Science of Food: The story with soy
Science of Food
Our bodies contain millions of proteins. Proteins are made up of long chains of amino acids and we all have a unique set of proteins derived from our DNA. In addition to their structural role building muscle mass and connective tissue, proteins are responsible for carrying out nearly all the functions in our body, from transporting oxygen to regulating cell division to mediating the immune response (see previous column “Eat your Electrons” at summitdaily.com). Like tiny molecular machines, they receive specific “signals” that can either turn on or turn off its given function.
To understand how this works, think of a lock and a key. Only a specific key can unlock a door because the key has the right shape to fit into the lock. Proteins work by a similar mechanism, each with a specific three-dimensional shape. When the right key comes by, it fits into the protein’s lock and can open the door to either activate or deactivate its function.
The estrogen receptor is a notorious example of a protein that plays a role in the normal functioning of the human body, for example in reproduction, body fat distribution, bone health, and general metabolic and cardiovascular health. Estrogen itself is the primary female sex hormone (actually comprised of multiple molecules) and is the body’s natural key to the estrogen receptor. Numerous other “estrogen-like” molecules are also known, both man-made and found in nature, that all have a similar shape to the natural estrogen hormone. This shape complementarity allows these molecular keys to unlock the door to the promiscuous estrogen receptor to either turn on or turn off the functions described above.
Overactive estrogen receptor signaling may also drive tumor formation and the progression of cancer. This occurs when the key that fits into the lock leads to increased cell growth. Not all keys activate growth. Many can block estrogen or estrogen-like compounds from unlocking the door to activate this function (e.g. tamoxifen), which is how hormone-based therapies work for treating cancer.
There are literally thousands of unique so-called “phytoestrogens” (the word “phyto” is derived from the Greek word for plant) found in over 300 different foods that have a similar shape to natural estrogen and fit into the lock of the protein. The estrogenic activity of most phytoestrogens is usually inherently lower than estrogen itself and the diverse range of compounds (e.g. lignans, isoflavones, and coumestans) are typically found in small doses in whole foods.
However, some foods like soybeans and flaxseed have relatively high concentrations of phytoestrogens and there is currently some controversy around the ability of these estrogen-like molecules to influence cancer progression. The single isoflavone compound genistein present in soy is perhaps one of the most widely studied phytoestrogens. When examined in the laboratory or the clinic, genistein acts similarly to the drug tamoxifen, effectively turning off estrogen receptor activity and shutting down cell growth. In addition, epidemiological studies examining Japanese people with a diet rich in soy show a low incidence of hormone-dependent cancers, suggesting soy’s protective role.
There are too many phytoestrogens with such different and interdependent physiological behaviors to tease out the activity of each one individually. Most of the evidence shows that soy and phytoestrogens in general are beneficial. Perhaps the conflicting conclusions on soy’s role in cancer are due to the fact that man-made soy products such as soy lecithin, soybean oil, soy protein powder and genetically-modified soy are present in so many modern foods and those concentrated and modified forms of soy may interact with the estrogen receptor differently than whole soybeans. Soy isoflavone supplements have also become widely available due to its known estrogenic activity. I would suggest eliminating those synthetic sources of soy, especially those with existing breast cancer.
Isn’t it interesting that plants contain natural substances that look just like the human hormone estrogen? Any substance that we consume has the potential to act as a key to unlock proteins. The soy story represents just one example of how food can react in the body to modulate biological function via this lock and key mechanism. Imagine what the other foods you are eating can do!
Dr. Lisa Julian Ph.D. has a passion for organic chemistry the “molecules of life,” and its application to food and health. She’s the owner of Elevated Yoga & Holistic Health in Frisco and teaches Science and Nutrition at CU Denver and CMC. She can be reached at (970) 401-2071 or email@example.com For more information about services offered at her studio, visit www.ElevatedYogaColorado.com.
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