taken too much.

Serious harm is not well documented, but the plant has never been tested properly for safety in people.

How much bitter wood should you take?

• Recommended daily: Labels on dried wood usually list a few tenths of a gram as a steeped drink. Tincture labels usually give a few drops up to a millilitre or two. Those figures are what packs carry. They are not advice for you, and they are not a target to reach. Large amounts cause vomiting and stomach pain. More bitterness does not mean more benefit.
• Best time of day: Bitters are traditionally taken shortly before a meal, because the taste reflex happens straight away. For other uses, timing has not been studied. For lice lotions, the time of day makes no difference.
• With or without food: For appetite, it is taken before food. Taking it on a very empty stomach can cause nausea in some people. If it upsets you, taking it with food is gentler. If it still upsets you, stop.
• Time to effect: The bitter taste effect is immediate, within a minute or two. Any change in appetite would show over a few days. For worms or digestion, no reliable timeline exists, because the effect itself is unproven. It may do nothing at all for you.
• How long to take it: It has been used as a short course, over days or a few weeks, rather than daily for months. There is no human safety data for long-term use. The animal findings on male hormones are a further reason not to keep taking it.