**6. Soy and OA**

The main soy isoflavones include genistein, daidzein, and glycetine [84]. Genistein is structurally similar to ipriflavone [84], a synthetic isoflavone. SERMs such as tamoxifen [85] and ipriflavone [86] have both been shown to influence cartilage metabolism and reduce or alleviate the symptoms associated with OA. Therefore, it is conceivable to also expect that genistein similarly influences cartilage metabolism.

Our *in vitro* study [87] found that genistein had the capacity to reduce inflammation in human chondrocytes. Indeed, in chondrocytes treated with LPS to induce inflammation, genistein significantly decreased COX-2 production (**Figure 6**), but

#### **Figure 6.**

*COX-2 levels in cytosolic fraction of chondrocytes. LPS, lipopolysaccharides; and GEN, genistein. Bars represent mean ± SE, n = 3 per treatment group. Bars with different letters are significantly different from each other (P < 0.05).*

#### **Figure 7.**

*COX-1 levels in cytosolic fraction of chondrocytes. LPS, lipopolysaccharides; and GEN, genistein. Bars represent mean ± SE, n = 3 per treatment group.*

did not have an effect on COX-1 production (**Figure 7**) [87]. This is of particular interest, as NSAIDs are thought to inhibit inflammation via COX-1 and COX-2 dependent pathways, but are thought to cause damage because of the inhibition of COX-1, an important enzyme that regulates normal cellular processes and is expressed in most tissues [88]. This inhibited synthesis caused by most NSAIDS can negatively affect the maintenance and integrity of the gastric and duodenal mucosa, as well as lead to kidney issues [89, 90]. COX-2, however, is generally unexpressed by most tissues and is upregulated specifically by inflammation [91]. The seemingly selective inhibition of COX-2 by genistein provides a promising alternative to those who experience gastric distress due to the use of NSAIDs.

IL-1β, an inflammatory cytokine, was also measured in this study and was found to be lower in both the high and low doses of genistein (**Figure 8**) [87]. More importantly, YKL-40, a marker of human cartilage glycoprotein degradation [92], was found to be suppressed in genistein treated groups (**Figure 9**); however, the difference between the LPS and genistein groups did not reach statistical significance [87].

An animal study by Borzan et al. [93] also supports our clinical findings on soy. The aim of the aforementioned study was to determine if a soy diet could reduce the pain behaviors and inflammation induced by the intraplantar administration of complete Freund's adjuvant. They reported that neuropathic pain following partial sciatic nerve injury was attenuated in rats fed a soy protein diet [93], indicating that soy may be effective in attenuating pain symptoms, including those of OA.

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*Evidence for the Effectiveness of Soy in Aging and Improving Quality of Life*

Lymphocytes and monocytes are often seen at sites of injury and inflammation [51]. Our lab investigated the effect of soy isoflavone supplementation on ovariectomy induced lymphopoiesis in rats. In this animal study [94], we observed that ovariectomy-induced increases in peripheral blood total lymphocyte and monocyte counts were returned to the levels of sham-operated rats after soy isoflavone supplementation (**Figure 10A** and **B**). Forty-eight 12-month-old Sprague-Dawley rats were either sham-operated (sham; 1 group) or OVX (3 groups) and were fed a standard semi-purified diet for 120 days. Thereafter, the OVX groups received one of the three doses of isoflavones: 0 (OVX), 500 (ISO500), or 1000 (ISO1000) mg/kg diet for 100 days. Ovariectomy significantly (*P* < 0.05) increased the total leukocyte, lymphocyte, monocyte, eosinophil, and basophil counts. Isoflavones at 500 and 1000 mg/kg diet returned the total leukocyte counts as well as leukocyte subpopulations to levels comparable to that of sham. These findings indicate that isoflavones are capable of normalizing circulating levels of inflammatory cells that produce many proinflammatory mediators, which may prove effective for the synovial joint. Our lab also carried out a three-month double-blind randomized clinical trial [95] to investigate the effects of soy supplementation on symptoms associated with knee OA. About 135 free-living individuals (64 men, mean age = 55.8 ± 13.6 years; and 71 women, mean age = 59.3 ± 12.0 years) with knee OA were randomly assigned to receive 40 g of either soy protein or milk protein daily. This study indicated that soy protein regimen containing 88 mg isoflavones improved (*P* < 0.05) knee range of motion and ability to climb several flights of stairs, and reduced (*P* < 0.05) the intensity, frequency, severity of pain, hindrance to activities (**Figure 11A**), and use of pain medications (**Figure 11B**). The improvement in self-described pain parameters

*YKL-40 level in culture supernatant which was measured via ELISA kit. LPS, lipopolysaccharides; and GEN,* 

*IL-1β level in culture supernatant measured via ELISA kit. LPS, lipopolysaccharides; and GEN, genistein. Bars* 

*DOI: http://dx.doi.org/10.5772/intechopen.85664*

*represent mean ± SE, n = 4 per treatment group.*

*genistein. Bars represent mean ± SE, n = 4 per treatment group.*

**Figure 8.**

**Figure 9.**

*Evidence for the Effectiveness of Soy in Aging and Improving Quality of Life DOI: http://dx.doi.org/10.5772/intechopen.85664*

#### **Figure 8.**

*IL-1β level in culture supernatant measured via ELISA kit. LPS, lipopolysaccharides; and GEN, genistein. Bars represent mean ± SE, n = 4 per treatment group.*

#### **Figure 9.**

*YKL-40 level in culture supernatant which was measured via ELISA kit. LPS, lipopolysaccharides; and GEN, genistein. Bars represent mean ± SE, n = 4 per treatment group.*

Lymphocytes and monocytes are often seen at sites of injury and inflammation [51]. Our lab investigated the effect of soy isoflavone supplementation on ovariectomy induced lymphopoiesis in rats. In this animal study [94], we observed that ovariectomy-induced increases in peripheral blood total lymphocyte and monocyte counts were returned to the levels of sham-operated rats after soy isoflavone supplementation (**Figure 10A** and **B**). Forty-eight 12-month-old Sprague-Dawley rats were either sham-operated (sham; 1 group) or OVX (3 groups) and were fed a standard semi-purified diet for 120 days. Thereafter, the OVX groups received one of the three doses of isoflavones: 0 (OVX), 500 (ISO500), or 1000 (ISO1000) mg/kg diet for 100 days. Ovariectomy significantly (*P* < 0.05) increased the total leukocyte, lymphocyte, monocyte, eosinophil, and basophil counts. Isoflavones at 500 and 1000 mg/kg diet returned the total leukocyte counts as well as leukocyte subpopulations to levels comparable to that of sham. These findings indicate that isoflavones are capable of normalizing circulating levels of inflammatory cells that produce many proinflammatory mediators, which may prove effective for the synovial joint.

Our lab also carried out a three-month double-blind randomized clinical trial [95] to investigate the effects of soy supplementation on symptoms associated with knee OA. About 135 free-living individuals (64 men, mean age = 55.8 ± 13.6 years; and 71 women, mean age = 59.3 ± 12.0 years) with knee OA were randomly assigned to receive 40 g of either soy protein or milk protein daily. This study indicated that soy protein regimen containing 88 mg isoflavones improved (*P* < 0.05) knee range of motion and ability to climb several flights of stairs, and reduced (*P* < 0.05) the intensity, frequency, severity of pain, hindrance to activities (**Figure 11A**), and use of pain medications (**Figure 11B**). The improvement in self-described pain parameters

**Figure 10.**

*(A and B) Indicate effects of isoflavones (ISO) on lymphocyte and monocyte counts. Values are mean ± SE (n = 12). Bars that do not share the same superscript are significantly different (P < 0.05).*

**Figure 11.**

*(A) represents self-reported pain limiting physical activities with scores ranging from 1 to 2; (1) referring to no limitation and (2) referring to pain as causing limitation in physical activity. (B) indicates the use of pain medications (mean + SE). A lower score reflects less use of pain medication and a higher score reflects more frequent use of pain medication.*

due to soy supplementation became more pronounced as the treatment duration progressed. Additionally, the soy regimen significantly improved circulating levels of IGF-I which suggests that isoflavones may exert anabolic effects on the cartilage.

In the same study, serum IGF-I as well as human cartilage glycoprotein 39 (YKL-40), a marker of joint destruction [92], were assessed. Results indicated that protein supplementation had significantly lowered mean serum concentration of YKL-40 in men, implying that soy can slow down cartilage degradation. Although both proteins, as expected, increased (*P* < 0.05) circulating levels of IGF-I, soy protein had a more pronounced effect compared to milk protein. We have repeatedly shown [84, 96] that soy has the ability to uniquely enhance serum IGF-I in comparison with milk protein, indicating that this effect may be due to its isoflavone content rather than merely protein.

The findings of our three-month study indicate that soy protein supplementation significantly reduced the intensity and frequency of pain. By comparison, milk protein only reduced pain intensity indicating that the reduction in the frequency of pain and discomfort are specific to soy and not the control protein. Our findings also indicate a reduced need for pain medication. The increased serum IGF-I level with soy supplementation suggests that isoflavones may exert anabolic effects on the cartilage, and decreased YKL-40 levels which is associated with cartilage degeneration, support our hypothesis that soy can improve symptoms and severity of OA. The authors suggest that people with no contraindications to soy isoflavones use ipriflavone, a synthetic isoflavone, for decreasing the symptoms of OA. However, this is just a suggestion and further research must be done to assess the potency of isoflavone usage for symptomatic control of OA.

**35**

*Evidence for the Effectiveness of Soy in Aging and Improving Quality of Life*

study group, compared to the control of regular soymilk.

tant since CVD remains the leading cause of death in the US.

As mentioned previously, soy isoflavones are phytoestrogens. Estrogen is known

Soy can be beneficial in many forms beyond that of soymilk. A study [99] that supplemented whole soy foods (3–4 servings per day) for 12 weeks found that the soy intervention significantly reduced total cholesterol, LDL-C, non-HDL cholesterol, and apoB even though BMI did not decrease. An earlier study [100] also found that soy protein supplementation resulted in decreased cholesterol levels. Prehypertensive women who supplemented 40 g of soy flour saw decreases in LDL-C and well as high sensitivity C-Reactive Protein (CRP), a marker of inflammation [101]. Interestingly, another study found that 1 month of soy nut supplementation modestly reduced arterial stiffness but did not improve inflammatory biomarkers [102]. Additionally, Lucas et al. [103] found that soy isoflavones prevented both hyperlipidemia and atherosclerotic lesions in ovariectomized Golden

While there are still gaps in the research for CVD and soy consumption, research generally points to a positive effect of soy on heart health, irrespective to its effect on cholesterol. Finding that soy significantly decreased the development of atherosclerotic lesion in a hamster model of postmenopausal CVD is particularly impor-

Just as OA greatly affects women more so than men, osteoporosis is a particularly concerning problem for the aging female population. Because intestinal cells contain ER, and because estrogen enhances calcium transport [104], it stands to reason that phytoestrogens like soy may increase intestinal calcium transport. There have been multiple studies researching intestinal transport of calcium and soy, as well as the effect of soy on animal models of osteoporosis, and human studies. A study by our lab in 2001 [104] confirmed that not only does ovariectomy decrease rates of calcium transport, but that soy isoflavones in soy protein promoted calcium absorption in a manner analogous to estrogen without any of the side effects/risk. Pawlowski et al. [105] also found that soy isoflavones were effective in increasing calcium retention in bone, and Arjmandi et al. [84] found that women not on hormone replacement therapy who supplemented soy protein experienced reduced

Animal studies have yielded positive results for isoflavone's bone sparing properties. A 1998 study [106] by our lab compared casein protein and soy protein in ovariectomized (OVX) rats, and found that soy protein with higher levels of isoflavones spared the femoral bone density decreases brought about by ovariectomy. Our 2006 study [107] found that soy positively affected tibial architectural properties of OVX rats, including trabecular thickness, separation, and number

to be cardioprotective, so it stands to reason that soy may also be cardioprotective. Many of the clinical trials investigating the effect of soy supplementation on heart health focus mainly on cholesterol levels. This may be due to the fact that the phytosterols, like those found in soy, compete with cholesterol for intestinal absorption [97]. A 2015 study [98] investigated the effect of 8 weeks of standard soymilk supplementation against the effect of 2 g/day of phytosterols and 10 g/day of inulin-enriched soymilk supplementation. While both groups did see a reduction in LDL-C in both groups, the study group supplementing with the extra phytosterols and inulin saw significantly better results. TC was also significantly reduced in the

*DOI: http://dx.doi.org/10.5772/intechopen.85664*

**7. Soy and cardiovascular disease**

Syrian Hamsters.

**8. Soy and osteoporosis**

urinary calcium excretion.
