This small evergreen is one of several juniper species native to the northern hemisphere. It has the distinction, however, of being the principal flavoring for a commonly used alcoholic beverage, gin.
The aromatic “berries” (actually cones of this evergreen) have also been used in herbal medicine for at least three hundred years and perhaps longer.
Apothecaries once used gin as juniper berries are used to treat kidney ailments. More recently, golden raisins soaked in gin have become popular as a home remedy for arthritis (see page 233).
Juniper berries contain up to 2 percent volatile oil and 10 percent resin.
The oil contains more than one hundred compounds including monoterpenes such as alpha- and beta-pinene, myrcene, limonene, sabinene, and an alcohol, terpinene-4-ol, which appears to be responsible for the diuretic properties attributed to juniper berries.
The berries also contain as much as 30 percent invert sugar and small amounts of catechins, flavonoids, and leucoanthocyanidins.
The traditional use of juniper is as a diuretic and to treat conditions of the bladder or kidneys. Diuretic action of the essential oil is well established and attributed to terpinene-4-ol, which increases the filtration rate of the kidney.
Water-based extracts such as tea may not increase urination, although such an extract did lower blood pressure 27 percent in an experiment in rats. At high doses, however, juniper berries or their extract can be very irritating to the kidney.
It is a component of a number of herbal diuretic mixtures available in Europe.
Another traditional use of juniper berries or their extract is to pique the appetite or to aid digestion.
Extracts apparently increase peristalsis and intestinal tone.
Juniper berries were traditionally classified as “carminative,” meaning they can relieve flatulence. This use has not been carefully studied.
The Swedes traditionally used juniper berry extracts topically to treat wounds and inflamed joints.
Juniper tar has been used occasionally in combination with other plant tars to treat psoriasis of the scalp.
Test tube studies show that juniper berries can inhibit prostaglandin synthesis, which suggests that the traditional use for easing arthritis pain may have some scientific basis.
In addition, they apparently inhibit platelet-activating factor (PAF), which would discourage blood clots. This is not a traditional use for juniper berries in herbal medicine.
Juniper berry extract also has antioxidant activity.
Animal studies indicate that juniper berries lower blood sugar in experimentally induced diabetes. It has not been tested for this effect in humans.
The tea is made by pouring 2/3 cup boiling water over 2/3 teaspoon (2 g) of dried berries, steeping for ten minutes, and straining. This dose is repeated three or four times per day.
The best tea is made from berries rubbed through a sieve not more than one day prior to brewing.
For the tincture (1:5 in ethanol): 1 to 2 ml three times a day.
Juniper berries should be used for a maximum of four weeks except under medical supervision.
Juniper berries can be irritating to the kidneys. People with kidney problems should avoid them.
Pregnant women should not use this herb. Juniper berries might cause uterine contractions; they prevent implantation in female animals.
Diabetics who choose to try this herb should exercise caution and monitor blood sugar carefully.
Juniper berries lower blood sugar in animals and might result in hypoglycemia.
Dried juniper berries should be kept in a tightly closed metal or glass container (not plastic) and away from light. A desiccant similar to the ones found in many vitamin bottles should be included if possible.
Juniper berries or essential oil may be irritating to the kidneys. If the urine begins to smell of violets, the dose is too high or the herb has been used for too long, and kidney damage is a danger.
At high doses or over long periods of time, juniper berries can cause digestive distress, blood in the urine, or irritability and jitteriness. A single large dose can cause diarrhea.
As a topical treatment for psoriasis, juniper tar may increase the risk of skin cancer.
People sometimes develop allergies to juniper pollen or juniper berries. Such allergies are more prevalent in those who handle these plant materials.
If juniper berries do turn out to lower blood sugar, they would interact with diabetes medicines such as DiaBeta or Glucotrol and possibly with insulin. Close monitoring of blood sugar is advised.
Because of its effect on PAF, juniper berries may interact with anticoagulants such as Coumadin and possibly with other anticlotting drugs such as aspirin, Plavix, or Ticlid to increase the risk of bleeding. We are not aware of any cases, so this possibility remains hypothetical.
Ginkgo biloba also inhibits PAF, so it might be ill-advised to mix these two botanical medicines.