Thursday, November 28, 2024

 WOMEN'S HEALTH

Should postmenopausal women eat soy? University of Toronto researchers dispel myth about soy and cancer




University of Toronto
Chiavaroli_Viscardi 

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University of Toronto professor Laura Chiavaroli (left) and PhD student Gabrielle Viscardi

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Credit: University of Toronto




A University of Toronto study is providing reassuring evidence about the consumption of soy foods in women* who are postmenopausal.

The analysis of 40 randomized controlled trials in over 3,000 participants found that estrogen-like compounds in soy had no effect on key markers of estrogen-related cancers, supporting its safety as both a food and potential therapy.

Several health advocacy groups including the Canadian Cardiovascular Society already recommend soy foods as part of a healthy diet. They are a high quality and complete source of protein and are recognized by several national governmental health agencies — including Health Canada and the US Food and Drug Administration — as effective in reducing the risk of heart disease. Soy foods have also been shown to alleviate hot flashes associated with menopause, which affect many women and impact their quality of life.

“The risk of cardiovascular disease increases substantially as women go through menopause, so soy can offer dual benefits during this particular phase of life,” says Laura Chiavaroli, the study’s senior author and an assistant professor of nutritional sciences at U of T’s Temerty Faculty of Medicine

Yet she notes that many people are hesitant to eat soy foods because they contain estrogen-like compounds called isoflavones, which are naturally found in plants and have a similar structure to the hormone estrogen. In animal studies, large doses of isoflavones have been linked to a higher risk of cancer.

“Something we hear very often is that people have a lot of concern about consuming soy because there are so many conflicting messages out there,” says Gabrielle Viscardi, a second-year PhD student in the department of nutritional sciences and the study’s lead author. 

In their systematic review and meta-analysis, published in Advances in Nutrition, the researchers gathered results from trials that compared the effects of soy isoflavones on four different biological outcomes related to risk for endometrial and other female-related cancers. Those outcomes included the thickness of the uterus lining, the vaginal maturation index — a measure of estrogen status within the vaginal environment — and levels of circulating estrogen and follicle-stimulating hormone. 

The trials followed postmenopausal women from around the world who had consumed either soy isoflavones or a non-isoflavone control for at least three months. 

After assessing the risk of bias and quality of the evidence, the researchers concluded that consumption of soy isoflavones did not affect these four estrogen-related markers. Their findings support the idea that soy isoflavones behave differently from human estrogen, particularly when it comes to cancers that depend on estrogen to develop.

“We have estrogen receptors throughout our bodies but, contrary to the hormone estrogen, isoflavones from soy don’t bind to all the estrogen receptors equally,” says Viscardi, who is also a registered dietitian.

“That’s why we see a beneficial effect on the cardiovascular system and no effect on the female reproductive system.”

This difference in biological activity explains why soy isoflavones have been considered as a possible alternative to hormone replacement therapy (HRT), which is used to treat menopause symptoms by replacing the estrogen that the body stops producing during this period. 

Chiavaroli, who is also an affiliate scientist at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital, Unity Health Toronto, notes that some people do not want to take HRTs and are seeking alternative options.

Further, HRTs may also not be a good option for people at an increased risk of estrogen-sensitive cancers like breast cancer, as well as those with a history of heart disease and stroke. For these individuals, consuming soy foods as part of a balanced diet could help manage their menopausal symptoms while also reducing their risk for cardiovascular disease. 

Chiavaroli says the study findings also align with Health Canada’s dietary guidelines that encourage people to choose plant-based proteins more often, a move that would also convey benefits for the environment.

“We hope our study will help people feel more comfortable including soy foods in their diet without being concerned that it’s going to increase their risk of estrogen-dependent cancer,” says Chiavaroli.

*Although menopause is sex-specific, we use the term women here to reflect the original study and the published trials it references. We recognize that some persons experiencing menopause may identify differently than with this gender.

This study was funded by the United Soybean Board (United States Department of Agriculture) and the Canadian Institutes of Health Research through the Canada-wide Human Nutrition Trialists’ Network. 

 

Study finds genetic mechanisms behind high-yield apple trees




Boyce Thompson Institute
Fuji Apple 

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Fuji apples growing in a sustainable orchard

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Credit: Yuri Arcurs




Apples rank among the world's most valuable fruit crops, with production spanning more than 100 countries. Some apple trees naturally develop into what farmers call "spur-type" varieties—compact trees that are more productive and easier to maintain. But the genetic mechanisms underlying this coveted trait have remained elusive—until now.

An international team of researchers began by creating the first "fully phased" genome of the popular Fuji apple—essentially a complete genetic blueprint that clearly distinguishes between genes inherited from each of the two parents.

With this new blueprint in hand, the team studied 74 Fuji clonal varieties and identified significant somatic variations—mutations that occur during the plant's lifetime rather than being inherited. Somatic variations can lead to new traits, and in apples, it's the reason we see trees with unique characteristics like early maturation or the spur-type growth habit.

"Farmers prize spur-type apple trees," explained Zhangjun Fei, professor at the Boyce Thompson Institute and one of the study's lead authors. "They exhibit more concentrated flower bud formation and increased fruit yield while requiring less pruning. This makes them ideal for modern orchards, especially in challenging growing conditions."

The Fuji apple, which originated in 1939 as a cross between the Red Delicious and Ralls Janet varieties, is known for its sweet flavor and crisp texture. In countries like China, where over 70% of apple cultivars are based on Fuji clones, spur-type varieties have boosted productivity and adapted well to areas with poor soil and frequent drought.

The study’s key discovery centers around a gene called MdTCP11, which acts like a growth control switch. The researchers found that compact apple trees have a small but significant deletion in the DNA near this gene, which causes it to become more active and results in shorter branches and a more compact tree structure.

But the story doesn't end there. The researchers also discovered that the DNA methylation levels—a process that can turn genes on or off—were lower in spur-type varieties compared to standard types. This lower methylation level allows MdTCP11 to be more active, further enhancing the spur-type characteristics.

This research could have significant implications for apple breeding. Understanding these genetic traits could help breeders develop apple varieties that combine compact growth with other valuable characteristics, such as disease resistance.

It could also lead to more sustainable apple production, as compact trees require fewer resources to maintain and can produce more fruit in a smaller space. It's a perfect example of how understanding the genetic code of our food crops can lead to more efficient and sustainable farming practices.

The study was recently published in the journal Nature Communications.