Parents may chose a soya formula for ethical or cultural reasons - or because their baby cannot be breast fed and cannot tolerate the standard cow?s milk formulae. But are they ?safe?? Following on from her investigations into hydrolysed and elemental cow?s milk formulae, Sarah Merson now checks out the soya versions.

A number of infant health issues, including lactose intolerance and milk allergy, have led parents seek out other feeding options, and where an infant has a medical reaction to other formulae, soya formulae are often offered on prescription.

In fact, as a result of unanswered health concerns, the Committee on Toxicity (CoT) now recommend to the Food Standards Agency that soya-based baby milks are only used when 'indicated clinically'. According to a report from the Scientific Advisory Committee on Nutrition (SACN), in 2003 however, there has been a steady decline in the total number of prescriptions issued for soya-based formulae since 1994.

So, does this mean that soya formulae is likely to become obsolete? We look at the background behind the health scares, and consider why soya formulae should be limited to clinical use only.

Phytoestrogens

Soya contains naturally occurring substances known as phytoestrogens, which have similar, though much weaker, properties to human oestrogen - the hormone involved in the development of female characteristics.

Due to their phytoestrogen content, soya-derived products have been under much scrutiny for the past 10 years. In the case of infants using soya-based formulae, alarm bells were raised over the possibility of hormonal imbalance in early life, which could permanently affect sexual development and fertility in later life. Questions have also arisen over whether phytoestrogen intake could interfere with thyroid function in babies.

It has been acknowledged that there is no evidence to suggest that people in countries such as Japan who routinely consume large quantities of soya have reduced fertility or altered sexual development, but...

Traditional v. modern

According to CoT, processing does affect the levels of phytoestrogens in soya. Traditional fermentation reduces the levels of isoflavones two to threefold but modern factory processes do not.

Moreover, modern American strains of soya (which are often contained in baby formulae as well as many other products) have significantly higher levels of isoflavones than Japanese or Chinese ones because they have been bred to be more resistant to pests. (One way to tackle pests is to stop them breeding by making them infertile. It turns out that unfermented soya did play one role in traditional Asian diets - it was eaten by monks to dampen down their libido!).

What is more, ‘Soya formula milk is a [recent] western invention. There is not the historical evidence to show it is safe’, says Professor Richard Sharpe, head of the Medical Research Council's Human Reproductive Sciences Unit at Edinburgh University.

Anyhow, according to Consultant toxicologist, Dr Mike Fitzpatrick who looked into the historic soya consumption in Japan and China (on which many studies are based), these populations did not actually eat that much soya and what they did eat tended to have been fermented for months. Babies who are using soya formulae, on the other hand, are consuming vast quantities.

A real risk?

On-going research still fails to give a definitive answer on whether the speculative health risks are truly valid. Adverse effects on the development of reproductive organs and fertility have been reported in animals after administration of large doses of phytoestrogens however, and although there is no evidence of similar effects in humans, the DoH's Committee on Toxicity (CoT) has concluded that there is evidence of potential risk and have recommended to the Food Standards Agency (FSA) that soya-based baby milks are only used when 'indicated clinically'.

Prescription only

In reality, this would mean a necessary change in the marketing of soya-based formulae so that they become a prescription-only item. This would prevent off-the-shelf purchases and parents using them without having discussed it first with a health professional.

Moreover, because so little is still known about the effect of soya on young infants, all infants using it should, ideally, be monitored. This would be much easier if the product was only obtained on prescription. The FSA are yet to take this action.

Shared allergenicity

A joint statement by the European Society for Allerology and Clinical Immunology (ESPACI) and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) recently highlighted another reason to reduce the use of soya formulae in the treatment or prevention of cow's milk allergy.

According to the ESPGHAN, prospective studies have shown that soya-based formulae are as allergenic as conventional cow's milk based formulae. They therefore suggest that they should not be recommended for the prevention of food allergy. Further studies however, are required.

The ESPGHAN committee concluded that:
• infants with cow's milk protein allergy who are not breast-fed should receive 'extensively' hydrolysed protein from cow’s milk or, in selected cases, a product based on an amino acid mixture.
• Bottle-fed infants with a documented hereditary risk of allergy should be exclusively fed a formula with a confirmed reduced allergenicity which may reduce the incidence of adverse reactions to food, especially cow's milk protein.
• Exclusive breastfeeding during the first 4-6 months might greatly reduce the incidence of allergy and is strongly recommended.

Reducing phytoestrogens

None of the soya available to the industry is naturally low in phytoestrogens and therefore the only option is to reduce the levels by processing. This is exactly what the government urged manufacturers to do in 1996.

The Food Commission, in their own 1998 investigation, found that companies had failed to respond to this demand and that they 'blocked direct enquiries'.

More recently however, suppliers of soya protein isolate, used in the manufacture of soya-based formulae, have been investigating means of reducing phytoestrogen levels. One major company is looking at the possibility of using a non-solvent extraction procedure although the work is still at an early stage. An infant formula manufacturer in the USA is also investigating the use of an ion-exchange method to reduce levels. The formula manufacturers have pointed out that it is important that any new process does not affect the nutritional quality of the final product as any significant change would require its re-assessment by relevant expert committees.

Soya formulae

Wysoy - SMA Nutrition
Dairy free, based on natural soya.

Farley’s Soya Formula - Heinz
Soya-based product, containing no animal products.

First published 2007

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