Are you a green tea lover? Read this carefully as the cup packed with anti-oxidants and other health benefits may adversely affect your fertility and development in case of frequent use, warn researchers.

In experiments over fruit flies, the team from University of California-Irvine discovered that excessive consumption adversely affected development and reproduction in fruit fly populations.

According to them, one should avoid high dose of green tea or any natural product as nutraceuticals such as green tea, while growing in popularity, are largely unregulated.

"While green tea could have health benefits at low doses, our study and others have shown that at high doses, it may have adverse effects," said Mahtab Jafari, associate professor of pharmaceutical sciences.

"Further work is needed to make any definite recommendations but we suggest that green tea should be consumed in moderation," she added.

For the study, Jafari and colleagues investigated the effects of green tea toxicity on the development and reproduction in fruit fly Drosophila melanogaster.

Embryos and larvae were subjected to various doses of green tea polyphenols.

Larvae exposed to 10 milligrams of green tea were slower to develop, were born smaller and exhibited a dramatic decline in the number of emerged offspring.

Ten milligrams of green tea made the flies more susceptible to starvation and heat stress but protected them against dehydration.

Female offspring showed decreased reproductive output and a 17 percent reduction in lifespan while males were unaffected, the study found.

Ten milligrams of green tea caused morphological abnormalities in reproductive organs such as testicular and ovarian atrophy.

Jafari believes that high doses of green tea may cause "too much" apoptosis or cell death.

Derived from the plant Camellia sinensis, green tea is popular worldwide for its purported brain and heart health and anti-cancer properties.

Jafari noted that in other tests with mice and dogs, green tea compounds in large amounts dramatically reduced body weight and, in mice, negatively affected embryo development.

"We are planning to measure total consumption and identify and quantify the metabolites of natural products in flies," Jafari pointed out, adding that these experiments will enable us to have a better understanding of toxic doses in humans.

The paper appeared in the Journal of Functional Foods.

Reducing the size of large food portions, packaging and tableware could help tackle obesity, a new Cambridge study has claimed.

Researchers have found the 'most conclusive evidence to date' that people consume more food or drinks from larger size portions or packages, and when using larger items of tableware.

The study at the University of Cambridge in UK found that eliminating larger portions completely could reduce daily energy intake consumed by 12 per cent to 16 per cent among adults in the UK, and by 22 per cent to 29 per cent among adults in US.

Researchers suggested steps like reducing food and drink serving sizes that contain high amounts of calories such as the standard single serving of confectionery, chips and cakes, and reducing availability of larger portion and package sizes.

They said that portion sizes should be limited at check outs, aisle ends and special displays. They also called for highlighting single portion sizes in packaging.

According to the researchers, implementation of portion size interventions will be easier in public sector organisations, such as schools, hospitals, military bases, and prisons, than in industries.

They said that reducing portion sizes may mean going back to sizes of portion and tableware similar to those in the 1950s, and changes may even involve reductions of over 50 per cent for some energy dense products.

This is far greater than the estimated 5 per cent reductions currently offered and negotiated with the food industry.

The study was published in The BMJ.

Exploring sexual identity, sexual attraction and sexual arousal in women, new research shows that heterosexual women have more diverse patterns of sexual response than previously reported.

In the first study, women watched short videos, and in the second study, women listened to stories about interacting sexually with a woman or a man.

Genital response was measured with a vaginal photoplethysmograph - a clear acrylic device that illuminates the capillary bed of the vaginal wall -- and participants also self-reported their sexual arousal.

In both studies, the lead researcher Meredith Chivers from the Sexuality and Gender Laboratory at Queen's University showed that only heterosexual women who were exclusively attracted to men showed similar genital responses to both female and male sexual stimuli.

Heterosexual women who also report some attraction to women, however, showed a different pattern of response - their genital responses were greater to female stimuli, similar to other sexually-diverse women.

"Both exclusively and predominantly androphilic women (women attracted to men) showed sexual response patterns that differed from their self-reported sexual attractions," Dr Chivers noted.

"Sexually-diverse women showed genital and self-reported arousal responses that were more similar to their self-reported sexual attractions," she noted.

As a whole, this research illustrates the complex relationship between sexual identity, sexual attraction, sexual arousal and genital responses to sexual stimuli.

Earlier research on women's sexual orientation and patterns of sexual response has previously focused on women's genital and subjective sexual arousal relative to their sexual identity, as heterosexual, bisexual or lesbian.

Among women, however, there is significant diversity among women in their sexual attractions to other women and men, regardless of sexual identity.

For example, a substantial minority of heterosexual women (20 per cent in some studies) also report some attraction to women.

"The new research provides a window of opportunity to understand how women's sexual response relates to her experience of sexual attraction and desire, addressing gaps in contemporary models of sexual response," concluded Dr Chivers in the journal PLOS ONE.

Researchers at Oregon State University (OSU) have discovered a new approach to preserving tissues and even organs for later use.

"This could be an important step toward the preservation of more complex tissues and structures," said Adam Higgins from OSU.

Ice-free cryopreservation has already found widespread use in simpler applications such as preserving semen, blood, embryos, plant seeds and some other biological applications.

But it is often constrained by the crystallisation that occurs when water freezes, which can damage or destroy tissues and cells, Higgins said.

To address this, researchers have used various types of cryoprotectants that help reduce cell damage during the freezing process -- among them is ethylene glycol, literally the same compound often used in automobile radiators to prevent freezing.

A problem, Higgins said, is that many of these cryoprotectants are toxic, and can damage or kill the very cells they are trying to protect from the forces of extreme cold.

In the new OSU research, the engineers developed a mathematical model to simulate the freezing process in the presence of cryoprotectants, and identified a way to minimise the damage.

They found that if cells are initially exposed to a low concentration of cryoprotectant and time is allowed for the cells to swell, then the sample can be vitrified after rapidly adding a high concentration of cryoprotectants.

The end result is much less overall toxicity, Higgins said.

The research showed that healthy cell survival following vitrification rose from about 10 percent with a conventional approach to more than 80 percent with the new optimised procedure.

The findings were published in the journal PLOS ONE.

Researchers have developed a new approach to rapidly expand the number of human liver cells in the laboratory without losing their unique metabolic function.

"This is the holy grail of liver research," said the study's lead author Yaakov Nahmias from Hebrew University of Jerusalem in Israel.

The research could help advance a variety of liver-related research and applications, from studying drug toxicity to creating bio-artificial liver support for patients awaiting transplantations.

"Our technology will enable thousands of laboratories to study fatty liver disease, viral hepatitis, drug toxicity and liver cancer at a fraction of the current cost," Nahmias noted.

Thus far, attempts to expand human hepatocytes - cells that comprise 85 percent of the liver - in the laboratory resulted in immortalised cancer cells with little metabolic function.

The scarce supply of human hepatocytes and this inability to expand them without losing function is a major bottleneck for scientific, clinical and pharmaceutical development.

The new method, described as the "upcyte process," allows expanding human hepatocytes, resulting in a quadrillion cells from each liver isolation, compared to only a billion cells that can be isolated from a healthy organ.

"The approach is revolutionary," said Joris Braspenning from Germany-based biotechnoloy company Upcyte Technologies.

"Its strength lies in our ability to generate liver cells from multiple donors, enabling the study of patient-to-patient variability and idiosyncratic toxicity," Braspenning said.

The study appeared in the journal Nature Biotechnology.