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Copyright © 2004, Emerald Group Publishing Limited
Daily peanut and peanut butter consumption reduces risk of gallstones
New research has found that consuming peanuts or peanut butter more than five times a week is associated with a significantly reduced risk of gallbladder disease.
Reporting in the American Journal of Clinical Nutrition this month, researchers from the Harvard School of Public Health found that, compared with those who rarely ate peanuts or peanut butter, women consuming one serving of peanuts (28 g, 1 oz) almost daily had a significant, 20 per cent reduced risk of cholecystectomy (removal of a diseased gallbladder). Similarly, eating half a serving of peanut butter (about one good teaspoon) five or more days per week reduced the risk by 15 per cent.
Gallbladder disease is common in Western countries and is a major cause of abdominal ill health, due to the formation of gallstones in the gallbladder. A staggering 50,000 operations to remove the gallbladder are carried out each year in the UK. It effects mainly women, although it can occur in men. In Western countries, some 80 per cent of gallstones are cholesterol stones and their development is linked to high blood triglyceride levels and low levels of the protective HDL cholesterol. Peanuts are rich in the beneficial cholesterol-lowering fatty acids and animal studies have confirmed that unsaturated fats, such as those in peanuts may reduce the development of gallstones.
The Harvard study suggests a threshold effect, with protection against gallbladder disease occurring in those women who consumed peanuts or peanut butter as a regular, almost daily, part of their diet. This study adds to the growing list of research reports that highlight the significant protective effect of small daily servings of peanuts and peanut butter against coronary heart disease, type 2 diabetes, obesity, and now gallbladder disease.
Nuts have traditionally been seen as foods to avoid, due to their high fat content and the perception that this will cause weight gain. Several studies have now shown, however, that including peanuts and peanut butter in calorie-controlled diets can help reduce weight and keep it off long term.
These latest results support this since the women who consumed more nuts tended to weigh less.
The researchers suggest that the monounsaturated and polyunsaturated fats in nuts, peanuts and peanut butter may act as inhibitors to gallstone formation. In addition, their results show that even after controlling for the intake of specific fatty acids, the protective effect of nuts persists. This suggests that other nutrients in nuts may also be contributing to the reduction in risk for gallbladder disease. Peanuts are high in dietary fibre, one serving providing some 1.4 g (one-twelfth of the daily recommended level). It is well known that dietary fibre offers protection against cholesterol gallstone formation by removing some of the constituents of gallstones and by improving insulin sensitivity. Peanuts also contain many other bioactive compounds, such as phytosterols that may lower cholesterol levels by inhibiting its absorption. Nuts, peanuts and peanut butter are a good source of magnesium, which may play a role in improving insulin sensitivity and hence may reduce the development of gallstones.
This valuable piece of research, from the now famous Nurses Health Study, shows yet again that peanuts and peanut butter are beneficial foods to include in a healthy, balanced diet. Not only are they a tasty and nutritious snack, but it is reassuring to note their protective health benefits.
This research was supported by grants from the US National Institutes of Health.
The Nurses Health Study: established in 1976 by researchers at the prestigious Harvard School of Public Health, Boston, USA, the Nurses Health Study includes detailed medical and lifestyle information on 121,700 registered female nurses aged 30-55yrs, in the USA over nearly 30 years. Follow-up questionnaires are sent to all participants every two years to collect data on potential risk factors for diseases and identify newly diagnosed diseases, such as CHD and diabetes.
Food frequency questionnaires show how many women were eating nuts five or more times per week. Of the 83,000 female nurses who were followed for an average of 16 years in the Nurses Health Study, 749 women ate peanut butter almost daily compared to 82 for peanuts and 32 for other nuts.
One serving peanuts=1oz or 28.6 g. One serving peanut butter or 1 tablespoon.
Gallstones are the commonest cause for emergency hospital admission with abdominal pain in developed countries and account for an important proportion of healthcare expenditure. Around 5.5 million people have gallstones in the UK, and over 50,000 cholecystectomies are performed each year.
Laparoscopic cholecystectomy was introduced in 1987 and 80 per cent of cholecystectomies in the UK are now carried out using this technique, which reduces the risk associated with surgery in morbidly obese patients.
Published references cited in this release:
Chung-Jyi Tsai, Michael F. Leitzmann, Frank B. Hu, Walter C. Willett.
Giovannucci, E.L. (2004), “Frequent nut consumption and decreased risk of cholecystectomy in women”, American Journal of Clinical Nutrition, Vol. 80 No. 1, pp. 76-81.
Beckingham, I.J. (2001), “ABC of diseases of liver, pancreas, and biliary system: gallstone disease,” British Medical Journal, Vol. 13, January.
Kris-Etherton, P.M. (2001), “The effects of nuts on coronary heart disease risk”, Nutrition Reviews, Vol. 59 No. 4, pp. 103-11.
Hu, F.B., Manson, J.E. and Willett, W.C. (2001), “Types of dietary fat and risk of coronary heart disease: a critical review”, Journal of the American College of Nutrition, Vol. 20 No. 1, pp. 5-19.
McManus, K., Antinoro, L. and Sacks, F. (2001), “A randomised controlled trial of a moderate fat, low-energy diet with a low fat, low-energy diet for weight loss in overweight adults”, International Journal of Obesity, Vol. 7 No. 5, pp. 1503-11.
Jiang, R., Manson, J.E., Stampfer, M.J., Liu, S., Willett, W.C. and Hu, F.B. (2002), “A prospective study of nut consumption and risk of type II diabetes in women”, Journal of the American Medical Association, Vol. 288 No. 20, pp. 2554-60.
For further information on the nutritional benefits of peanuts and peanut butter, visit Web site: www.peanutsusa.org.uk/su4, or please contact: Jennette Higgs, Consultant Nutritionist/ Dietitian and Media Specialist for the American Peanut Council. E-mail: email@example.com; Tel: 01327 354632.