Standardized Soy Isoflavones by Nature's Way

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Androgenic alopecia. Topical red clover has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in individuals with androgenic alopecia shows that topical application of a combination of red clover flower extract and acetyl tetrapeptide-3 increases the growth phase of hair production by 13% and decreases the resting phase of hair production by 29% when compared to baseline (19540). The validity of these findings is limited by the lack of a comparator group.
• Benign prostatic hyperplasia (BPH). Although there is interest in using oral red clover for BPH, there is insufficient reliable information about the clinical effects of red clover for this condition.
• Breast cancer-related hot flashes. It is unclear if oral red clover is beneficial for reducing hot flashes in patients who have had breast cancer. Details: A small clinical study in breast cancer patients with menopausal symptoms due to tamoxifen therapy shows that taking red clover extract (Promensil Forte) 80 mg daily for 24 months does not reduce menopausal symptoms, including hot flashes, sleep disturbance, and fatigue, any more than placebo (102901).
• Hyperlipidemia. It is unclear if oral red clover is beneficial in patients with hyperlipidemia; research is conflicting. Details: Most clinical trials in adult females with or without elevated cholesterol levels show that taking red clover extracts providing isoflavones 40-120 mg daily for 3 months to 1 year does not reduce total or low-density lipoprotein (LDL) cholesterol, or increase high-density lipoprotein (HDL) cholesterol, when compared with control (3375,8502,11089,11091,17091,19450,19543). However, a meta-analysis of 10 clinical trials in perimenopausal and postmenopausal patients with or without hyperlipidemia shows that red clover decreases total cholesterol by around 11 mg/dL, but does not affect LDL cholesterol, triglyceride, or HDL cholesterol levels, when compared with placebo (102840). This finding is limited by imprecision and inconsistency of the results and the fact that the benefit seems to be mostly attributed to two trials with a high risk of detection and performance bias. When this meta-analysis was repeated without those two trials, red clover supplementation for at least three months still shows a significant, albeit smaller, reduction in total cholesterol of around 4 mg/dL when compared with placebo among post-menopausal individuals. The meta-analysis also shows a small but statistically significant increase in HDL by approximately 1.5 mg/dL and no change in LDL or triglyceride levels (112145). Included studies were of moderate to high quality and lacked heterogeneity.
• Mastalgia. It is unclear if oral red clover is beneficial in patients with mastalgia. Details: One very small study in patients with cyclic mastalgia shows that taking red clover isoflavones (Promensil, Novogen) 40-80 mg daily reduces subjective ratings of breast pain and tenderness. Reductions in pain were 44% with 40 mg and 31% with 80 mg, compared with 13% for placebo (9552).
• Menopausal symptoms. It is unclear if oral red clover is beneficial for menopausal symptoms; research is conflicting and has notable methodological issues. Details: The most recent meta-analysis of 8 small clinical trials in patients with menopausal symptoms suggests that red clover reduces hot flash frequency by an average of 1.7 times when compared with control. The benefit tends to be greater in those with a higher frequency of hot flashes at baseline (5 or more) and when higher doses of red clover isoflavones are used (80 mg or more daily) (105694). However, this finding is limited by imprecision and inconsistency, as well as selective reporting bias in some of the included trials. An older meta-analysis of small, low-quality clinical studies in menopausal patients also suggests that red clover might improve psychological symptoms such as anxiety and depression when compared with control (91525). The most extensively studied product is a specific red clover supplement (Promensil or Melbrosin, Novogen). A meta-analysis of 5 small clinical studies assessing only Promensil shows that taking 80 mg daily for 12 weeks reduces hot flash frequency by 30% to 50%, or by about 3-4 hot flashes per day, when compared with placebo (96731). The validity of these findings is limited by imprecision, inconsistency, and publication bias. Notably, this meta-analysis and all included studies were funded by the supplement manufacturer (8925,10976,10991,17103,19545,96731). In contrast, studies with independent funding sources have not found a benefit with red clover isoflavones 40-120 mg daily for up to 12 months when compared with placebo (10975,17091,19549). Some research has also found benefit for menopausal symptoms when red clover is used in combination with other ingredients. Red clover has been used in combination with black cohosh, dong quai, milk thistle, American ginseng, and Vitex agnus-castus (Phyto-Female Complex) twice daily for 3 months (19552). Red clover isoflavones 37.1 mg have also been used in combination with a probiotic-rich liquid daily for 12 weeks (96730).
• Osteoarthritis. It is unclear if topical red clover is beneficial in patients with osteoarthritis. Details: Preliminary clinical research shows that applying 20 drops of a standardized extract of red clover aerial parts to the knee twice daily for 4 weeks, in addition to taking meloxicam orally, improves subjective measures of pain and function more than using meloxicam plus placebo. However, radiological and laboratory changes were not evaluated (102839).
• Osteoporosis. It is unclear if oral red clover is beneficial in patients with osteoporosis; research is conflicting. Details: One small clinical study in healthy postmenopausal patients shows that taking red clover providing isoflavones 57-85.5 mg daily for 6 months increases bone mineral density (BMD) of the proximal radius and ulna by 3% to 4% (10948). Another clinical study in females ages 49-65 years shows that taking a specific red clover extract (Promensil, Novogen) providing isoflavones 40 mg daily for one year does not increase BMD or bone mineral content (BMC) of the hip, but seems to slightly reduce the loss of lumbar spine BMD and BMC when compared with placebo (6127). However, other research has found no benefit. One clinical study in patients who are at least one year post-menopause and not taking bone preserving medications shows that taking a specific product containing enriched red clover isoflavones (Rimostil [formononetin enriched], Novagen) 50 mg daily for 2 years does not improve BMD of the spine, femoral neck, distal radius, or proximal radius when compared with placebo. However, this study may have been underpowered due to a high drop-out rate (91524). Another small clinical study in perimenopausal and postmenopausal adults shows that taking red clover flowering tops providing isoflavones 120 mg daily for one year does not seem to slow the loss of hip, femoral neck, or lumbar spine BMD when compared with placebo (17091). More evidence is needed to rate red clover for these uses.

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LIKELY SAFE ...when used orally in amounts commonly used in foods. Red clover has Generally Recognized As Safe (GRAS) status for use in foods in the US (4912,10372).

POSSIBLY SAFE ...when used orally and appropriately in supplemental amounts. Red clover extracts containing up to 80 mg isoflavones have been used with apparent safety in clinical studies lasting up to 2 years (3375,6127,8925,11089,11091,17091,19540,19556,91524,102901,102840). ...when used topically and appropriately. Red clover extracts have been used topically with apparent safety for up to 4 weeks (102839).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts commonly found in foods (4912).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in medicinal amounts. Red clover has estrogenic activity (19555); avoid using. There is insufficient reliable information available about the safety of the topical use of red clover during pregnancy and lactation.

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ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = B Although some laboratory research suggests that red clover may have anticoagulant and antiplatelet activity, clinical research has not shown this effect.  Details In vitro research suggests that genistein in red clover has antiplatelet effects, and historically, red clover was thought to have anticoagulant effects due to its coumarin content. However, some experts state that this is unlikely as most natural coumarins have not been shown to have anticoagulant effects, and their content in red clover is low (17091,19557,19558,19559). Additionally, some clinical research in postmenopausal patients found no effect on coagulation or prothrombin time with the use of red clover flowering tops 378 mg daily for 12 months or red clover isoflavone (Rimostil) 50 mg daily for 2 years (17091,91524).

CAFFEINE Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, soy might reduce the clearance of caffeine; however, a small clinical study found no effect.  Details Red clover contains genistein. Taking genistein 1 gram daily for 14 days seems to inhibit caffeine clearance and metabolism in healthy females (23582). However, this effect does not seem to occur with the lower amounts of genistein found in red clover. A clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of caffeine (105693).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, red clover might increase levels of drugs metabolized by CYP1A2; however, a small clinical study found no effect.  Details In vitro evidence shows that red clover inhibits CYP1A2 (12479). However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of caffeine, a CYP1A2 probe substrate (105693).

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, red clover might increase the levels and clinical effects of drugs metabolized by CYP2C19.  Details In vitro evidence suggests that red clover weakly inhibits CYP2C19 (12479). This interaction has not been reported in humans.

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, red clover might increase levels of drugs metabolized by CYP2C9; however, a small clinical study found no effect.  Details In vitro evidence suggests that red clover might inhibit CYP2C9 (12479). However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of tolbutamide, a CYP2C9 probe substrate (105693).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Unlikely •  Level of Evidence = B Theoretically, red clover might increase levels of drugs metabolized by CYP3A4; however, a small clinical study found no effect.  Details In vitro evidence shows that red clover might inhibit CYP3A4 isoenzymes (6450,12479). However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of alprazolam, a CYP3A4 probe substrate (105693).

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use of large amounts of red clover might interfere with estrogen therapy.  Details Red clover contains phytoestrogens which might have estrogenic activity in some people. Theoretically, red clover might compete for estrogen receptors and interfere with estrogen-containing drug therapy (4743,19560,19729).

METHOTREXATE (Trexall, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, red clover might increase the risk of methotrexate toxicity.  Details In a case report, a 52-year-old female receiving weekly methotrexate injections for psoriasis developed symptoms of methotrexate toxicity, including severe vomiting and epigastric pain, after three days of taking red clover 430 mg daily. Toxicity resolved after red clover was discontinued. However, no liver function tests or methotrexate levels were reported (91522).

TAMOXIFEN (Nolvadex) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, the phytoestrogens in red clover might interfere with tamoxifen.  Details In vitro and animal research suggests that genistein, a constituent of red clover, might antagonize the antitumor effects of tamoxifen (8192). However, there is some evidence from an animal study that red clover does not reduce the efficacy of tamoxifen (102901). Until more is known, tell patients taking tamoxifen to avoid red clover.

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General ...Orally and topically, red clover seems to be well tolerated.
Most Common Adverse Effects:
Orally: Myalgia, nausea, and vaginal spotting.

Dermatologic ...Orally, a specific red clover isoflavone product (Promensil) has been associated with mild cases of psoriasis and thrush, although a direct causal link has not been established (9552).

Gastrointestinal ...Orally, red clover has been reported to cause nausea (8194).

Genitourinary ...In human research, 80 mg, but not 40 mg, of a specific red clover isoflavone product (Promensil) increased the duration of menstrual cycles in patients with mastalgia (9552). Red clover has also been reported to cause vaginal spotting (8194).

Hematologic ...In one case report, a 53-year-old female had a spontaneous subarachnoid hemorrhage associated with the use of an herbal supplement containing red clover, dong quai, and eleuthero. It is not clear if this was due to red clover, another ingredient, the combination of ingredients, or other factors (70419). In another case report, a 55-year-old female with protein S deficiency and systemic lupus erythematosus (SLE) had temporary vision loss in the left eye from hemiretinal vein thrombosis 3 days after taking a combination phytoestrogen product containing red clover 250 mg, wild yam 276 mg, dong quai 100 mg, and black cohosh 250 mg (13155). It is unclear if red clover contributed to this event.

Musculoskeletal ...Orally, red clover has been reported to cause myalgia (8194).

Neurologic/CNS ...Orally, a specific red clover isoflavone product (Medoflavon) has been associated with headache, although with a similar frequency to placebo (19545).

Oncologic ...Due to potential estrogenic effects of red clover isoflavones, there has been some concern that red clover might increase the risk of estrogen-sensitive cancers such as breast cancer or uterine cancer. A meta-analysis of 8 clinical trials suggests that increased intake of red clover- and soy-derived isoflavones may modestly increase mammographic breast density in premenopausal, but not postmenopausal, adults when compared with placebo. However, in a sub-group analysis assessing only isolated red clover isoflavones, there was no change in breast density (70428). Furthermore, a 2015 review by the European Food Safety Authority (EFSA) reported no increase in risk of breast cancer in females taking isoflavone-containing supplements (91725). Similarly, no effect was found on endometrial thickness and histopathological changes in the uterus after up to 36 months of supplementation with 40-120 mg daily of isoflavones from red clover extract (91725).

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