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In the news: Green Tea & DNA Repair; Magnesium & Diabetes Risk

Green Tea May Boost DNA Repair

Collective evidence from over the past two decades suggests that green tea compounds are protective, and that drinking green tea supports good health. A small but interesting study conducted by Chinese researchers has shed some light on at least one way that green tea may work on the cellular level.

DNA, the spiral structure within cells that carries our genetic inheritance, can be damaged by environmental factors such as air pollution and tobacco smoke as well as by the free radicals generated during normal metabolism. The resulting damage, if not repaired, can lead to mutations and possibly disease. However Mother Nature has provided mechanisms that help fix DNA damage, and a number of enzymes are involved in this process.

In the new study, investigators tracked the activity of DNA repair enzymes in white blood cells (lympho-cytes) right after the study participants drank a cup of green tea, and after a week of drinking two cups daily. The control treatment was drinking water.

Compared to the control period, the researchers found that two enzymes were more active after drinking tea – one that’s important for fixing DNA damage from oxidation, and another that protects DNA from this kind of damage. Thirty percent less DNA damage was observed an hour and two hours after consuming a cup of tea, and in samples collected after the 7 days of tea consumption (1).

Boosting repair enzyme activity appears to be one way that green tea helps protect DNA. A next step might be to determine whether green tea has the same effects in other types of cells as it does in lymphocytes.

Magnesium May Help Stave Off Diabetes

Many population health studies have linked higher magnesium intakes with a reduced risk of developing type 2 diabetes. Now, the findings of a newly published study that followed over 2,500 middle-aged Americans for seven years, seems to affirm these observations.

Healthy people who consumed the most magnesium lowered their risk of developing metabolic impairments such as elevated glucose or circulating insulin levels that can lead to pre-diabetes and potentially to a diagnosis of type 2 diabetes (2).

Among participants who were already metabolically impaired, those with the highest intakes of this mineral were significantly less likely to develop type 2 than those consuming the least.

When looking at the combined groups (people with and without metabolic impairments at baseline), the highest consumption of magnesium cut the risk of developing diabetes in half.

Many magnesium-rich foods are rich in fiber too, and fiber also contributes to blood glucose control. When the researchers took fiber into account, fiber intake seemed to be partially responsible for the observations seen in the originally healthy group. However, it didn’t substantially affect results in the group with existing impaired metabolism. The researchers conclude that magnesium may be particularly beneficial in reducing the risk of diabetes among those who are at high risk.

These findings make good biologic sense since low magnesium levels can affect the ability of cells to respond to insulin – the hormone that enables cells to take up glucose from the blood stream. The findings are also important because large national surveys indicate that marginal magnesium deficiency may be relatively common in the US.

References

1. Ho CK, et al. Effects of single dose and regular intake of green tea (Camellia sinensis) on DNA damage, DNA repair, and heme oxygenase-1 expression in a randomized controlled human supplementation study. Mol Nutr Food Res June 2014 [Epub ahead of print].
2. Hruby A, et al. Higher magnesium intake reduces risk of impaired glucose and insulin metabolism and progression from prediabetes to diabetes in middle-aged Americans. Diabetes Care 37:419-27, 2014.