by Toby Donnelly

It has been suggested that soya foods may provide health benefits to those over 50 years old due to soya’s positive effects relating to conditions that are important at this stage of life. Toby Donnelly, Registered Dietitian investigates

Introduction

The value of increasing soya in western diets, in order to benefit health, has been much debated in recent years. However, its incorporation in the eatwell plate does a great deal to validate its status as an important component of a healthy, balanced diet. It is suggested that soya containing foods may particularly provide health benefits to those over 50 years old due to soya’s positive effects regarding heart health, the menopause, bone health and weight management.

This article explores the latest evidence outlining relevant recommendations that can be made for incorporating soya into the daily diet of the 50 plus.

Summary of the nutritional benefits of soya

• Soya is a good source of high quality protein and is as accessible to the body as milk and meat proteins.
• 40% of soya’s energy value comes from fat, which is higher than other legumes. However, the key beneficial factor is the fat composition as soya is 80% poly-unsaturated fat of which around 55% is linoleic acid, and approximately 8% alpha-linoleic acid.
• Unlike other beans, soya contains very little carbohydrate. Only about 10% of which is largely sucrose.
• More akin with other pulses, soya is roughly 18% fibre and this is mainly soluble. However, it has a higher oligosaccharide content than most beans and so may also possess beneficial prebiotic properties.
• In terms of micronutrients, soya is again similar to other legumes and so is high in folate and other B vitamins. Soya also contains some iron; zinc and calcium which is important as soya containing foods often replace animal foods in the western diet. Recent findings highlight that the bioavailability of these is good.

What are the health benefits?

Many avenues of research relating to soya and the implications for health are being pursued. However, the most significant findings with the potential for practical application are as follows:

Heart disease

The cholesterol lowering effects of soya are well documented. It has been demonstrated that consumption of 25g soya protein daily has significant hypocholesterolaemic effects by reducing LDL cholesterol levels and serum triglycerides whilst increasing HDL cholesterol levels. This results in a significant reduction in overall risk of coronary heart disease. It is important that the soya protein dose is consumed in its natural form ie as soya milk, drinks or yoghurts, as it is thought that it is the soya peptides, either on their own or associated with the isoflavones rather than the isoflavones on their own that are the active component. In addition, consumption of multiple servings per day in preference to one daily serving also enhances the cholesterol lowering effect. Consequently it would appear that individuals with hypercholesterolaemia illustrate the greatest benefits from increasing soya in their diets.

Bone health

Several studies have highlighted potential benefits of soya on bone health in menopausal women. In relation to bone health isoflavones appear to be the active ingredient. A meta-analysis of randomised control trials concluded that a soya isoflavone intake of 90mg/day increases spinal bone mineral density over a period of as little as 6 months. Beneficial effects also become more significant when more than 90mg/day is consumed.

Menopause

There is considerable evidence to support the idea that soya intake can significantly reduce symptoms in menopausal women, particularly hot flushes. It is suggested that consumption from as little as 30 to 100mg/day of soya isoflavones in women who experience at least 4 hot flashes per day can
provide some symptomatic relief. The isoflavones can be consumed in soya foods or as a supplement as multiple doses throughout the day. Overall research suggests that soya isoflavones can offer some women assistance in reducing hot flushes and appears to work best in those women who suffer from severe hot flushes. Furthermore blood cholesterol levels shoot up at this time in womens life where over 7 out of 10 women will have raised cholesterol levels at this time. Consuming soya at this time of life can at least help with achieving health cholesterol levels.

Weight management and satiety

It is well established that protein is much more effective in inducing satiety than carbohydrate or fat. Recent findings support the theory that soya protein consumption, too, can increase satiety. One study highlighted that the satiety effect of soya milk is comparable with that of skimmed cow’s milk whilst containing additional beneficial agents such as isoflavones, essential fatty acids and phospholipids. Therefore, consumption of soya protein, as part of a healthy balanced diet, may suppress food intake & increase satiety, and so lead to a reduction in body weight.

Recommendations

In summary, soya has been shown to have a beneficial therapeutic role to play in the diet of those who are 50 years or above and already have existing conditions such as hypercholesterolaemia, menopause and obesity.

Obviously this may represent a considerable number of individuals in the UK population. Additionally, these benefits may be more important for those with multiple health conditions or those who are at risk of developing multiple issues, for example those peri- or postmenopausal women who are also overweight and so are at high risk of osteoporosis or heart disease.

Encouraging the inclusion of soya in the diet of these individuals will offer proven health benefits when consumed in the appropriate quantity and at regular intervals through the day, as part of a healthy balanced diet.

Overall the optimum amount and type of dietary soya necessary, as suggested by the research, to achieve these health benefits is variable dependant on the health benefit sought (as shown by table 1).

How can these proposals be achieved in practice?

In the UK soya product sales are on the increase but, on average, dietary intake remains relatively low. Significant dietary change may be required in order for individuals to achieve the outlined benefits their health. However,

soya intakes can be increased gradually and a variety of sources can be encouraged. The following are some examples of possible ways for boosting individuals intake of soya protein and soya isoflavones:

References

The British Nutrition Foundation. (2002) Soya and Health: A briefing paper.

McCance & Widdowson’s, The Composition of Foods. (1993) 5th Edition. Royal Society of Chemistry and Ministry of Agriculture, Fisheries and Food.

Ma D-F, Qin, L-Q, Wang, P-Y, Katoh, R. (2007) Soy isoflavone intake increases bone mineral density in the spine of menopausal women: Meta-analysis of randomised controlled trials.
Clin Nutr, doi:10.1016/j.clnu.2007.10.012.

Nahas EAP, et al. (2007) Efficacy and safety of a soy isoflavone extract in postmenopausal women: A randomised, double, and placebo-controlled study. Maturatis, doi:10:1016/j.maturitas.2007.08.012

The following references are from: ‘Discover the World of Soy: Impact on Health’ (2008) Alpro Soya, Science and Nutrition Dept:

USDA National Nutrient Database for Standard Reference, Release 20. (2007) Nutrient Data Laboratory. (Accessed Oct, 2007 www.ars.asda.gov/ba/bhnrc/ndl)

Young VR. (1991) Soy protein in relation to human protein and amino acid nutrition. J Am Diet Assoc 91:828-35

Gilani GS, Sepehr E. (2003) Protein digestibility and quality in products containing antinutritional factors are adversely affected by old age in rats. J Nutr 133:220-5

Sanwar G. (1997) The protein digestibility-corrected amino acid score method overestimates quality of proteins containing antinutritional factors and of poorly digestible proteins supplemented with limiting amino acids in rats. J Nutr 127:758-64

Karr-Lillienthal LK et al. (2005) Amino acid, carbohydrate and fat composition of soybean meals prepared at 55 commercial U.S. soybean processing plants. J Agric Food Chem 53:2146-50

Wu Z et al. (2004) Characterisation of vegetable oils: detailed compositional fingerprints derived from electrospray ionization fourier transform ion cyclotron resonance mass spectrometry. J Agric Food Chem 52:5322-8

Slavin J. (1991) Nutritional benefits of soy protein and soy fiber. J Am Diet Assoc 91:816-9

Carlsson N-G et al. (1992) Determination of oligosaccharides in foods, diets and intestinal content by high-temperature gas chromatography and gas chromatography/mass spectrometry. J Agric Food Chem 40:2404-12

Gibson GR, Roberfroid MB. (1995) Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. J Nutr 125:1401-12

Weaver CM et al. (2002) Bioavailability of calcium from tofu vs milk in premenopausal women. J Food Sci 68:3144-7

Zhao Y et al. (2005) Calcium Bioavailability of Calcium Carbonate Fortified Soymilk is equivalent to Cows Milk in Young Women. J Nutr 135:2379-82

Young VR, Janghorbani M. (1981) Soy protein in human diets in relation to bioavailability of iron and zinc. Cereal Chem 58:12-17

Lonnerdal B et al. (2006) Iron absorption from soybean ferritin in nonanaemic women. Am J Clin Nutr 83:103-7

Clair RS, Anthony M. (2005) Soy, isoflavones and atherosclerosis. Handb Exp Pharmcol 301-23

Anderson JW, Johnstone BM, Cook-Newell ME. (1995) Meta-analysis of effects of soy protein intake on serum lipids in humans. New Eng J Med 333:276-82

Sirtori CR, Eberini I, Arnoldi A. (2007) Hypocholesterolaemia effects of soy proteins: results of recent studies are predictable from the Anderson meta-analysis data. Br J Nutr 97:816-22

Katan MB, Grundy SM, Jones P, Law M, Miettinen T, Paoletti R. (2003) Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clin Proc 78:965-78

Anderson JW, Konz EC. (2001) Obesity and disease mangement: Effects of weight loss on co-morbid conditions. Obes Res 9:326S-62S

Nestel PJ, Yamashita T, Sasahara T et al. (1997) Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women. Anteriosci Throm Vas 17:3392-8

Wang W, de Mejia EG. (2005) A new frontier in soy bioactive peptides that may prevent age-related chronic diseases. Comprehensive Reviews in Food Science and Safety 4:63-78

Wang M-F, Yamamoto S, Chung H-M et al. (1995) Antihypocholesterolaemic effect of undigested fraction of soybean protein in young female volunteers. J Nutr Sci Vitaminol 41:187-95

Hori G, Wang M-F, Chan Y-C et al. (2001) Soy protein hydrolyzate with bound phospholipids reduces serum cholesterol levels in hypercholesterolaemic adult male volunteers. Biosci Boitechnol Biochem 65:72-8

Gianazza E, Eberini I, Arnoldi A, Wait R, Sirtoni CR. (2003) A proteomic investigation of isolated soy proteins with variable effects in experimental and clinical studies. J Nutr 133:9-14

Sketchell KD, Lydeking-Olsen E. (2003) Dietary phytoestrogens and their effect on bone: evidence from in vitro and in vivo, human observations and dietary intervention studies. Am J Clin Nutr 78:593S-609S

Williamson-Hughes PS, Flickinger BD, Messina MJ, Empie MW. (2006) Isoflavones supplements containing predominately genistein reduce hot flash symptoms: a critical review of published studies. Menopause. Sept – Oct 2006; 13(5):831-839

Nelson HD, Vesco KK, Haney E et al. (2006) Nonhormonal therapies for menopausal hot flashes: systematic review and and meta-analysis. Jama May 3 2006:295(17):2057-2071

Cheng G, Wilczek B, Warner M, Gustafsson JA, Landgren BM. (2007) Isoflavone treatment for acute menopausal symptoms. Menopause. May-Jun 2007;14(3 Pt 1):468-473

Welty FK, Lee KS, Lew NS, Nasca M, Zhou JR. (2007) The association between soynut consumption and decresed menopausal symptoms. J Womens Health (Larchmt). Apr 2007;16(3):361-369

Baba NH, Sanwaya S, Torbay N, Habbal Z, Azar S, Hashim SA. (1999) Higfh protein vs high carbohydrate hypoenergetic diet for the treatment of obese hyperinsulinaemic subjects. Int J Obes Relat Metab Disord 23 :1202-1206

Weigle DS, Breen PA, Matthys CC, Callahan HS, Meeuws KE, Burden VR, Purnell JQ. (2005) A high-protein diet induces sustained reductions in appetitie, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr 82:41-48

Anderson JW, Fuller J, Patterson K, Blair R, Tabor A. (2007) Soy compared to casein meal replacement shakes with energy-restricted diets for obese women: randomized control trial. Metabolism 56:280-8

Allison DB, Gadbury G, Schwartz LG, Murugeasn R, Kraker JL, Heshka S, Fontaine KR, Helmsfield SB. (2003) A novel soy-based meal replacement formula for weight loss among obese individuals: a randomised controlled clinical trial. Eur J Clin Nutr 57:514-522

Deibert P, Konig D, Schmidt-Trucksaess A, Zaenker KS, Frey I, Landmann U, Berg A. (2004) Weight loss without losing muscle mass in pre-obese and obese subjects induced by high soy protein diet. Int J Obes Relat Disord 28: 1349 –1352

Lukaszuk JM, Luebbers P, Gordon BA. (2007) Preliminary study: soymilk as effective as skim milk in promoting weight loss. J Am Diet Assoc 107:1811-4

Fang N, Yu S, Badger TM. (2004) Comprehensive phytochemical profile of soy protein isolate. J Agric Food Chem 52:4012-4020

Anderson GH, Moore SE. (2004) Dietary proteins in the regulation of food intake and body weight in humans. J Nutr 134:974S-979S

Velasquez MT, Bhathena SJ. (2007) Role of dietary soy protein in obesity. Int J Med Sci 4(2):72-82

Cope MB, Erdman Jr JW, Allison DB. (2007) The potential role of soyfoods in weight and adiposity reduction: an evidence-based review. Obes Rev (OnlineEarly Articles) doi:10.1111/j.1467-789X.2007.00390.x