The Health Merits of Isoflavones in Food Applications

September 15, 2003

12 Min Read
The Health Merits of Isoflavones in Food Applications

The Health Merits of Isoflavones in Food Applications

by Susan Colebank

Isoflavones and their health benefits have been talked about for years in the natural products community. Isoflavone supplements hit store shelves years ago, in the hopes that a concentrated dose of these constituents would pack a healthy punch. On the food and beverage side, manufacturers have been familiar with soyfoods, soymilk and soy flour. But what does the landscape of isoflavones and food application look like? While food manufacturers have been wary about using concentrated isoflavones, they have been very receptive to the idea of boosting the health quotient of a food or beverage with an ingredient that doesnt take up a lot of room in the end product, yet offers all healthy parts of the soybean, including isoflavones.

Isoflavones are a class of phytoestrogens found predominantly in legumes (other classes include lignans and coumestans). Soy isoflavones are heterocyclic phenols that are structurally similar to estradiol-17-beta and selective estrogen receptor modulators.

Isoflavones come in all shapes, sizes and potencies. Soy isoflavones include genistein, daidzein, daidzin, gylcitin and glycetein. Soy, however, isnt the only botanical with isoflavone benefits: red clover isoflavones include daidzein and genistein, as well as biochanin A, and black cohosh isoflavones include formononetin. (For more on red clovers isoflavones, see below.)

Soy isoflavones occur as conjugates such as beta-glucosidases, acetyl glucosidases and malonyl glucosidases. After being consumed, the isoflavone undergoes a conversion in which the sugar molecule is removed and turned into into metabolically active aglycons. Following this conversion, one third of the aglycon is absorbed as free isoflavone, while the rest are changed into isoflavone metabolites that are then absorbed.

Human gut microflora have been shown to exert metabolic activities on isoflavones, which influences bioavailability and bioactivity.1 Absorption of isoflavones is likely to occur in the small intestine where there is a diverse range of microfloral species able to hydrolyze conjugated isoflavones, releasing the bioactive aglycone for absorption or further metabolism and reconjugation. The identification of gut microbes that metabolize isoflavone aglycones is not well established, New Zealand researchers reported. Such information may lead to a better understanding of the bioavailability of isoflavones in functional foods.

The Health Benefits

Isoflavones of the soy variety have been shown to have varying degrees of benefit on such conditions as hot flashes, cognition, heart health, bone mass and cancer.

Isoflavones have both hormonal and nonhormonal properties, according to researchers out of Loma Linda Universtiy, California. The estrogen-like effects of isoflavones in combination with the low reported frequency of hot flushes in Japan has prompted investigation of the effect of soy on menopausal symptoms, they reported.2 In their review of 19 trials involving more than 1,700 women, available data appears to justify the recommendation that menopausal women with frequent hot flashes consider trying soyfoods or isoflavone supplements to alleviate symptoms.

Isoflavones may also be linked with cognitive improvement, especially in memory and logic.3 In a double blind, parallel study, 33 postmenopausal women not receiving conventional hormone replacement therapy (HRT) received either a soy supplement (totaling 60 mg/d of isoflavone equivalents) or a placebo for 12 weeks. Those receiving the isoflavone supplement showed significantly greater improvements in recall of pictures and in a sustained attention task. The groups did not differ in their ability to learn rules, but the isoflavone supplement group showed significantly greater improvements in learning rule reversals. They also showed significantly greater improvement in a planning task.

In other menopausal health research, controversy exists about the ability of soy protein and isoflavones to modulate vascular reactivity and biochemical cardiovascular disease risk markers in healthy, normolipidemic women. Researchers at the University of California, Davis, conducted a randomized, double blind, crossover study consisting of 28 women consuming 25 g/d of three protein products (isolated soy protein with 107 mg of isoflavones, ethanol-washed isolated soy protein with 2 mg of isoflavones and total milk protein).4 Postocclusion peak flow velocity of the brachial artery was significantly lowered after treatment with isolated soy protein with isoflavones, which is consistent with a vasodilatory response, according to the researchers. Daily consumption of soy protein with isoflavones can result in positive vascular effects that are independent of lipid and antioxidant effects in healthy postmenopausal women, they concluded.

Bone health is another area that has been shown to benefit from isoflavones. In particular, daidzein and genistein have appeared to benefit bone-nodule formation in rat calvaria osteoblasts in vitro.5 Researchers out of China reported genistein can stimulate bone-nodule formation via the estrogen-receptor-dependent pathway, while daidzein also stimulates bone-nodule formation and increases the release of osteocalcin, although it is not mediated by the estrogen-receptor-dependent pathway. And, in a review of recent literature, the effects of isoflavones have been studied to determine whether genistein and daidzein may prevent or treat osteoporosis.6 In evidence gathered from animal models, in vitro experiments and epidemiological reports, it seems isoflavones may have skeletal benefits in women with little or no ovarian estrogen production.

In the realm of cancer, the development of endometrial cancer is largely related to prolonged exposure to unopposed estrogens. Phytoestrogens, which may have antiestrogenic effects, may prevent such cancers.7 In a case-control study, dietary information was collected from women aged 35 to 79 years who were diagnosed with endometrial cancer. It was found that isoflavone and lignan consumption were inversely related to the risk of endometrial cancer, with significant associations seen in postmenopausal women.

Soy isoflavones may also reduce the risk of prostate cancer. In a case-control study conducted in China, it was indicated that intakes of both soyfoods and the isoflavones genistein and daidzein reduced the incidence of prostate cancer.8

Applications in Foods & Beverages

Although soys isoflavones have a wealth of science behind them, a manufacturer shouldnt ignore the fact that it is the soys protein that got the heart health claim from the Food and Drug Administration (FDA). However, that doesnt mean the two constituents cant go hand in hand in a food or beverage application. For heart health, soy protein with or without soy isoflavones is recognized as having beneficial effects, said Brent Flickinger, Ph.D., nutrition research scientist from Decatur, Ill.-based ADM. On the other hand, current research suggests that soy isoflavones, without soy protein, would be an appropriate formula for a bone health product.

Soy protein does not offer all of the benefits received from a soyfood. According to Walter Wilms, food sales manager of the North American Health Division of Minneapolisbased Acatris, manufacturers need to keep in mind that a soy protein isolate or concentrate has most of its nutrients washed away or destroyed during the processing. And, a typical soy protein isolate has only 1 mg to 3 mg of isoflavones per gram of protein isolate. If you want a large amount of soy protein in a food application in bread or cereal that carries the soy protein health claim, manufacturers use a soy protein isolate and then use a gram or two of SoyLife to bring up isoflavone levels, said Wilms, whose company produces Soylife Focus, derived from the germ of the soybean, for food and beverage applications and that has no less than 15 mg of isoflavones per gram. One to two percent of the total food application is SoyLife, which leads to minimum or no impact being imparted on flavor or texture of the food application.

Manufacturers can also choose to use a soy ingredient that has its protein intact but with a beefed-up isoflavone content. Some companies are interested in combining soy protein and concentrated isoflavones to come up with the desired profile they want for the product and its health effects, said Lee Covert, director of business development at the St. Louis-based Solae Co., which offers soy protein with naturally occurring isoflavones and concentrated isoflavones. (Solae offers SuproSoy, Alpha and Prevastein brands of soy ingredients.) We believe it is important to offer a range of products to manufacturers and consumers. Weve sponsored the majority of research on the health effects of soy protein, and a great deal of quoted isoflavone research is extrapolated from those studies.

According to Wilms, manufacturers interested in soy for food applications look for products that reflect the Asian diet, which has proven beneficial for many health conditions. Although there is no RDA (recommended daily allowance) for isoflavones, the typical Asian diet is between 20 mg/d and 50 mg/d of isoflavones, according to Wilms, who added that it makes sense health-wise and marketing-wise to include isoflavones between those levels.

Bill Fenske, vice president of technical services at Hope, Minn.-based Sunrich, added that if it aint broke, dont fix itthat is, dont mess with nature and the isoflavone-to-protein ratio. We take the route that we use the content that is naturally found in the whole soyfood, he said.

According to Lee Knudson, product manager for Minneapolis-based Cargills isoflavone and chondroitin businesses, With isoflavones, we first need to understand the science behind them and how to apply it. Theres one constituent that has created a significant amount of interestequol, a metabolite from daidzein. The current research indicates that about half of the population, possibly because of diet or genetic make-up, is really good at metabolizing daidzein and equol, and the other half are not. Scientists think that equol may be a key constituent for isoflavones health benefits.

According to Wilms, research is showing that the real benefit of soy is not by having just one isolated component but rather having all the parts that make up soyisoflavones, omega-3s, protein and vitamin E together. He added, though, that the No. 1 manufacturing concern to keep in mind when using soy in a food application is taste. You really dont want any sort of change in your food applicationyou just want to enhance it with healthier ingredients, he said.

With soy, you have to use the right complementary flavors, according to Fenske. If you get to a high enough level, isoflavones impart a bitter taste, he said. A lot of people use masking flavor like propylene glycol to deaden the taste buds. Malt and nutty flavors go well with soy.

Fenske added that different growing conditions can affect the isoflavone content in different soybeans, such as climate and stress. So much so, it can vary from county to county, as well as from variety to variety.

Besides taste issues, another important consideration to keep in mind when choosing an isoflavone-containing soy ingredient is if it has GRAS (generally recognized as safe) status, according to Flickinger.

The soy-using food sectorwhich includes baked goods, nutrition bars and cerealshas been well-served by the soy ingredient industry. However, the beverage sector is starting to see a renewed interest in incorporating soy into beveragesbeyond just soymilk. Wilms stated consumers are turning to soy-containing products not only for specific health benefits, but also for overall health in general. I think the selling point is creating a product that is healthy and tastes good, he said.

Knudson said, Weve seen quite a bit of interest from manufacturers wanting to use soy in beverages. Women-oriented beverages are the primary area of interest, especially in terms of bone health.

In fact, Cargill found through market research that women wanted something small and convenient that they could take with them; they wanted something that provided significant health benefits; and they wanted it to be low-cal. On the manufacturer front, Cargill was looking for something that was easy to manufacture and that conveyed health benefits to the end consumer for its clients.

With all of this marketing data at a potential manufacturers fingertips, whats the next step? We provide assistance to our customers by having a food or beverage prototype work in a commercial setting, said Knudson, whose company makes AdvantaSoy Clear, one of multiple grades of soy isoflavone products marketed by Cargill. Its through our trial and error, and not theirs, that we find a product that works for them.

According to Covert, food manufacturers continue to struggle with whether the added cost of a higher isoflavone level product is worth putting in a food product, when there are competitive products making similar claims with lower costs. However, the natural products channel still has the consumer interest in health-promoting products, and these consumers are willing to pay for added value if they understand it and the product really delivers, he said.

For a list of references to this story, click here.

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