Soya Nutrition, Health, and Sustainability
Soya is different to other beans and pulses. Compared to most other beans and pulses, soya beans have a much lower carbohydrate content, are higher in protein quality and content and are significantly higher in total fat –mainly polyunsaturated fat, including both essential fatty acids, linoleic acid, and alpha-linolenic acid.
Soya consumption is on the rise in the UK. Soya foods and drinks have now become mainstream in the UK and are a regular feature seen on supermarket shelves.
National dietary recommendations and soya. In the UK, fortified soya drinks are incorporated within the ‘Dairy and alternatives’ food group and soya proteins such as tofu and soya mince, within the ‘Beans, pulses, fish, eggs, meat and other proteins’ group of the Eatwell guide for over 5’s and adults.
The Eatwell guide introduced in 2016, incorporated environmentally sustainable factors within its recommendations and therefore prioritised plant food sources of protein over animal sources and reduced the recommended contribution from dairy foods and drinks.
The UK Government, Caroline Walker Trust and First Steps Nutrition Trust recommendations for children aged 1 to 5 years, include soya drinks and alternatives to yogurt and soya protein foods such as tofu and soya mince. Additionally, calcium fortified unsweetened soya drinks can be introduced from the age of 1 year as a main drink.
Soya is far better for the environment than meat and dairy. Compared to animal proteins, soya production for human consumption, produces significantly lower greenhouse gas (GHG emissions); uses significantly less land and fertilisers; requires less water; has a lower impact on biodiversity loss and causes lower damage to our seas and oceans.
The majority of soya grown on deforested land, including the Amazon,is used for animal feed and not for human consumption.
The EAT Lancet diet makes specific recommendations for soya foods within the protein food group. whilst UK dietary recommendations highlight soya foods and fortified drinks within the protein and dairy and alternatives food groups.
Soya consumption need not be exclusive. When providing direct consumer advice –we need to help consumers by keeping the message simple, positive and ensure it does not deviate too far from people’s current day-to-day habits.
Breakfast is a great easy win to drive more plant foods and reduce consumption of one of the main GHG gas contributors –simply switching from cow’s milk to fortified soya drink or a soya alternative to yogurt can significantly reduce our footprint without nutritional compromise.
Consumers and patients should be encouraged to eat more or switch to plant foods rather than emphasising reducing or cutting out meat/dairy altogether.
1-2 servings of soya foods and/or drinks daily. Based on the evidence, the favourable nutrition profile, and their environmental credentials 1-2 servings of soya foods or drinks as part of a balanced diet could provide benefits for both human health and planet health. Two servings daily would equateto100g soya mince OR half a block of tempeh OR 100g young green soya beans (edamame) OR a large (250ml) glass soya drink plus 200g serve of plain soya alternative to yogurt.
Dismissing the myths.The most comprehensive ever review of the scientific literature investigating the safety of soya and isoflavones was published online in Critical Reviews in Food Science and Nutrition on 28thMarch 2021. Ten global leading experts reviewed human data from over 400 publications and concluded that soya food and drinks consumed as part of a healthy balanced diet, is safeand has the potential to improve health outcomes.
The totality of the evidence indicates that neither soya nor soya isoflavones negatively impacted on women’s or men’s health. Outcomes assessed included breast cancer, hormone levels, children’s growth and development, men’s health including feminisation.Much of the concerns stemmed from animal studies, which are now well-established to be a poor representation of how isoflavones are absorbed and metabolised in humans.
Why isoflavones are not oestrogen
Soya foods and drinks contain naturally occurring plant components called isoflavones. Soya isoflavones’ chemical structure is similar to the human hormone oestrogen, it is not identical. Isoflavones are sometimes classified as a phytoestrogen or plant oestrogen.
The extensive research has demonstrated that isoflavones actdifferently to oestrogen in the human body –here comes the technical bit:
- Unlike human oestrogen which binds with equal affinity to the two oestrogen receptors (alpha and beta) found in the human body, isoflavones preferentially bind to oestrogen receptors beta rather than alpha. Because of this, they are now more correctly classified as Selective Oestrogen Receptor Modulators (SERMs).
- The two oestrogenreceptors (alpha and beta) have different tissue distributions and, when activated, can produce different effects in the body.
- Sometimes, isoflavones can produce a weak oestrogen-like effect in the body without increasing or altering human oestrogen levels. They do this by interacting directly with oestrogen receptors found on organs and tissues around the body. As isoflavones are different compounds to oestrogen, they do not affect oestrogen levels.
- Sometimes, they produce effects inthe body that are opposite to those of oestrogen.
- In many cases, they do not have any effect at all in tissues that are affected by human oestrogen.
- Isoflavones have been shown to possess other biological effects unrelated to oestrogen e.g., as antioxidants.
Men need not worry about the impact of soya on testosterone levels. A meta-analysis published this year that included 41 human studies and over 1,750 men showed no effect on testosterone or oestrogen levels.
Soya builds muscle as effectively as whey and other animal proteins.The latest evidence demonstrates that adequate protein intakes evenly consumed throughout the day alongside weight resistance exercise, is most critical for muscle building.
New research reports that over the long-term, there is no difference between consuming soya or animal proteins for building muscle size or strength amongst those performing weight resistance exercises. Thus, there is no need to consume more plant proteins than animal proteins to gain the same muscle effect. As long as one is consuming adequate energy and protein and the overall diet is balanced, there will be no difference in muscle gains for those wishing to follow a vegan, vegetarian or meat containing diet.
Soya can help with hot flushes in menopausal women and provide heart health benefits.The evidence indicates that consuming around 2 servings of soya foods and/or drinks as part of a balanced diet and lifestyle can be a positive for women during the menopause, especially with regard to hot flushes and cardiovascular health.
Hot flushes. Approximately50mgof isoflavones consumed daily(2 servings of soya foods and/or drinks) have been associated with reduced frequency and severity of hot flushes.The exact mechanism is not yet fully understood, but it is speculated, that isoflavones attach themselves to oestrogen receptors in the body and exert a weak oestrogen-like effect and as they are a different compound to oestrogen, they do not alter oestrogen levels in the body.
Heart health.The menopause increases cardiovascular risk and blood cholesterol levels. Soya foods and drinks low in saturated fat can help maintain normal blood cholesterol levels and soya isoflavones have been associated with improved function of cell lining of blood vessels.
Soya is safe for women at risk of developing or with breast cancer.Safety of soya with regard to women’s breast cancer risk, breast cancer sufferers and risk of recurrence is supported by the leading global cancer organisations: the American Institute of CancerResearch (AICR), American Cancer Society(ACS), the World Cancer Research Fund (WCRF) and WCRF continuous update programme and European Food Safety Authority.
Most population studies show that soya consumption certainly does not increase breast cancer risk with some studies indicating a modest (10-20%) reduction.
Additionally, there is some evidence to indicate that starting consumption during adolescence and maintaining intake during adulthood has a significantly more marked effect in reducing risk of breast cancer.
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