Ask the Diet Doctor: The Last Word on Soy Protein Isolate

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Q: Should I avoid soy protein isolate?

A: Soy has become a very controversial and complicated topic. Historically Asian populations have consumed large amounts of soy products while also having the longest and healthiest lives in the world. Research regarding soy protein and cardiovascular health became so robust that it was awarded a health claim, allowing food companies to state that “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of (name of food) provides X grams of soy protein.”

But for every health benefit of this complete plant-based protein source, you’ll also hear of a potential detrimental effect, including an increased risk of certain cancers, disturbed hormonal balance, disrupted thyroid function, or intake of pesticides and toxins.

Easing some concerns, the Agency for Healthcare Research and Quality (AHRQ) released a nearly 400-page report on the effects of soy and soy isoflavones (antioxidants found in soy), concluding that, “For all outcomes, including adverse events, there is no conclusive evidence of a dose-response effect for either soy protein or isoflavone.” However, because soy products come in such a wide variety-whole soy, fermented soy, soy protein isolate, and others-confusion continues to ensue.

RELATED: 6 Satisfying Soy-Free Vegan Smoothies

Soy protein isolate in particular has been increasingly placed under a health microscope regarding its safety, due to its widespread use to increase protein content of various foods or to enhance texture. There are three common concerns to be aware of.

1. Metal contamination. Soy protein isolate is extracted from defatted soy flour. It is made of almost pure protein, since the isolation process yields a product that is 93 to 97 percent protein, leaving minimal fat and carbohydrates. The concern about the isolation process centers on the fact that aluminum found in the giant vats used to isolate the soy protein may leach into the protein itself, increasing the likelihood of heavy-metal poisoning. This is completely speculative, as I have yet to see an analysis of soy, whey, or any protein isolate showing heavy metal contamination from the containers used during the isolation process.

2. Pesticide risk. Ninety percent of genetically modified soy is resistant to glyphosate, the pesticide found in Round Up. A concern raised about eating products with soy protein isolate is that you will consume excessive amounts of this chemical. The good news? Glyphosate is not well absorbed by the human GI tract, the potential negative effects on humans are dose-dependent, and the level of that dose is very controversial.

The other good news (or maybe bad news) is that when it comes to glyphosate, soy protein isolate isn’t your main problem. Glyphosate is everywhere, which is the really bad news! It is like BPA, which I’ve covered previously. Research published in 2014 in Food Chemistry and Environmental & Analytical Toxicology highlighted the fact that the worldwide use of glyphosate has made it abundant in our ambient environment and food supply. While the amount of glyphosate in a serving of soy protein isolate has not been quantified, it is very unlikely soy it is your primary, only, or even a significant source of exposure of this pesticide.

RELATED: 6 New Ways to Eat Tofu

3. Concentrated isoflavones. One of the most controversial areas of soy, isoflavones are antioxidants that are famous for mimicking estrogen in the body. This effect has been seen as a benefit, with research showing that 75 or 54 milligrams a day (mg/d) of soy isoflavones can increase bone mineral density and decrease the frequency and severity of hot flashes, respectively. However, isoflavones in soy have also been proposed to play a role in increasing risk of breast cancer. The research in this area is complicated and constantly evolving, with negative effects seen in animal studies, but no effects found in human studies.

It’s also important to note that soy protein isolate isn’t necessarily a concentrated source of isoflavones. According to the USDA Isoflavone Database, one ounce (about one scoop) of soy protein isolate contains 28mg soy isoflavones and three ounces of cooked tofu contain 23mg soy isoflavones. On a per-serving basis, both foods contain about the same dose of isoflavones, but soy protein isolate contains significantly more protein: 23g vs. 8g.

All things considered, eating moderate amounts of soy protein isolate does not provide a health risk. I see the main benefit of soy protein isolate as a nutritional tool to help you meet your daily protein needs. If you abstain from eating dairy protein (whey) right after a workout or if you need to increase the protein at a given meal, use soy protein as you would use any protein supplement.

  • By Dr. Mike Roussell

Is Soy Protein Isolate Bad for You?

Before you chomp on your next veggie burger or tofu dog, there’s something you should know. Those, and other soy-based foods often considered part of a healthy diet, contain soy protein isolate (SPI), soy’s heavily processed stepchild.

Here’s why you should avoid it.

“There is a lot of controversy around soy and whether or not it’s good for you,” says Devi Moss of Simply Whole by Devi. “But the real controversy lies with soy isolate, not whole food soy products like organic tofu and whole soybeans.”

The health coach steers clear of processed foods, including foods that contain soy protein isolate.

“It is truly best to eat whole foods with all the synergies in the food as opposed to isolating food components,” Moss says.

Generally, soy protein isolate is made from de-fatted soybean flakes that have been washed in either alcohol or water to remove sugars and dietary fiber. This process strips the pure soybean of its nutrients.

“This is a problem with a lot of our foods today,” says Moss. “They have become so manipulated that they’re unhealthy.”

Side effects of soy protein isolate

In animal studies, soy isolate has been linked to allergies, thyroid problems, and even brain damage. Soy has been labeled one of the top seven allergens for people to avoid, as soy isolate is found in a lot of processed foods, including bread and baked goods, soups and sauces, and breakfast cereals and protein bars. There have also been several studies on soy protein and age-related dementia, although many of those studies have been inconclusive.

Benefits of pure soy

Research shows that roughly 25 grams a day of soy protein is enough to lower LDL or ”bad” cholesterol by about ten percent in people who start out with an LDL above 160. And a comprehensive study on menopause found that two daily servings of soy reduced the severity and frequency of hot flashes. As a healthful meat substitute, Dr. David L. Katz recommends eating pure, non-GMO soy foods such as tofu, edamame, tempeh and soymilk in moderation, meaning two to three soy-based meals per week.

Opt for fermented soy

Fermentation increases the digestibility of soy, adds good bacteria and reduces the plant estrogen content in soy foods. Fermented soy includes miso, natto and tempeh.

The soy and cancer connection

Dr. Katz says the evidence linking soy intake with breast cancer is mixed. When researchers compare the Japanese, who eat a lot of soy, to Americans, who eat very little, they find lower rates of breast and other cancers in soy eaters. Yet in test tube studies, soy’s plant estrogens accelerated cancer cell growth. One theory is that soy can have both positive and negative influences on breast cancer.

Will you avoid foods with soy protein isolate?

Soy Protein Isolate

Soy protein isolate is a dry powder food ingredient that has been separated or isolated from the other components of the soybean, making it 90 to 95 percent protein and nearly carbohydrate and fat-free.

In the Market

Soy protein isolate is used in making a variety of foods. It may be found in:

  • dairy-type products such as beverage powders, infant formulas, liquid nutritional meals, and some varieties of liquid soymilk
  • bottled fruit drinks
  • power bars
  • soups and sauces
  • meat analogs that resemble conventional foods in color, texture and taste
  • breads and baked goods
  • breakfast cereals
  • many weight and muscle gain products in the fitness market.

Soy protein isolate can be purchased as flavored or plain soy protein shake powder.? Several brands are fortified with calcium and other minerals and vitamins, along with sweeteners and flavorings. Individual, single serve packages are the utmost in convenience for busy consumers. The most economical form of soy isolate is plain powder, with no other ingredients added.

Soy protein isolate is sold in the health food section or the pharmacy within the regular supermarket. Natural food supermarkets and health food stores carry the widest variety of products. Other sources for soy protein isolate powders are mail order, food cooperatives, buying clubs, online shopping and mass-market stores.

Give Me Five

  1. Enjoy a high-protein energy bar with soy protein isolate.
  2. Make a soy smoothie by mixing vanilla soy protein isolate powder into unsweetened soymilk along with berries, mango or peach chunks.
  3. Create a power-packed bowl of oatmeal by adding honey roasted soy nuts, a couple scoops of soy protein isolate powder and chopped dates or raisins to hot oatmeal.
  4. Boost protein in macaroni and cheese, casseroles, soups or stews by stirring in a couple servings of plain soy protein isolate powder.
  5. Sprinkle soy protein isolate powder on cold cereals to keep you fuller longer in the morning and give you a boost of energy.

In the Kitchen

Soy protein isolate beverage powder is an easy way to incorporate soy protein into the diet. Kept sealed and dry, the powder is shelf-stable for many months. Look for use-by dates on the container.

Nutrition Highlights

Soy protein isolate supplies a high quality of protein that contains all essential amino acids needed for growth. Soy protein isolate is equal in quality to animal products and is almost fat free containing less than 1 percent fat and unlike animal products contains no cholesterol and little or no saturated fat.

In addition to the excellent quality of soy protein, scientists have found that soy protein may help reduce the risk of heart disease by lowering blood cholesterol and increasing the flexibility of blood vessels. The FDA has approved a health claim stating that “25 grams of soy protein in a daily diet low in saturated fat and cholesterol can help reduce total and LDL cholesterol that is moderately high to high.” Much of the human and animal research on the health benefits of soy has been conducted using isolated soy protein and should testify to its short-term safety and efficacy.

Important bio-active components found naturally in soybeans are being studied in relationship to relieving menopausal symptoms, such as hot flashes, maintaining healthy bones, and preventing prostate, breast, and colorectal cancers. The content of bio-active components in soy protein isolate varies from product to product depending on how the soy protein is processed.

The Making of Soy Protein Isolate

Advances in processing technology have led to a variety of ways soy protein isolate can be produced. Generally, soy protein isolate is made from de-fatted soybean flakes that have been washed in either alcohol or water to remove sugars and dietary fiber. Soy protein isolate is used through out the food industry for both nutritional and functional reasons.

NUTRITION FACTS

1-ounce plain soy protein isolate powder provides:
Calories: 96 % Daily Value
Total Fat 1g 2%
Saturated Fat 0g 0%
Total Carbohydrates 2g 1%
Protein 23g 46%
Cholesterol 0mg 0%
Sodium 285mg 12%
Dietary Fiber 1.5g 6%
Calcium 50mg 5%
Potassium 23mg 1%
Phosphorus 220mg 22%
Folate 50mcg 13%
Source: USDA National Nutrient Database for Standard Reference, Release 17 (2004)
Isoflavone, 28mg
Source: USDA -Iowa State University Database on the Isoflavone Content of Foods,? Release 1.3, 2002, USDA Nutrient Data Laboratory Agricultural Research Service
Exchanges: 3 lean meat/meat substitute
Source: Based on information from Exchange Lists for Meal Planning, 2nd edition, 2002.
The American Diabetes Association/The American Dietetic Association

Confused about eating soy?

News briefs

Published: March, 2018


Image: © hanhanpeggy/Getty Images

The FDA wants to pull its support of the health claim that eating soy protein may help reduce the risk of heart disease. The agency proposed the change last fall, citing evidence that questions whether there’s any real benefit to heart health. If the FDA goes through with the move, then food makers will no longer be allowed to market soy products with the claim that they can help your heart. But soy won’t hurt your heart, and soy does have other benefits. “It’s high in polyunsaturated fats, fiber, vitamins, and minerals, and low in saturated fat. Natural soy products — like tofu or edamame — could replace red meat and other animal sources of protein higher in saturated fat,” says dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women’s Hospital. One caveat: some soy products contain estrogen-like chemicals that could have adverse effects. So stay away from soy isoflavone supplements and foods made with textured vegetable protein and soy protein isolate, found in many protein powders and nutrition bars. Still, McManus says it’s okay to eat whole soy foods — like soy milk, edamame, and tofu — in moderation, several times per week.

Disclaimer:
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

6/6 Photo: Pexels

It may upset your stomach

Many people have allergies or intolerances that make it hard to digest soy. But even if you’re not one of them, soy protein isolate may make your stomach rumble, says Slayton. This is because SPI has a higher concentration of trypsin inhibitors, chemicals that reduce available trypsin—an enzyme that helps digest protein—in the body.

So what to do if you’re a soy-loving vegetarian? Skip products with SPI and opt for “natural, whole protein sources like beans, lentils, nuts, and seeds, and organic, non-GMO natural sources of soy like edamame, tofu, and tempeh,” Middleberg suggests.

Slayton also suggests sticking to fermented soy sources, like miso, tempeh, and natto. “Fermentation increases the digestibility of soy, adds good bacteria, and reduces the plant estrogen content in soy foods,” she explains. And in the end, both nutritionists agree: Like most things, soy is best enjoyed in moderation—and sticking to whole (rather than processed) foods is always a good plan.

Looking for other ways to get your protein that don’t involve meat (or soy)? Here are five surprising plant-based protein sources. And if you’re confused about genetically modified organisms? Here’s everything you need to know about GMOs.

When it comes to recovery from exercise, building lean muscle, and living a strong, healthy lifestyle, getting enough protein is absolutely vital.

And a good protein powder can help you get enough protein powder in your day. But which protein powder is the right one for you?

Your options seem endless. If you walk into a store you’re bound to find 20 different brands with 20 different ingredients. So what’s the best decision to make regarding your protein powder?

Is soy protein isolate or non-soy plant-based protein powder the best buy for your body?

When it comes to living a clean, plant-based diet, these are really the only two choices for you. That by no means is a bad thing. It actually helps you narrow down your decision.

You need to get your protein from somewhere, so it’s best to start looking a little more closely at these two different options.

IdealRaw Protein Powder is a plant-based protein shake that is both delicious and awesome. Each serving gives you 15g of protein, 5g of fat, and only 130 calories!

Why We Need Protein

Proteins are the building blocks of life. They make up everything from our muscles, skin, and even hair. They are so important in the way our bodies work and repair themselves.

Not only does protein play a major role in recovery from exercise, but it also helps facilitate many cellular processes, makes certain enzymes and hormones, and helps our body repair itself from injuries!

Protein is essential to optimal health and wellness.

Proteins can be broken down further into what are known as amino acids. Out of the 20 amino acids found in our bodies, there are nine that our bodies cannot create on their own. We need food to help with that.

Here’s a list of the essential nine:

    • Histidine
    • Isoleucine
    • Leucine
    • Lysine
    • Methionine
    • Phenylalanine
    • Threonine
    • Tryptophan
    • Valine

Organic Vegan Protein🌱

IdealRaw Organic Protien is delicious, plant-based, and a smooth taste and texture that you’re sure to love!

Soy has been such a popular protein option for vegans and vegetarians up until recently. It’s commonly used in many Asian countries and has become a major staple here in the States. You can find it in your meals, various drinks, protein bars, and of course, in your protein powder.
There are so many different soy products out there. One of the most common forms of soy is soy protein isolate. This is what you’ll find in your soy protein powder. It contains about 90 percent of protein from soybeans.

How is it made, though?

How Soy Protein Isolate Is Made

There are actually a few different ways to make soy protein isolate, but the most common way is pretty disturbing.

Through a process called hexane extraction, the fats are separated from the soybean. This hexane bath the soybeans soak in is actually super dangerous.

Hexane is a gasoline byproduct that is extremely explosive. The USDA has also labeled it as a neurotoxin. In fact, the USDA won’t even allow for its use in organic foods. Sadly though, non-organic foods that contain soy still use the hexane extraction method.

The process doesn’t just stop there.

Once the fats are removed from the soybean, it’s then soaked in an ethanol or an acidic bath to remove carbohydrates and any lingering flavor.

The final result is the 90 percent soy protein isolate you get in your non-organic protein powders.

Now, I’ll be completely real with you. There are plenty of soy products that don’t allow hexane extraction. If you buy only organic soy products you shouldn’t have to worry about that scary neurotoxin entering your body.

But are there other problems with soy?

Other Health Risks of Soy Protein Isolate

If the way that soy protein isolate is made isn’t scary enough, there are also some other problems you might want to think about before you eat that tofu burger or buy that soy protein powder.

Phytoestrogens

Soy contains high levels of phytoestrogens. They act a lot like estrogen hormones and when consumed in large quantities, can cause major hormone imbalances which result in many other problems.

Both men and women have estrogen; women just have higher levels. Increasing these hormone levels for both genders can cause fertility issues, as well as various cancers.

Goitrogens

Soy protein isolate can also cause problems for your thyroid. It contains a chemical known as goitrogen, which can affect the hormones needed to boost your metabolism. This can lead to weight problems and other concerns.

I hope you’re starting to see the effects that soy can have on your health. Since soy is found about 60% of our processed food, you’re probably getting more soy than you think.

Just in case you want more information, here’s a to other known problems soy can have on your body.

Soy Free Plant-Based Protein

Unlike soy protein isolate, soy free plant-based protein happens to be a lot safer, as long as you are getting everything you need.

Remember those nine essential amino acids you need for your body to work properly? In order to get all nine of them from plants, you need to mix and match different vegetables and grains. This can seem like a hassle, but it actually isn’t too difficult.

Some plant-based protein powders will actually have multiple plant proteins to help you get the full spectrum of essential amino acids. Here are some common plant protein sources:

  • Peas and Coconuts
  • Hemp and Chia Seeds
  • Brown Rice and Quinoa
  • Beans and Nuts

Of course, there are other types of plant protein, but these just happen to be commonly used in most plant-based protein powders.

Benefits of Soy Free Plant-Based Protein

If you’re looking for a clean, natural way to incorporate protein into your diet without turning to animal protein, soy free plant-based protein, like IdealRaw, is definitely the way to go.

As long as your protein powder gives you all nine amino acids, your post-workout drinks shouldn’t have a problem helping you recover and build muscle.

Nutrient Rich

A big plus for choosing plant-based protein over other types of protein powder is the added vitamins and minerals you get.

Fruits and vegetables are naturally full of many types of vitamins and minerals that are good for your health.

They’re also rich in antioxidants and fiber. Eating plenty of fruits and veggies can help boost immune health and other necessary functions to keep your body working properly.

If you aren’t a huge fan of fruits or vegetables, plant-based protein powders are a great way to get the nutrients you need.

Lean Protein

Plant protein contains much less fat than other forms of protein. Combine that with large amounts of fiber, and your body has a better chance at regulating or losing weight.

Part of weight loss means eating larger amounts of protein. Protein requires more energy to breakdown than other foods, which is why nutritionists and trainers will tell you to up your protein intake.

Of course, all of us need some fat in our diets. Plant protein still contains fat, but it’s much healthier than other forms of protein.

What to Look out for

Like with almost all foods, not all are created equal. If you want to get the best plant-based protein powder (like I recommend you should do), there are a few things that you should watch out for.

Artificial Ingredients

If you don’t want to fall into the artificial chemicals and ingredients trap like you would with soy protein isolate, check for plant-based protein that is free from any weird additives.

A good rule of thumb is to check the ingredients on the label. If there are ingredients that you’ve never heard of before or don’t know how to pronounce, there’s a good chance it might contain something artificial.

Look for protein powders that are certified organic. IdealRaw’s protein powder is USDA certified organic, so you know that you’re getting a protein powder that’s natural and artificial free.

Sugar Source

Most protein powders have lots of sugar to help with taste. If you’re like me, you want a protein powder that isn’t filled with sugar.

There are also many different types of artificial sweeteners that are placed in your post-workout shakes as well. Although, not all artificial sweeteners are necessarily bad, you may want to try to keep it as natural as possible.

Look for protein powders that have sweeteners like stevia. It’s an all-natural sweetener that goes a long way with just a little amount. You won’t be spiking your blood sugar or adding tons of calories by doing so.

Say No to Soy Protein Isolate

Now that you’re a protein powder guru, you should have no problem picking an option that is best for you.

Soy protein isolate may be a super common choice of protein to buy, but it comes with a lot of downsides. Don’t get caught up in convenience. There are better options!

Make plant-based protein your best friend! Unlike soy protein isolate, it’s all-natural and perfect for gaining muscle, losing weight, and maintaining a healthy diet. You get so many other benefits besides more protein as well.

If you’re looking for the best plant-based protein out there, IdealRaw Protein is the way to go. IdealRaw made sure to give you all essential amino acids, a bunch of health-boosting superfoods, and a completely natural, artificial-free protein. It really is the best protein shake out there! So don’t wait, get yourself some today!

Gnc GNC Pro Performance(r) 100% Soy Isolate – Creamy Vanilla

The dosage chart on the label is a recommendation by GNC Scientists for the best results from 100% Soy Isolate. It is recommended that the minimum daily dose is taken on each day based on activity level. Pro Performance(r) 100% Soy Isolate is a protein shake that is cholesterol-free, with no lactose, and is from vegetarian sources. Soy protein is one of the most anabolic proteins. One of the biggest misconceptions behind this protein is the link to estrogen production; however, it contains all of the essential amino acids, including BCAA. BCAA may help preserve muscle glycogen stores and reduce the amount of protein breakdown during exercise. This formula features Supro(r) soy protein, one of the most clinically studied so proteins. Supro(r) is made from soybeans that are produced while being tightly monitored and controlled from planting through processing. The Pro Performance(r) Results Advantage Protein is an essential nutrient that is necessary for the growth, repair and maintenance of body tissues such as skin, bones and muscles. Studies have shown that soy protein taken by active individuals helps support muscles during exercise. Additionally, diets low in saturated fat and cholesterol that include 25g of soy protein a day my reduce the risk of heart disease. One serving of Pro Performance(r) 100% Soy Isolate features 25g of protein providing an equivalent nitrogen factor of 25. Soy Protein is an effective source of nitrogen for fueling lean muscle mass. Your muscles can only grow when your body retains enough nitrogen. This formula delivers naturally-occurring anabolic amino acids into your bloodstream. This spike in aminos provides nitrogen and subsequently creates a nitrogen-rich environment needed for maximum muscle protein synthesis. Protein synthesis is crucial to the building of lean muscle mass. The Pro Performance(r) Quality Advantage GNC Pro Performance(r) 100% Soy Isolate is also tested

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  35. Sathyapalan T, Manuchehri AM, Thatcher NJ, Rigby AS, Chapman T, Kilpatrick ES, Atkin SL. The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism: a randomized, double-blind, crossover study. The Journal of Clinical Endocrinology & Metabolism. 2011 May 1;96(5):1442-9.

PMC

Isoflavone Variables and Risks

Soy research is complicated because there’s considerable variation in isoflavone exposure among people classified as soy consumers. Agronomic factors (such as the soybean cultivar and the environmental conditions under which the crop grew) affect a food’s isoflavone profile, as does the way a soy food is processed. For example, soy protein concentrate produced by alcohol extraction may have only 12.5 milligrams (mg) total isoflavones per 100 g, in contrast to the nearly 199.0 mg total isoflavones per 100 g of full-fat roasted soy flour. Additionally, the fact that most of the isoflavones in food occur bound to sugar affects how they are digested.

Once genistin enters the digestive tract, it releases its sugar and becomes “free” genistein. Some of this free genistein is absorbed. However, most is reconjugated into glucuronides or sulfates, the primary circulating forms of genistein, which are thought to have either low or no biological activity. Only a very small amount of free genistein escapes conjugation by the liver and circulates in that form.

“People need to know that as it occurs in soy and other plant products, genistin is the compound that’s there. The amount of actual genistein is very low, one percent or less probably,” says Michael Shelby, director of the National Toxicology Program’s Center for the Evaluation of Risks to Human Reproduction (CERHR). Key exceptions are fermented products, such as miso and tempeh, which may contain up to 40% free genistein.

Several researchers say that figuring out the pharmacokinetics of genistin and genistein is a vital piece of missing information. “It’s a matter of finding out how much genistin is converted to genistein in the digestive system, and that information is not known,” says Jefferson. “I don’t think a lot of this was understood years ago when some of the animal experiments started, and at that time we didn’t have a clear understanding of the metabolism and fate of these chemicals. We did the best we could, as a community, to try to use the compound we thought would be the one we should look at. I think it’s given us some excellent starting types of data, where we know that these compounds are capable of causing reproductive and developmental effects.”

According to Thomas Badger, director and senior investigator at the Arkansas Children’s Nutrition Center in Little Rock, however, these effects are seen only under certain experimental conditions that are not likely to occur in humans—and therein lies the crux of the debate. Criticisms of many studies of genistein’s effects on reproduction and development have centered on exposure occurring by injection and consequently bypassing the usual metabolic pathways. There is also disagreement about the use of neonatal mice—commonly used in studies of reproduction and development—as a suitable model for predicting effects in human infants.

Despite these criticisms, Newbold stands by her data. “There was some confusion on the fact that in all of our work we have injected genistein,” she says. “We went back and did some of the pharmacokinetics with that to show that the total circulating amounts of genistein are very similar to what’s been reported in feeding rats and also in infants. Metabolism doesn’t have to be the same, but you have to know that the active compounds are getting to the target tissue. Ultimately, a mouse and a rat are not the human, though. You just have to accept it and be as careful with your extrapolations as possible.”

Further controversy surrounds the fact that most of the epidemiologic studies of Asian populations involved whole soy foods, but animal and human intervention studies have generally used soy concentrates or isolated isoflavones; some animal studies used pure genistein. This difference may have obscured what the health effects of soy actually are.

“I’m reasonably sure that any time you take one of those isoflavones and give it separately, you don’t see the same effects as when all three of the isoflavones of soy are given,” says Kaplan. “Based on everything that we know, the best health effects probably come from the whole isolated soy protein given together. There’s something about the intact product that seems to be bioactive that is not able to be replicated when you begin chopping it up.”

In Expert Panel Report on the Reproductive and Developmental Toxicity of Genistein, a March 2006 review of the literature on this compound, an expert panel convened by the CERHR scrutinized what has been learned about human exposure to genistein and the associated reproductive and developmental consequences. The most highly exposed adult population was Japanese, with a daily average intake of 0.43 mg per kilogram body weight, which was approximately 10-fold less than the no-effect levels found in rodent studies. Based on the conclusions presented at a meeting held on 15–17 March 2006, the panel found little cause for concern about human exposure to genistein. However, no consideration was made for the amount of genistin found in the diet or how much of it is hydrolyzed in the digestive system to genistein. Further, the panel’s conclusions were not unanimous.

Considerably less attention has attached to daidzein, though there are currently indicators that it may play a larger role than genistein in soy’s apparent beneficial health effects. Like genistein, daidzein in soy exists primarily in linkage with a sugar molecule. This complex, daidzin, is hydrolyzed and the sugar molecule removed in the gut. Daidzein can also be conjugated to glucuronic acid or sulfate in the gut and liver. It may also be converted to equol (suspected of having a higher estrogenic potency than the original daidzein) by gastrointestinal bacteria. There is considerable variability in individuals’ ability to produce equol, and the metabolic pathways for both genistein and daidzein may vary due to factors such as a person’s particular microflora, intestinal transit time, and current or recent use of antibiotics and other drugs.

Thomas Clarkson, a professor of comparative medicine at the Wake Forest University School of Medicine, points out that although soy protein has a very large beneficial effect on cardiovascular health in monkeys, the effects are much less clear in women. Daidzein metabolism may be the key.

“Our best clue is that all monkeys are equol producers, but only about twenty-five or thirty percent of women are equol producers,” Clarkson explains. “There’s some suggestion now that those women who are equol producers do derive some cardiovascular benefits. The fact that so profound in monkeys may have to do with the fact that they’re all equol producers, and may only be translatable to the women who are equol producers.”

There have been only a few studies that have looked exclusively at glycitein, the third soy isoflavone, but those have not been on health effects. There are indicators from a couple of recent in vitro studies that glycitein may be protective of bone. Most glycitein research has focused on determining how to detect the compound, and its estrogenicity and metabolism.

Vitacost Natural Vanilla Flavored Soy Protein Isolate Protein Powder

What is Isolated Soy Protein Powder?

Isolated Soy Protein Powder is an easy-to-use powdered drink mix that makes delicious shakes packed with 15 grams of soy protein per serving. Ideal for vegetarians or those with allergies or sensitivities to other high-protein foods (such as dairy or eggs), Isolated Soy Protein Powder can be easily blended with water or other beverages for the perfect, anytime protein boost.

Soy protein is derived from soybeans, which have been a dietary staple and primary source of high-quality protein for people throughout the world for centuries. Soy is considered a complete protein because it contains essential and nonessential amino acids necessary for human nutrition. It’s also a good source of fiber, calcium and vitamin E.

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Benefits of soy protein

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