Soy and Cancer
June 24, 2021Soy and Cancer
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Information
Susan Pritchard Downie, RD, a dietitian at Smilow Cancer Hospital Care Center in Greenwich, discusses the myth that soy causes cancer.
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- 00:00Hello I'm supercharged Downey,
- 00:02the outpatient oncology dietitian at
- 00:05Smilow Cancer Care Center in Greenwich.
- 00:09The myth I'd like to address is that soy
- 00:12causes cancer and that people with cancer,
- 00:15especially with breast cancer,
- 00:18should avoid soy.
- 00:19It's clear to see how this
- 00:22myth arose 25 years ago,
- 00:24studies showed that isoflavones in soy
- 00:28caused breast cancer cell growth in rodents.
- 00:31Spoiler Alert the lab animals were rats.
- 00:36Researchers then,
- 00:37recognizing that isoflavone molecules
- 00:39were similar to the hormone estrogen.
- 00:42Called them phytoestrogens,
- 00:45meaning plant estrogens.
- 00:48Since high blood levels of estrogen
- 00:50are linked to breast cancer risk,
- 00:53they concluded that soy isoflavone flavones
- 00:56could increase breast cancer risk in humans.
- 01:00Did you catch the flaws in their reasoning?
- 01:03It wasn't until soy research moved from
- 01:06lab animals to humans that scientists
- 01:09realized that humans metabolize soy
- 01:12isoflavonoids much differently from rats.
- 01:15Instead of increasing estrogen levels.
- 01:18So I also offer isoflavones more often,
- 01:21do the opposite.
- 01:23They bind to an estrogen receptors
- 01:26which blocks estrogen action.
- 01:29In fact,
- 01:29recent studies show that a diet that
- 01:32includes soy may even reduce the
- 01:35risk of developing breast cancer.
- 01:38So what about the risk for other
- 01:41cancers and for cancer survivors?
- 01:44Population studies show that short either
- 01:46no effect or decreased effect of on
- 01:50prostate cancer in men who eat soy foods.
- 01:54There is limited evidence that soy
- 01:56might help protect against lung cancer.
- 01:59And population studies don't link
- 02:01soy with the risk of any cancer.
- 02:04Similarly, studies of breast and
- 02:08prostate cancer survivors showed
- 02:10no harmful effects from soy.
- 02:13Population studies show that women who
- 02:16eat moderate amounts of soy may even
- 02:19have improved overall survival and
- 02:21decreased recurrence rates.
- 02:23Some preliminary studies suggest that
- 02:26soy foods may be protective against.
- 02:29Breast cancer protective for those
- 02:32with breast cancer survivors
- 02:34who are taking tamoxifen.
- 02:36Controlled clinical trials of men with
- 02:39prostate cancer who used soy protein or
- 02:42soy isoflavones showed either no effect
- 02:44or decreased program.
- 02:45Progression of their cancers.
- 02:50But aren't processed soy foods unhealthy?
- 03:00Minimally processed soy foods like these.
- 03:05Immature. Sleeping pods.
- 03:07Called by the Japanese name Iida Mommy.
- 03:13Roasted and canned mature soybeans.
- 03:17And toasted eda mommy. Are rich
- 03:23sources of. Nutrients
- 03:25including fiber, protein B,
- 03:28vitamins, magnesium and potassium.
- 03:35Well, tofu and soymilk are lower
- 03:38in fiber due to processing.
- 03:40There's still good sources of calcium
- 03:42and plant based protein and their
- 03:45cholesterol free and low in saturated fat.
- 03:50So oil, soy sauce and soy lecithin
- 03:55are also processed soy foods.
- 03:58They contain little or no
- 04:02protein and no phytoestrogens.
- 04:05So my protein isolate is a
- 04:08very highly processed soy food.
- 04:10You may have seen it as an ingredient
- 04:14in high protein drinks and shakes,
- 04:17and in meatless burgers and sausages.
- 04:24Until recently, it was assumed
- 04:26that foods made from soy protein
- 04:28isolate could be risky because
- 04:30they would contain unnaturally
- 04:32high levels of isoflavones higher
- 04:34than those that occur naturally.
- 04:37In foods like traditional
- 04:39foods like edamame and tofu.
- 04:41But when they were actually analyzed,
- 04:44it turns out that soy protein
- 04:46isolates are no higher in isoflavones
- 04:49than plain old boiled soybeans.
- 04:51It turns out that up to 80% of
- 04:54isoflavones are lost in processing.
- 04:57So foods made with soy protein
- 04:59isolate can be another way to add
- 05:02plant protein to your diet so it
- 05:04will be lower in fiber and other
- 05:06nutrients than the less less
- 05:08processed soy foods you see here.
- 05:13Check the ingredient list and nutrition
- 05:14facts to see how they fit in your.
- 05:17If they suit you.
- 05:19In summary, soy is safe for cancer survivors,
- 05:24including breast cancer survivors,
- 05:26a position supported by the
- 05:29American Cancer Society.
- 05:31The American Institute for Cancer Research
- 05:34check out their great website at aicr.org.
- 05:39Harvard TH school.
- 05:41Harbitz TH Chan School of Public health.
- 05:45The Dana Farber Cancer Institute and my
- 05:49professional organization of oncology
- 05:52addition dietitians at oncologynutrition.org.
- 05:55Including soy foods in your diet can
- 05:59help you to increase your fiber intake.
- 06:03Add starting so I foods in your
- 06:05diet can help you to add fiber,
- 06:08decrease saturated fats and
- 06:09increase your plant protein intake.
- 06:11Don't let outmoded ideas about
- 06:13soy foods keep you from enjoying
- 06:16them as part of your healthy diet.