The Potential Effects of Phytoestrogens: The Role in Neuroprotection

Abstract

Phytoestrogens are naturally occurring non-steroidal phenolic plant compounds. Their structure is similar to 17-β-estradiol, the main female sex hormone. This review offers a concise summary of the current literature on several potential health benefits of phytoestrogens, mainly their neuroprotective effect. Phytoestrogens lower the risk of menopausal symptoms and osteoporosis, as well as cardiovascular disease. They also reduce the risk of brain disease. The effects of phytoestrogens and their derivatives on cancer are mainly due to the inhibition of estrogen synthesis and metabolism, leading to antiangiogenic, antimetastatic, and epigenetic effects. The brain controls the secretion of estrogen (hypothalamus-pituitary-gonads axis). However, it has not been unequivocally established whether estrogen therapy has a neuroprotective effect on brain function. The neuroprotective effects of phytoestrogens seem to be related to both their antioxidant properties and interaction with the estrogen receptor. The possible effects of phytoestrogens on the thyroid cause some concern; nevertheless, generally, no serious side effects have been reported, and these compounds can be recommended as health-promoting food components or supplements.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

“…Cardiovascular risk factors include family history, age, smoking, alcohol, stress, and the excessive consumption of sugars and saturated fatty acids that cause obesity and dyslipidemia. In particular, trans fats increase total cholesterol and low-density lipoprotein (LDL) cholesterol levels; consequently, it is recommended that the consumption of meat, sugary snacks, ice cream, and fast food be reduced [103,104]. In contrast, vegetables and fruits, whole grains (brown rice and mixed grains), and legumes provide a variety of complex carbohydrates, fiber, potassium, vitamins, and antioxidants to lower blood pressure and improve sugar and lipid metabolism [105].…”

Phytoestrogens (Resveratrol and Equol) for Estrogen-Deficient Skin—Controversies/Misinformation versus Anti-Aging In Vitro and Clinical Evidence via Nutraceutical-Cosmetics

“…Although not the focus of this review, the phytoestrogens mentioned in this section have many attributes, including antioxidant, anti-inflammatory, anti-bacterial, antifungal, anti-viral, anti-hypertensive, anti-convulsant and have demonstrated promising effects in the prevention of various ailments, such as heart disease, cancer, stroke, diabetes, obesity, osteoporosis, many neurodegenerative disorders such as Alzheimer's disease [8][9][10]44,45,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] and finally age-related decline in human skin health [8][9][10], which will be covered in detail in the latter sections.…”

“…Food safety has been addressed recently in vegetarian diets [67], where soy, soy foods and phytoestrogens were examined along with concerns about infant nutrition/development, pro-cancer disorders, thyroid disturbances, sex hormone perturbations and altered reproductive functions [65,67]. The health effects of soy/phytoestrogens have been investigated for more than 30 years, with more than 2000 peer-reviewed articles published annually on this topic, including reviews on each health controversy mentioned above [9,44,45,47,[52][53][54][59][60][61][62][63][64][65][66][67][68][69][70]. However, in brief, each of the four major health controversies is addressed below.…”

“…No. Scientific evidence is accumulating to suggest that soy/phytoestrogens may have a role in preventing chronic disease, and breast and prostate cancers [52,59,61,64,68,[71][72][73][74][75][76][77]. The strategic director (Dr. McCullough) of nutritional epidemiology for the American Cancer Society (USA) recently stated, "So far, the evidence does not point to any dangers form eating soy (phytoestrogens) in people, and the health benefits appear to outweigh any potential risk.…”

“…From 1980 to 2000, approximately one hundred cumulative reports were published; however, to date, over 2000 journal articles on equol have been reported [109,114]. Both resveratrol and equol have applications to improve health and prevent/treat disease [45,47,[52][53][54]58,59,61,64,66,[71][72][73][74][75][76][77]109,110,113,114,118]; however, this review is focused on skin applications in estrogen-deficient skin.…”