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Secret Ingredients of Cranberry Juice

Urinary tract infection is one of the most common diseases among women.  About one-quarter of the women in the U.S. are estimated to have had at least one urinary tract infection in their lifetime.

For years, cranberry juice has been used for the prevention and treatment of urinary tract infections.  In 1994, a Harvard study provided the clinical evidence to support its effectiveness.

E. coli are the primary bacteria responsible for urinary tract infections.  Recent studies indicate that something in cranberry juice prevents E. coli bacteria from attaching to the epithelial cells in the urinary tract, thus preventing bacterial colonization and subsequent infection.   So what are those ingredients  in cranberry juice that prevent urinary tract infections?

Researchers at Rutgers University, New Jersey and their colleagues in New Zealand, recently isolated the specific compounds responsible for cranberries' E. coli-fighting effect.

They isolated six compounds from cranberry extract and determined their structures spectroscopically. Then they demonstrated that only three trimeric procyanidins, consisting of three “epicatechin” compounds, inhibit E.Coli from adhering to cell surfaces in laboratory tests. They also demonstrated that the other three isolated compounds, an epicatechin and its two dimers, showed little or no activity.

The researchers concluded that these three compounds, trimeric procyanidins in cranberry juice, contribute, at least in part, to the observed health benefits.

Reference; Foo Y L., et al., A-Type Proanthocyanidin Trimers from Cranberry that Inhibit Adherence of Uropathogenic P-Fimbriated Escherichia coli, J. Nat. Pod. September, 2000, Vol. 63, p1225-1228.

Carrots and Tomatoes Can Reduce Lung Cancer Risk

Carotenoids are a group of phytochemicals that have strong anti-oxidant properties. Because of this property, carotenoids may reduce lung cancer risk.  However, relatively few studies have examined the relation between intakes of individual carotenoids (a-carotene, b-carotene, lutein, lycopene, and b-cryptoxanthin) and lung cancer risk.

Now a research team led by Dr. Dominique at the Harvard School of Public Health reports that several carotenoids, such as a-carotene and lycopene, reduce lung cancer risk.  Using a questionnaire, earlier researchers had obtained information about the health and diet of 46,924 U.S. professional men 40-75 years of age in 1986, as well as 77,283 female nurses 30-55 years of age in 1976.  Researchers continued to obtain the same information every 2 years.  This was done for 10 years for the men and 12 years for the nurses. During the follow-up periods, 275 men and 519 women were diagnosed with lung cancer.

Using this data, the Dominique team performed a statistical analysis that indicated the following:

1.   a-carotene and lycopene significantly reduced lung cancer risk.

2.   Other carotenoids were not significant in reducing lung cancer risk.

3.   Increased a-carotene intakes lowered lung cancer risk by 63% among non-smokers.

4.   Increased lycopene intake significantly lowered the lung cancer risk of all participants, including smokers.

Carrots contain a large amount of a-carotene; tomato products, such as tomato juice and ketchup, contain a great deal of lycopene. Therefore, eating carrots and tomato products may be recommended for reducing the risk of lung cancer.

However, because less than 10% of all lung cancers occur in non-smokers, quitting smoking is still a far better way to reduce lung cancer risk.

Note: Phytochemicals are plant chemicals that contribute to the bright and vivid colors found in fruits and vegetables.

Reference: Dominique S M et al., Intake of specific carotenoids and risk of  lung cancer in 2 prospective U.S. cohorts, Am J Clin Nutr, October 2000, Vol. 72, pp990-7.

Vegetarians Have Less Heart Disease

Despite widespread acceptance that vegetarians have lower mortality from ischemic heart disease (IHD) than meat eaters, the research on the relationship between vegetarianism and heart disease has been surprisingly sparse. Recently, however, Hong Kong scientists reported that older Chinese women who are vegetarians have a lower risk of ischemic heart disease when compared with non-vegetarians.

In their study, 90 vegetarian Chinese women over 70 years of age were screened for ischemic heart disease by electrocardiogram (ECG) and a cardiovascular questionnaire.  These women were compared with 90 non-vegetarian women of similar age. After a twelve hour fasting period, blood was taken from all participants and tested for serum cholesterol and triglyceride levels.

The dietary habits of these women were assessed by a food frequency questionnaire. It was found that the vegetarians, for religious reasons (Taoism and Buddhism), did not consume any meat or fish for 41.1 years on average. Unlike vegetarians in Western countries, however, they did not exercise very much.

After adjustment for confounding factors, such as diabetes, smoking, alcohol consumption etc., researchers found that the vegetarians had much lower serum cholesterol levels and a lower risk of ischemic heart disease when compared with non-vegetarians.

This could be attributed to their low fat intake, but researchers think this is also due to factors such as the presence of antioxidants (vitamin E, beta carotene, vitamin C), n-3 and n-6 polyunsaturated fatty acids, and arginine in vegetables and fruits.

Although it is not necessary to completely eliminate red meat from the average American daily diet, these conclusions suggest a plant-centered diet should be strongly encouraged.

Reference: Kwok T. et al., Vegetarianism and Ischemic Heart Disease in Older Chinese Women, the American College of Nutrition, October 2000, Vol. 19, No. 5, pp622-7.

Tofu Lowers the Risk of Heart Disease

Many scientists have noted the lower incidence of heart disease in Asians when compared with the Western population. Scientists suggested that the higher consumption of soybean products by Asians may in part explain the above observation.

Researchers at Hong Kong University reported that higher soy intake lowers total plasma cholesterol level and LDL (low density lipoprotein) cholesterol, thereby reducing the risk of heart disease. In a recent study, urinary excretion of isoflavones, a reflection of dietary soy intake, was observed to be 100 to 1000 times higher in Japanese than in Caucasian women, with correspondingly lower levels of cholesterol for the soy eaters. 

A total of 500 men and women, aged 24 to 74 years, completed the above dietary intake study.  The dietary assessment was based on a semi-quantitative food frequency questionnaire consisting of 253 food items, including 10 soy items such as soybeans, soft tofu, firm tofu, deep fried tofu, bean curd skin, and soy milk. Subjects were also given a physical examination and blood and urine tests.

It was found that most of the participants had consumed soy products at least once or twice during the previous week and that about 80% of the soy protein or isoflavones were obtained from different forms of tofu, along with an additional 9% from soy milk.

The most important finding was that the higher the intake of soy products, the less concentration of total plasma cholesterol and LDL cholesterol. But interestingly, this association was not observed among women over 50 years of age. Researchers speculated that in order to get the same benefits, older women are required to eat more soy products.

Researchers proposed that the cholesterol-lowering effect of soy protein is due to the stimulation of bile acid excretion from cholesterol in the blood stream, resulting in the reduction of total plasma cholesterol.

Because it is known that a 1% reduction of cholesterol is translated into a 2% reduction of heart disease, it is probably a good idea to eat more soy items.

If you don't like tofu or soy milk, you can try roasted soy nuts, soy burgers, soy sprouts, soy powder in your favorite smoothie, or soy flour in recipes.

Note: Isoflavone is a type of phytochemical found in soybeans. Isoflavones may be classified as phytoestrogens, meaning that their chemical structures are similar to estrogen. Phytoestrogens  are plant-derived substances that bind to estrogen receptors.

Reference: Ho C.S. et al., Intake of Soy Products Is Associated with Better Plasma Lipi Profiles in the Hong Kong Chinese Population, J. Nutr. October 2000,  Vol. 130., pp2590-3.

Hepatitis C is Linked to Diabetes

About 2.7 million Americans have chronic hepatitis C virus (HCV) infection. HCV can cause severe chronic fatigue and eventually lead to cirrhosis of the liver and liver cancer. People with severely damaged livers must have a liver transplant or they will die. Past studies suggested that HCV patients are 2-5 times more likely to develop type 2 diabetes than people without HCV infection--but is this true?

Most of the previous studies did not consider possibly confounding factors such as body mass index, age, poverty level, education level, or history of drug and alcohol use. Moreover, most HCV patients in previous studies had severe forms of the disease and, thus, diabetes was more likely to occur due to the failure of carbohydrate metabolism and glucose homeostasis in the liver. So the real question is, “Are persons with HCV infection with less severe liver disease likely to develop diabetes?”

In a new study conducted by researchers at Johns Hopkins Medical Institutions, researchers examined the prevalence of type 2 diabetes among persons with HCV infection, using data from persons 20 years and older who participated in the third National Health and Nutrition survey, 1988-1994.

Of the 9,841 subjects, 1,242 (8.4%) had type 2 diabetes, 19 (0.4%) had type 1 diabetes, and 230 (2.14%) had HCV infection. One conclusion was that type 2 diabetes occurs more often in persons with HCV infections who are over 40 years of age.

After adjustment for the confounders mentioned earlier, researchers’ careful analysis also indicated the following:

1.   Persons older than 40 years of age with HCV infection were more than 3 times more likely to have type 2 diabetes than those without HCV infection, regardless of the severity of disease.

2.   No increase in the prevalence of type 2 diabetes was found among persons with hepatitis B infection.

3.   The prevalence of type 1 diabetes among persons with HCV infection did not increase.

It is not surprising that those younger than 40 years of age with HCV infection did not have increased occurrence of type 2 diabetes, because persons in this age group without HCV infection rarely have type 2 diabetes.

It seems that HCV infection causes type 2 diabetes through progressive liver damage. Further research is needed, however, to explain the underlying biological mechanism.

Reference: Mehta H S et al., Prevalence of Type 2 Diabetes Mellitus among Persons with Hepatitis C Virus Infection in the United States, Ann Intern Med, October 17, 2000, Vol. 1333,  pp592-9.

Benefits of Water Fluoridation

Since 1950 the number of individuals drinking fluoridated water has steadily increased because of the strong belief that fluoridated water prevents dental caries (tooth decay, or cavities).  It is estimated that worldwide today at least 300 million people drink fluoridated water, including 5.5 million in England and 144 million in the U.S.  Is the fluoridated water really safe to drink?

Researchers at the University of York reported that fluoridated water does indeed reduce the incidence of caries, but with the increased prevalence of dental fluorosis (mottled teeth). They examined 214 previously published studies (up to February 2000) through an electronic database and the World Wide Web.

It was found that water fluoridation was associated with an increased proportion of children without caries and a reduction in the number of teeth affected by caries. But researchers also found a dose-dependent increase of fluorosis. Most importantly, however, no association was found between water flouridation and any other negative effect in terms of cancer, Down’s syndrome, mortality, senile dementia, goiter or IQ.

In a different study, Dr. Kathy Phipps at the Oregon Health Science University and her colleagues specifically looked at the association between fluoridated water and the risk of bone fracture, because previous ecological studies suggested that exposure to fluoridated water increases the risk of bone fracture.

These researchers think that the previous ecological studies had a major design flaw because they did not control confounding variables at individual levels, such as physical activity, history of fall, history of medical conditions, weight, age and smoking.

The Phipps group compared bone mineral density and incident fracture rates for 2,563 white women aged over 65 years with no exposure to fluoridation and 3,218 white women of similar age with continuous exposure for at least 20 years. After adjustment for confounding factors, they concluded that women with continuous exposure to fluoridated water had higher bone mineral density at the lumbar spine and hip and a slightly reduced risk of hip and vertebral fractures.

If long-term exposure to fluoridation does reduce the risk of hip fracture, especially among elderly women, community water fluoridation may be one of the most cost effective methods for reducing the incidence of fractures related to osteoporosis. Moreover, fluoridated water is good for preventing the development of cavities as well.

Note.  "Mottled teeth" refers to marking of the teeth with  blotches of a different color.  

Reference: McDonagh M.S., et al., Systematic review of water fluoridation, BMJ, October 7, 2000, Vol 321, pp855-9.

Reference: Phipps R. K., et al., Community water fluoridation, bone mineral density, and fracture: prospective study of effects in older women, BMJ, October 7, 2000, Vol 321, pp860-4.

Why are Plant Leaves Green ?

If someone asks you why most plant leaves are green, what would you say?  According to new research by a University of Wyoming team, the answer lies not only in what meets the eye, but also in what is inside the leaf. 

Our eyes can only detect so called visible light at wavelengths between 400 nanometers (violet) and 730 nanometers (deep red). Sunlight is actually a mixture of many different wavelengths (do you remember 7 colors in the rainbow?). So when sunlight impinges on a bunny and if sunlight of all wavelengths is reflected (not absorbed), it looks white. Likewise if a red wavelength is reflected off an apple, the apple looks red.

Plant cells in leaves contain green pigments called “chlorophylls” which absorb light and drive the process of photosynthesis, producing carbohydrates (sugars) by using carbon dioxide and water. Chlorophylls (a and b) usually do not absorb green light as much as red and blue light. Therefore, when sunlight impinges on leaves, green light is reflected and they look green.

The above explanation is an optical reason but it gives a false impression that green is not important for photosynthesis.

A research team led by Dr. John Nishio at the University Wyoming examined the role of green light in carbon fixation (photosynthesis) within spinach leaves.  The Nishio team found that not all green light is reflected off the surface of leaves, but some is absorbed and drives carbon fixation deep within leaves.  Blue and red light, on the other hand, drives photosynthesis near the top surface of the leaf.

Researchers found that within the leaf there is a strong correlation between the gradients of green light, carbon fixation and Rubisco, an important enzyme involved in the initial step of photosynthesis.  This finding demonstrates the important involvement of green light in photosynthesis.

Higher plants have evolved to allow the use of green light from the top of the leaf surface to the bottom to make best use of green pigments, namely chlorophylls (a and b), for photosynthesis. That is a physiological reason for why plant leaves are green.

If higher plants had evolved to reflect different colors on their leaf surfaces, such as blue or red, those pigments would absorb green light mainly at the top surface of the leaves and would not allow green light to transmit deeper in the leaf for more photosynthesis to take place. That’s why plants use green pigments which absorb green light only slightly at the top surface (reflecting it back to our eyes as green) and allowing green light to travel deeper inside the leaf for more photosynthesis, Dr. Nishio explained.

Reference;Nishio N. J., Why are higher plants green ? Evolution of the higher plant photosynthetic pigment complement, Plant, Cell and Environment, June 2000, Vol. 23, pp539-548.

Bt Rice -- Rice with Built-in Insect Resistance

Due to advances in plant biotechnology, Bt crops of soybean, cotton, maize, and potato have been developed and commercialized. Bt crops are biologically engineered to resist certain insect pests.  Now, Bt rice has made its debut.

  production In Asia has undergone significant changes in recent years.  First, hybrid rice became a commercial success with 20% higher yields than inbred rice. But this success came with a price--hybrid rice is vulnerable to insect pests, especially stem borers. Chemical spray against stem borers is not preferred because it is infective and pollutes both land and water.

Bacillus thuringiensis (Bt) is a bacterium used for more than 50 years as a biological insecticide and an alternative to chemical sprays.  d-endotoxin, produced by Bt, binds to the insect midgut (digestive tract) and damages its cell membrane, causing death.  Bt insecticide activity is highly specific and d-endotoxin is not toxic to birds or humans. However, biological insecticide has some limitations because it has to be applied at the correct time--before insect larvae penetrate the stem.

With these problems in mind, researchers in China developed a high yield Bt rice through biological engineering, with Bt genes bred into the crop. They developed a transgenic rice line, Minghui 63 and its derived hybrid, Shanyou 63 by introducing Bt genes (CryIA(b) and CryIA(c)) for d-endotoxin.

Field evaluation of this Bt rice showed strong resistance against extremely high, repeated infestations of two important lepidoptern pests, the yellow stem borer and leaffolder, with higher yields than non-Bt commercial hybrid rice.

Because China and tropical Asian countries have more serious insect problems than other regions and also need to feed an expanding population, Bt commercial hybrid rice can be a very important and useful innovation for this part of the world.