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Nutrition News Bites: Green Tea, Calcium, and Shingles-Fighting Foods

Green Tea: Brain Beverage of Choice?

Drinking more than 2 cups of green tea daily could cut the risk of dementia by half, according to a new population-health study of elderly subjects (1). Researchers analyzed the consumption of beverages and foods for 1000 Japanese men and women with an average age of 74, and tested their cognitive function using a validated examination. Compared to people who drank less than 3 cups weekly, those drinking more than 2 cups daily had a 50% lower chance of having poor mental function.

The researchers believe that compounds in green tea called polyphenols, especially the polyphenol EGCG, could explain their observation. EGCG, which is able to enter brain tissue, is a strong antioxidant and may help prolong nerve cell survival. EGCG may also work by stimulating the growth of neurites, the hair-like projections on neurons that allow nerve cells to communicate with each other.

Big Problems with the WHI Calcium Findings

In addition to examining the health effects of a reduced fat diet (see March Staying Healthy), the Women's Health Initiative also studied the effects of calcium and vitamin D in healthy post-menopausal women. The WHI researchers just reported that "calcium with vitamin D supplementation resulted in a small but significant improvement in hip bone density, but did not significantly reduce hip fractures" (2). Many public health experts are worried that these headlines could cause women to give up on calcium supplements, thus undermining their bone strength.

An editorial that appeared along with the WHI publication in the New England Journal of Medicine points out that several aspects of the study may well have interfered with its ability to show a benefit in fracture rate. Two of the study's major stumbling blocks include:

• Compliance among the women was poor, with only 59% of the women adhering well to the supplement program. In fact, among those who actually took their calcium and D supplements regularly enough, the number of fractures was 29% lower than in the placebo group.
  
  
• The amount of vitamin D was very likely too low. The women received 1,000 mg of calcium daily along with 400 IU vitamin D. However, in recent years - and long after the WHI trial began - studies pointed to the need for a higher level of vitamin D. A comprehensive review of these studies found that 700-800 IU vitamin D daily is necessary to reduce the risk of hip fracture in older individuals, and concluded that an oral dose of 400 IU/day is not sufficient for fracture prevention in older people (3).

Vitamin D and calcium aren't the only things that can reduce fracture risk: regularly weight-bearing exercise, smoking cessation and adequate protein intake are also risk-reducing. But sufficient D and calcium are still important for women before and after menopause.

Fruits, Veggies Cut the Risk for Shingles

British researchers examined the relationship between vitamin and mineral intake, as well as fruit and veggie consumption and the risk of getting shingles. The virus that causes shingles (herpes zoster) is found in everyone who has had chicken pox, a disease that has affected more than 90% of most populations. If the immune system is weakened, the dormant virus can reactivate. Older people are more at risk for shingles.

The investigators compared the intake of 7 nutrients that are necessary for immune function in 243 people who had shingles with intake of the nutrients in healthy aged-matched controls (4). They found that people with limited intake of these nutrients - vitamins A, B6, C, E, folic acid, iron and zinc - had a 5-fold increased risk of shingles. Eating less than a piece of fruit daily was also linked to a 3-fold increase in risk. Many of these 'immune' nutrients are plentiful in fruits and vegetables.

References

1. Kuriyama S et al. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1. .Am J Clinical Nutrition 83:355-61, 2006.
2. Jackson RD et al. Calcium plus vitamin D supplementation and the risk of fractures. N Eng J Med 354:669-83, 2006.
3. Heike A. Fracture prevention with vitamin D Supplementation:. a meta-analysis of randomized controlled trials. JAMA 293:2257- 2264, 2005.
4. Thomas SL et al. Micronutrient intake and the risk of Herpes zoster: a case control study. Inter J of Epidemiology (Epub online, 2005)