The power of peanuts

Jennette Higgs
Consultant nutritionist, American Peanut Council

New studies (1, 2) have shown that peanuts are in the same league as fruit when it comes to contributing to our diet and health status.

Taken together, these studies provide further evidence that eating peanuts daily can actually make you healthier.

Commenting on these results for the UK Jeya Henry, Professor of Human Nutrition at Oxford Brookes University explains "Peanuts are the ultimate functional food in a nutshell! Just a handful a day can give a good nutrient boost to the diet and far from causing weight gain, can help with dietary control as part of a healthy diet and lifestyle":

Professor Henry added, "Peanuts, with their low GI, may be a better option to satisfy appetite and reduce overeating!"

Recent studies at Oxford Brookes University indicate that peanuts have one of the lowest GIs of all nuts (3). At just 14, the GI of peanuts is similar to green vegetables, which may help to explain how this relatively energy dense food can aid effective weight loss.

Researchers from the Pennsylvania State University, USA have shown that it’s not the people eating peanuts who end up overweight or obese. Just one handful of peanuts or 2 tbsp (30g/1oz) peanut butter daily, positively improves overall diet quality without causing an increased body mass index (a measure of obesity).

A second study from the University of Florida has revealed that peanuts are as rich in a wide variety of helpful antioxidants as many kinds of fruits. Antioxidants include vitamins A, C & E and polyphenols, the group of chemicals found in plant-based foods that help protect against disease.

Although it is well known that peanuts are a good source of vitamin E, they had not been considered a rich source of antioxidants because there was a lack of data on their polyphenol content. The Florida team have shown that peanuts contain high concentrations of polyphenols – chiefly a compound called p-coumaric acid, which has been shown to block lipid peroxidation and reduce cholesterol levels. What’s more, roasting increases the level of p-coumaric acid in peanuts, boosting their overall antioxidant content by as much as 22 percent.

Stephen Talcott, Assistant Professor of Food Science and Nutrition and lead researcher confirms "roasted peanuts are about as rich in antioxidants as blackberries or strawberries and are far richer in the chemicals than fruits such as apples, carrots or beets".

The Penn State nutrition team, reporting in the Journal of the American College of Nutrition studied diet intake records from over 14,000 free-living American men, women and children as part of the US Department of Agriculture national survey. The results showed that the peanut consumers (some 24% of total sample) had a significantly higher healthy eating index than non-consumers, suggesting that eating peanuts as a regular part of the diet helps to improve its nutritional quality.

Regular peanut consumers had higher intakes of vitamin E and folate, magnesium, zinc, iron, heart-healthy monounsaturated fat and dietary fibre, and lower intakes of cholesterol. Reassuringly, peanut consumers had leaner bodies than non-consumers, as measured by body mass index (BMI), a measure of body weight, confirming yet again that this powerhouse of nutrition doesn’t cause weight gain when included within the diet.

Peanuts and weight management
Three independent research groups have reported in the literature that moderate fat diets including peanuts can help with weight loss (4-6). Studies (7) have shown that peanuts help to satisfy appetite when eaten as a snack and as such may help regularise eating patterns.

The Penn State team found that body mass index (BMI), a measure of body weight, was lower in peanut users compared to non-users, even though energy intakes were higher. Furthermore, BMI did not change with increasing peanut consumption, despite the fact that almost a third of the peanut consumers were eating more than two, or more than three handfuls of peanuts per day.

The authors suggest that this finding is either due to reduced calorie intake from other foods or to increased physical activity levels in peanut consumers. Nevertheless, the results confirm that, contrary to public opinion peanut consumption per se is not a cause of weight gain.

Peanuts and CHD
Consistent evidence from five major epidemiological studies shows that regularly consuming peanuts as part of a healthy diet can help reduce coronary heart disease (CHD) risk (8). Peanut consumers in the Penn. State study had significantly higher intakes of dietary fibre and vitamin E, both valuable nutrients that can help reduce risk of CHD and lower cholesterol levels. Antioxidants and polyphenols are chemicals that block the damaging effects of free radicals on cells.

Free radical damage is linked to heart disease, as well as stroke, certain cancers and macular degeneration of the eye. The significant polyphenol content of peanuts found in the Florida work may help to explain results from other studies that have suggested the cardio-protective effects of peanuts appear to be more than can be explained by their beneficial effects on blood fat levels alone.

Peanuts can contribute to improving the quality of the British diet
Recent findings from the National Diet and Nutrition Survey for British children 4-18yrs (9) suggest that significant proportions of young people have intakes of zinc and magnesium below the lower reference nutrient intake (LRNI)*. Folate also may be a cause for concern. Dietary intakes of magnesium are also below recommended levels in around a sixth of UK adults (10) and adequate folate intakes are especially important for women of child-bearing age. Adults and children in the Penn. State study who consumed peanuts had higher intakes of all these marginal nutrients than non-consumers.

Peanuts and salt
The Florida study suggests that roasted peanuts have higher levels of antioxidants than raw peanuts, however in the UK roasted peanuts are more commonly salted. The Government recommends overall reductions of salt intake to 6g/day. Individuals can choose which foods they eat that provide salt and which foods they eat less often. The research from Florida and Penn. State both highlight the significant nutrient boost that a daily handful of peanuts can offer. As well as increasing our intakes of fruit and vegetables, including roasted peanuts in place of highly processed foods, which tend to be high in salt, can help to improve diet quality.

Peanut consumption in the UK
Current consumption of peanuts in the UK is estimated to be less than 3g/person/day (11). For the UK, increasing intakes of nutrient dense peanuts to at least a daily handful (30g) would make a positive contribution to improving overall quality of the average diet, and provide a protective antioxidant boost, without fear of weight gain.

*Children under five years of age should not be given whole or chopped nuts due to the risk of choking. Anyone with a history of nut allergy should avoid peanuts and any foods containing peanuts. Published references cited in this release:
1. Griel AE, Eissenstat B, Juturu V, Hsieh G, Kris-Etherton PM (2004) Improved diet quality with peanut consumption. Journal of the American College of Nutrition. 23; 1
2. Talcott ST, Passeretti S, Duncan CE, Gorbet DW (2005) Polyphenolic content and sensory properties of normal and high oleic acid peanuts. Journal of Food Chemistry. 90; 379-388.
3. Personal communication
4. McManus K , Antinoro L, 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. 25; 5: 1503-1511
5. Sabate J (2003). Nut consumption and body weight. American Journal of Clinical Nutrition. 78(suppl): 647s-50s
6. Garcia-Lorda P, Megias Rangil I & Salas-Salvado J (2003). Nut consumption, body weight and insulin resistance. European Journal of Clinical Nutrition. 57( suppl1): S8-S11.
7. Alper, CM & Mattes, RD (2002). Effects of chronic peanut consumption on energy balance and hedonics. International Journal of Obesity. 26; 1129-1137
8. Alper, CM & Mattes, RD (2003). Peanut consumption improves indices of cardiovascular disease risk in healthy adults. Journal of the American College of Nutrition. 22; 2: 133-141.
9. Gregory JR, Lowe S, Bates CJ, Prentice A, Jackson LV, Smithers G, Wenlock R, Farron M. (2000) National Diet and Nutrition Survey: young people aged 4 to 18 years. Volume 1: Report of the diet and nutrition survey. The Stationary Office, London.
10. Henderson L, Irving K, Gregory JR, Bates CJ, Prentice A, Perks J, Swan G, Farron M (2003) National Diet and Nutrition Survey: Adults aged 19 to 64 years, Volume 3: Vitamin and mineral intakes and urinary analyte. The Stationary Office, London.
11. Higgs, J (2003). The beneficial role of peanuts in the diet- Part 2. Nutrition and Food Science Journal. 33; 2: 56-65.

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