What are Phytoestrogens?
Phytoestrogens are estrogen hormone-like chemicals found in plants. Examples of phytoestrogens are isoflavones (genistein, daidzein), flavones, coumestans and lignans. What makes this group of estrogen-like chemicals of medical and nutritional interest is that their chemical structure is similar to estrogen.
Consumption of phytoestrogen rich diet, depending on the phytoestrogen concentration in the diet and concentration of sex hormones in the body, life stage and gender, can have estrogenic effects (have the same effects as estrogen) or anti-estrogenic effects (inhibit or suppress the effects of estrogen).
What Are the Benefits of Phytoestrogens?
Several studies found positive association between intake of phytoestrogens and reduced risks of breast cancer, prostate cancer, and cardiovascular diseases. Other phytoestrogen health benefits are reduced osteoporosis (bone loss) and menopausal symptoms. Both flavonoid and lignan phytoestrogens also have antioxidant activity.
The low incidence of the above mentioned diseases in Asian populations is partly believed to be associated with their traditionally soy based diet, which is high in phytoestrogens. On average, Asians consume 50mg of isoflavones (a type of phytoestrogens) per kg body weight per day, while Americans on Western-diet consume 1 - 3 mg of isoflavones per kg body weight per day.
Medical phytoestrogen formulations are used by women in menopause as alternatives or complementary options to hormonal replacement therapy (HRT) because of concerns of side-effects or other considerations. Some studies also report potential benefits of phytoestrogens in lowering serum cholesterol levels.
What Foods are High in Phytoestrogens?
Estrogen is available in medically formulated pills. However, dietary estrogen (phytoestrogen) can also be found naturally in wide variety of plant-based foods, with the amount varying depending on the plant type. The main food sources of phytoestrogen are soybean and flaxseed, and their derivatives. Other food types such as nuts, oil seeds and herbs are also good sources phytoestrogens, eventhough in relatively low concentrations.
The type of phytoestrogens and their relative concentration varies from plant to plant. For example, isoflavone phytoestrogens are found in high concentration in soybean and soybean food products (eg. tofu) whereas lignan phytoetrogens are found mainly in flax seed.
Canadian researchers analyzed 121 food types including fruits, vegetables, herbs, grains, nuts and oils for their phytoestrogen content. The food types, as reported in the study, with the highest total phytoestrogen content are listed in the two tables below.
The phytoestrogen contents are averages based on analyses of multiple samples.
Table 1. Foods high in phytoestrogens content. The total phytoestrogens content is the sum of isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol), and coumestan (coumestrol). (1 µg = 0.000001 g)
| Phytoestrogens food sources | Phytoestrogens content (µg/100g) |
|---|---|
| Flax seed |
379,380
|
| Soy beans |
103,920
|
| Soy nuts |
68,730.8
|
| Tofu |
27,150.1
|
| Tempeh |
18,307.9
|
| Miso paste |
11,197.3
|
| Soy yogurt |
10,275
|
| Soy protein powder |
8,840.7
|
| Sesame seed |
8,008.1
|
| Flax bread |
7,540
|
| Multigrain bread |
4,798.7
|
| Soy milk |
2,957.2
|
| Hummus |
993
|
| Garlic |
603.6
|
| Mung bean sprouts |
495.1
|
| Dried apricots |
444.5
|
| Alfalfa sprouts |
441.4
|
| Pistachios |
382.5
|
| Dried dates |
329.5
|
| Sunflower seed |
216
|
| Chestnuts |
210.2
|
| Olive oil |
180.7
|
| Almonds |
131.1
|
| Cashews |
121.9
|
| Green bean |
105.8
|
| Peanuts |
34.5
|
| Onion |
32
|
| Blueberry |
17.5
|
| Corn |
9
|
| Coffee, regular |
6.3
|
| Watermelon |
2.9
|
| Milk, cow |
1.2
|
Lignans are one of the phytoestrogens. In table 2 are foods measured for their total phytoestrogen content and the lignan fraction.
Table 2. Total phytoestrogens and lignan content in vegetables, fruits, nuts and drinks.
| Food items | Lignan content (µg/100g) | Total phytoestrogens (µg/100g) |
|---|---|---|
| Vegetables | ||
| Soy bean sprouts | 2.2 | 789.6 |
| Garlic | 583.2 | 603.6 |
| Winter squash | 113.3 | 113.7 |
| Green beans | 66.8 | 105.8 |
| Collards | 97.8 | 101.3 |
| Broccoli | 93.9 | 94.1 |
| Cabbage | 79.1 | 80 |
| Fruits | ||
| Dried prunes | 177.5 | 183.5 |
| Peaches | 61.8 | 64.5 |
| Strawberry | 48.9 | 51.6 |
| Raspberry | 37.7 | 47.6 |
| Watermelon | 2.9 | 2.9 |
| Nuts and other legume seeds | ||
| Pistachios | 198.9 | 382.5 |
| Chestnuts | 186.6 | 210.2 |
| Walnuts | 85.7 | 139.5 |
| Cashews | 99.4 | 121.9 |
| Hazel nuts | 77.1 | 107.5 |
| Lentils | 26.6 | 36.5 |
| Beverages | ||
| Wine, red | 37.3 | 53.9 |
| Tea, green | 12 | 13 |
| Wine, white | 8 | 12.7 |
| Tea, black | 8.1 | 8.9 |
| Coffee, decaf | 4.8 | 5.5 |
| Beer | 1.1 | 2.7 |
| Other | ||
| Black bean souce | 10.5 | 5330.3 |
| Black licorice | 415.1 | 862.7 |
| Bread, rye | 142.9 | 146.3 |
Isoflavones are one of phytoestrogens. Here is a list of foods measured for isoflavones only.
Table 3. Isoflavones content in select foods.
| Food list | Total isoflavones content (mg/100 g) |
|---|---|
| Textured soy flour | 172.6 |
| Soy-based bacon bits | 118.5 |
| KASHI Go Lean cereal | 17.4 |
| Soy protein isolate | 91 |
| Edamame (raw green soybeans) | 48.9 |
| Miso | 41.5 |
| Soy Infant Formula (powder) | 26.3 |
| Raw tofu, regular | 23 |
| Red clover | 21 |
| Silken tofu | 18.0 |
| Soy-based sliced cheese | 14.5 |
| Soy-based burgers | 6.4 |
| Multigrain bread | 0.4 |
| Raw broccoli | 0.25 |
| Flaxseeds | 0.07 |
| Green tea, Japanese | 0.02 |
Phytoestrogen related articles:
Food sources of lignan phytoestrogens
Dietary Intake of Phytoestrogens Cuts the Risk of Colorectal Cancer
Description and the effect of phytoestrogens in the body?
Estrogens: What they are, functions, and synthesis
Phytoestrogens, osteoporosis and menopausal women
Tofu: phytoestrogen and health benefits
Phytoestrogen data source:
Thompson, L. U., Boucher, B. A., Lui, Z., Cotterchio, M., and Kreiger, N. 2006. Phytoestrogen content of foods consumed in Canada, including isoflavones, lignans and coumestan. Nutrition and Cancer, 54(2), 184-201.
Additional references:
Cassidy A. Potential risks and benefits of phytoestrogen-rich diets. Int J Vitam Nutr Res. 2003 Mar;73(2):120-6.
Ganry O. Phytoestrogens and prostate cancer risk. Prev Med. 2005 Jul;41(1):1-6.
Heather B. Patisaul and Wendy Jefferson. The pros and cons of phytoestrogens. Front Neuroendocrinol. 2010 Oct; 31(4): 400–419.
Tham DT, Gardner CD, Haskell WL. Potential health benefits of dietary phytoestrogens: a review of the clinical, epidemiological, and mechanistic evidence. J Clin Endocrinol Metab. 1998; 83(7):2223-2235.