Researchers at the University of Guam found that the local noni trees grown in Akina soil in the southern part of the island have a higher amount of aluminum in their leaves.

The report, prepared by Drs. Thomas Marler and Jian Yang who collaborated on the study, was recently republished in UOG’s Western Pacific Tropical Research Center’s Impact Report.

Marler took leaf samples from trees on Guam, Rota, Tinian and Saipan between February and March 2012. Marler collected both old and new leaves from trees growing in different soils. He analyzed them with Yang and discovered aluminum concentrations in old leaves growing in Akina soil were much greater.

The noni trees growing in Guam’s southern acidic soil have elevated levels of aluminum, the impact report said. Inadvertent ingestion of excessive aluminum may occur if leaves from affected trees in the south are used for medicinal teas and the like, according to Yang.

Avoid ingestion

Yang warned consumers to be aware of noni trees with high aluminum content and to avoid ingesting old leaves.

The noni tree, also called lada on Guam, is most known for its medicinal properties. The noni fruit, which can be consumed as tea or juice, is known to heal a medley of illnesses.

Yang said the fruit of the tree contains high levels of antioxidants and vitamin C.

The leaves of the noni fruit are not used as much for medicine, according to James Stith, owner of JC noni, a local business that produces noni products including juice. Stith said he read Marler and Yang’s research.

Based on his reading of the research and other supporting material, Stith said, the elevated levels of aluminum in leaves are not sufficient to cause alarm.

“There are people who use the leaves for tea but we have never done that due to the superior nature of the nutrients found in the fruit,” Stith said. “It is a self- defeating practice; as you strip the trees of their leaves, they will stop growing.”

Stith said he believes the fruit is more potent than the leaves for healing purposes.

Yang, who also studied noni preparation in previous years, discovered how the fruit affects the levels of antioxidants and minerals in the noni juice.

Yang said some residents store the fruit in a jar outdoors and let it ferment, but that method proved to be the least conducive to preserving antioxidants and minerals for noni juice. He said people who drink noni juice to improve health and prevent illness should “freeze juice.”

The university used to teach this method during noni workshops, Yang said.

‘Freeze juicing’

According to a brochure on the subject, “freeze juicing” involves freezing and thawing the noni fruit. After about six to 12 hours of freezing, thaw the fruit and store the juice in the refrigerator. It should be consumed within two weeks.

The best types of fruit to use are the white-hard noni fruit, not the green ones, the brochure indicated.

According to the study, researchers sought out the potential for aluminum exposure resulting from consuming noni for health and medicinal purposes. The old leaves in trees grown in Akina soil contained four times as much aluminum than other trees’ leaves. When researchers infused 1 gram of these leaves in 240 milliliters of hot water, they measured about 0.83 milligrams per liter.

According to a 2003 paper from the World Health Organization, “It has been hypothesized that aluminum exposure is a risk factor for the development or acceleration of onset of Alzheimer disease in humans.”

The WHO concluded that drinking water with 0.1 milligrams per liter of aluminum did not cause Alzheimer’s in humans.

Conflicting studies

However, conflicting studies have reported different results when they studied cognitive dysfunction in the elderly related to levels of aluminum drinking water. One study of 800 male 80-year-olds showed no evidence of cognitive dysfunction when they consumed aluminum concentrations of up to 98 milligrams per liter.

A second study showed some relation of mental impairment when 250 elderly men were observed consuming water with aluminum levels of 85 milligrams per liter.

The WHO said such data is not sufficient enough to show aluminum can cause cognitive impairment in the elderly.