Soya

Soya foods are a great fit with healthy eating guidelines as they are low in saturated fats and a source of high quality plant protein, fibre, micronutrients and isoflavones.

Soya is an excellent source of high quality protein.  Soya drinks typically provide 6 to 7 g of protein per 200 ml serving. The new high protein soya alternatives to strained yogurt provide 5 to 7.8g protein, whilst soya mince provides approx. 15g per 100g. 

Great for health

  • In the main, soya foods are low in saturated fat and can play an important role in cardiovascular health by displacing animal based foods high in saturated fat.
  • Naturally lactose-free and dairy-free, soya foods are ideal for people with lactose-intolerance and / or cow milk protein allergy.
  • Soya isoflavones are natural plant compounds belonging to the class of the polyphenols. These can have specific beneficial effects on health.

The soya bean is not only high in protein (approx. 38%) but it is one of the few plant foods to provide high quality protein similar to animal sources.  Additionally, soya has an exceptional fat profile being low in saturated fats whilst rich in polyunsaturated fats including omega-3 fatty acids.
Other nutrients:
  • A great source of fibre and oligosaccharides.
  • Source of vitamins B, E and K.
  • Source of calcium and potassium.
Soya foods
There are many soya foods on the market currently providing a range of nutritional benefits - many are low in saturated fat and provide high quality plant proteins, fibre and micronutrients as well as being a unique source of isoflavones.
  • Soya alternatives to dairy - low in saturated fats, a source of plant proteins and most are now fortified with vitamins B and D as well as calcium.
    • Soya drinks
    • Soya alternative to yogurts
    • Soya alterntaives to strained yogurts - high protein and fibre
    • Soya alternatives to desserts
  • Other soya foods:
    • Soya mince
    • Young edamame beans
    • Soya nuts (roasted edamame beans)
    • Tofu
Product Production process Use
Soya drinks Heated water extract of soya beans which have been ground and filtred. Soya drinks can be used on their own as a refreshing drink, to make coffees and milk based drinks, poured over cereals and used in various recipes.
Plant-based alternatives to yoghurt Fermented soya drink with yogurt cultures The soya-based alternative to yoghurt is ideal as a snack or dessert, used with cereal or to make fruit smoothies.  Come in a variety of flavours: plain, plain with grains or nuts, vanilla and fruit.
Soya dessert Made from soya drink. A delicious, indulgent treat in the afternoon or evening. Comes in vanilla, chocolate, dark chocolate and caramel.
Soya ice creams Made from soya drink. A great refreshing range of ice creams available in vanilla, coconut and hazelnut / chocolate.
Plant-based alternative to cream Made from soya drink Plant-based cream alternatives are an ideal replacement for the real thing! Perfect for sauces, pasta dishes and lots more!
Plant-based alternative to meat Tofu, also known as soya bean curd, is produced from curdling soya drink with a coagulant

Soya mince, made from ground soya beans and water.
A wide range of plant-based alternative to meat products ensures there is something for every meat lover!
Soya protein is one of the few commonly consumed plant proteins that is nutritionally complete, providing all the essential amino acids, in sufficient quantities, to meet the body's requirements.

Amino acids (AA)
Proteins are made up of amino acids A typical protein may contain 300 or more amino acids with each protein having its own specific number and sequence of amino acids.
There are twenty different amino acids commonly found in plants and animals. These can be classified as either essential amino acids (cannot be produced by the body during metabolism and so must be provided in the diet) or non-essential ( can be produced endogenously in the body from other proteins).

Eight amino acids are considered essential for adults:
  • Leucine
  • Isoleucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
Nine amino acids are considered essential for children:
  • The eight mentioned above
  • Histidine
Two semi-essential amino acids, as they can be metabolized in the body from essential amino acids:
  • Cysteine - made from methionine (sulphur containing)
  • Tyrosine - made from phenylalanine (aromatic)
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
Essential amino acid requirements for human growth and health have been determined by the FAO/WHO. When a protein meets the essential amino acid requirements it is classed as having a high biological value. Whereas if one or more essential amino acids are present in insufficient amounts, the protein is said to have a low biological value. The amino acid that is in shortest supply in relation to human needs is termed as the limiting amino acid.

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method used to measure protein quality, taking into account both the amino acid composition and digestibility. This method shows that among legumes, soya beans have some exceptional nutritional advantages. For example, out of all the plant proteins, soya protein has the highest biological value - comparable in quality to milk protein.
 


The amino acid composition in soya protein is excellent providing all the essential amino acids needed in a healthy diet.  The graph below illustrates essential amino acid requirements (as defined by the FAO) compared to the amino acid composition of soya protein.
 


As well as being a high quality protein, soya beans typically contain more protein than other legumes when expressed on a caloric basis. Approximately 35% - 38% of calories come from protein in soya beans, whereas other legumes provide around 20% - 30%.


Digestible Indispensable Amino Acids Score (DIAAS)
The FAO recently proposed a new method to more accurately determine the quality of dietary protein - the DIAAS (Digestible Indispensable Amino Acids Score). This method measures the digestibility of individual amino acids in the small intestine, thereby taking into account the bioavailability of the amino acids.

Figures derived DIASS are usually lower than PDCAAS.
The fat content of soya beans is approximately 20%. This is predominantly made up of polyunsaturated fats (PUFAs) with little saturated fat.

The major fatty acid of soya oil, is the essential omega-6 fatty acid, linoleic acid (LA, 18:2n-6), which accounts for approximately 55% of the total fat content.  However, unlike most other vegetable oils (the main exceptions being flax, walnut, and canola oils), soya beans also contain significant amounts (7-8%) of the essential omega-3 fatty acid, a-linolenic acid (ALA, 18:3n-3).

Not only do soya beans provide both essential fatty acids, they also provide an excellent balance of these fatty acids, which together have cardiovascular health benefits. ALA is thought to have a role in reducing the risk of coronary heart disease. In addition, omega-6-polyunsaturated fatty acids exert a cholesterol-lowering effect, mainly on LDL-cholesterol. Whereas omega-3-fatty acids decrease total triglyceride levels. 

Soya isoflavones belong to a group of plant compounds called phytoestrogens, also known as 'plant oestrogens'.  Phytoestrogens have a chemical structure similar to the endogenous oestrogen - oestradiol (see figure).  However, while the chemical structure of isoflavones are similar to oestrogen, the two function very differently in the body.  Phytoestrogens are present in a large number of plants and vegetables (cereals, celery, asparagus, broccoli, Brussel sprouts, lentils, legumes, etc.).

Three groups of phytoestrogens receive particular attention in food studies: isoflavones, coumestans and lignans.


Lignans occur mainly in whole-grain cereals, flaxseed, rye, legumes and berries. These are metabolised by the gut flora to enterolactone and enterodiol.

Coumestans are found mostly in alfalfa, clover and mungbean sprouts.
 
Soya isoflavones

The soya bean is unique as it’s the richest dietary source of isoflavones. Soya contains three types of isoflavones - genistein, daidzein and glycitein which account for approximately 50, 40 and 10% respectively of the total soya bean isoflavone content.
 
The three isoflavones in soya are genisteindaidzein and glycitein and their respective glycosides, represent approximately 50%, 40% and 10% of total isoflavone content respectively.

Figure :  Chemical structures of estrogen and the isoflavone genistein


 
Isoflavones are structurally similar to the hormone oestrogen (17 β-oestradiol). Although typically classified as phytoestrogens, they behave differently than oestrogen in the body. This is not surprising as small differences in chemical structure can lead to very different physiological effects. For example, cholesterol and phytosterols have almost identical chemical structures, but the former modestly raises blood cholesterol whereas the latter markedly lowers it. 

In addition to being phytoestrogens, isoflavones are classified as natural selective oestrogen receptor modulators (SERMs). 
  • SERMs exert oestrogenic effects in some tissues, anti-estrogenic effects in others, while they may have no effect at all in tissues affected by oestrogen.
  • SERMs developed by the pharmaceutical industry, such as tamoxifen and raloxifene, are designed to have some of the benefits of oestrogen without the adverse side effects.
At the molecular level, isoflavones differ from oestrogen because of the two known oestrogen receptors (ER): alpha (ERα) and beta (ERβ).

Isoflavones preferentially bind to and activate ERβ in comparison with ERα. In contrast, the hormone oestrogen has equal affinity for both receptors.

This difference is important because when activated these two receptors can have different and sometimes opposite physiological effects. In general, activation of ERα has a proliferative effect in tissues whereas activation of ERβ is anti-proliferative.

Isoflavones may exert effects unrelated to their interaction with ERs such as inhibiting the activity of enzymes over expressed in cancer cells.

Much of the confusion around isoflavones can be attributed to the results of rodent studies. Rodent studies are of questionable utility for providing insight into human nutrition due to the significant physiological differences between the two species. This is especially true in the case of isoflavones because of the differences in metabolism of these soya bean constituents between rodents and humans.


Asian and Western Soya and Isoflavone Intakes

Not surprisingly, because soya foods are not a traditional part of Western diets, isoflavone intake in the United States and Europe is typically less than 3 mg/d. In contrast, daily soya protein and isoflavone intakes of older Japanese adults ranges from 7 to 11 g and 25 to 50 mg, respectively.  These amounts translate to approximately one to two servings of soya foods a day. 


One serving of a traditional soya food, such as 250 ml soya drink (made from the whole soya bean) or 100 g tofu contains about 25 mg isoflavones.  Soya foods made from the whole soya bean contain approximately 3 mg of isoflavones per gram of protein. The amount may vary slightly due to growing conditions of the plant and due to climate variability.

Codex Alimentarius Commission. Document Alinorm 89/30. Report of the working group on protein quality measurement. FAO/WHO, Rome, 1989.

FAO/WHO/UNU. Protein quality evaluation. Report of a joint FAO/WHO/UNU Expert consultation. Rome: FAO food and nutrition paper Nr. 51, 1991 and Joint FAO/WHO/UNU Expert consultation. Energy and protein requirements. Technical Report Series, Nr. 724, WHO, Geneva, 1985

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Setchell KD, Cassidy A. Dietary isoflavones: biological effects and relevance to human health. J Nutr 1999;129:758S-67S.

Reiter E, Beck V, Medjakovic S, Jungbauer A. Isoflavones are safe compounds for therapeutical applications - evaluation of in vitro data. Gynecol. Endocrinol. 2009; 25: 554-80.

Oseni T, Patel R, Pyle J, Jordan VC. Selective estrogen receptor modulators and phytoestrogens. Planta Med. 2008; 74: 1656-65.

Murphy PA, Barua K, Hauck CC. Solvent extraction selection in the determination of isoflavones in soy foods. J Chromatogr B Analyt Technol Biomed Life Sci. 2002; 777: 129-38.