Phytoestrogens food sources

Withdrawal from anaboHc steroid treatment is not required before slaughter because residue levels in edible tissues are negligible, and are significantly lower than other sources of estradiol such as the normal endogenous production in humans and the phytoestrogens consumed in plant food sources (1). 

The three main classes of phytoestrogens (and common food sources) are isoflavones (soybeans), lignans (cereals and oilseeds such as flaxseed), and coumestans (alfalfa sprouts). The biologic potency of phytoestrogens varies and is less than that of synthetic estrogen. 

RJ Fletcher. Food sources of phytoestrogens and their precursors in Europe. Br J Nutr 89 Supple 1, S39-S43, 2003. 

Soybeans (Glycine max) are protein-rich legumes widely grown around the world as a food crop. They are the major dietary source of isoflavones, which are broken down in the intestine into the phytoestrogens genis-... 

Kuhnle, G.G.C. et al.. Variability of phytoestrogen content in foods from different sources. Food Chem., 113, 1184, 2009. 

In ovariectomized sheep, feeding with 3.5 kg daily of red clover silage for 14 days as the sole source of food (81-95 mg/ kg daily total phytoestrogens) resulted in increased plasma concentrations of T3 and T4 and increased thyroid follicle size as compared to sheep fed hay (Made] et al. 2002). 

Flax seed has a warm, earthy and subtly nutty, butter flavour. The seed can be eaten entirely, and has traditionally been used as an add-on to cereal or bread. Today flaxseed is experiencing a renaissance among nutritionists, the health conscious public, food and feed processors (see Chapter 6) and chefs alike. It is one of the richest sources of lignan and a-linolenic acid (> 50%), one type of fatty acid in the polyunsaturated co-3 fatty acid (PUFA) family, considered essential fatty acids. Lignans, like isoflavones, are one of the major classes of phytoestrogens, which are estrogen-like chemicals and act as antioxidants. 

Cereal foods are important components of the daily diet, providing carbohydrates, proteins, dietary fibre and vitamins. Cereals are also sources of many phytochemicals, including phytoestrogens, phenolic compounds, saponins, phytic acid and sterols. 

Clarke, D.B., Barnes, K.A. and Lloyd, A.S. (2004) Determination of unusual soya and non-soya phytoestrogen sources in beer, fish products and other foods. FoodAddit. Contam., 21,949-962. 

Carbohydrate foods are a good source of phytoestrogens, which may protect against breast cancer. However, studies related to carbohydrate intake and breast cancer have been inconsistent and are insufficient to establish an association between carbohydrates and breast cancer risk. 

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