THE HEALTH BENEFITS OF REGULAR NUT CONSUMPTION
Article first published online: 28 FEB 2012
© 2012 The Author. Nutrition & Dietetics © 2012 Dietitians Association of Australia
Nutrition & Dietetics
Volume 69, Issue 1, pages 69–73, March 2012
How to Cite
(2012), THE HEALTH BENEFITS OF REGULAR NUT CONSUMPTION. Nutrition & Dietetics, 69: 69–73. doi: 10.1111/j.1747-0080.2012.01577.x
- Issue published online: 28 FEB 2012
- Article first published online: 28 FEB 2012
Continuing education and the APD program
This quiz is an ideal activity for APD members to include in your CPD log, where it relates to personal learning goals. Record the time taken, to the nearest hour, to complete the quiz and any associated research.
This quiz has been prepared by Lisa Yates, Adv APD and Liz Munn, APD, dietitians working for Nuts for Life—a health education initiative funded by the Australian Tree Nut Industry and with Australian Government matched funding for R&D activities through Horticulture Australia. Correspondence should be addressed to Lisa Yates, Program Manager, Nuts for Life at email@example.com
Nuts have been widely consumed in many different cultures since prehistoric times.1 Nuts are nutrient dense and help improve the quality of the diet.2 Nuts were included in the modelling for the recent Australian foundation and total diets3 which suggests that for foundation diets, between 2 and 14 serves of nuts a week is required, where a serve is 30 g and is dependent on age, gender, energy needs, and if pregnant or lactating. However, when building total diets from the foundation diet, a 30 g serve daily can be included at all energy levels modelled.3
Australians' diets contain far fewer nuts than 30 g each day. While the 1995 National Nutrition survey results are dated, they found adults aged 19 years and over ate an average of 5 g of nuts per day, and children even less.4 A comparison5 of the 1995 children's figures with the 2007 Australian National Children's Nutrition and Physical Activity Survey6 concluded that consumption of all nuts had further fallen.
This continuing education quiz provides dietitians with updated knowledge on the health benefits of regular nut consumption and references for further reading. It aims to assist dietitians to understand how nuts can contribute positively to the nutrient profile of diets, with particular emphasis on clarifying their role in dietary advice addressing lifestyle-related disease.
- 1Which of the following best reflects the findings of major observational studies on nut consumption and heart disease risk?
- a. Occasional nut consumption has no effect on heart disease risk.
- b. Regular consumption of nuts (about 30 g five times per week) can significantly reduce heart disease risk.
- c. The fat delivered by nuts increases heart disease risk, but only marginally.
- d. There is insufficient evidence that nuts can have any influence on cardiovascular disease.
- 2Which of the following best reflects the results of meta-analyses on nut consumption and blood lipids?
- a. Around 30 g of nuts a day can reduce total and LDL blood cholesterol and triglycerides by 5–10%.
- b. Around two handfuls (∼60–70 g) of nuts a day can reduce total and LDL blood cholesterol and triglycerides by 7 and 10% respectively.
- c. Only a handful of almonds or walnuts can significantly lower blood cholesterol.
- d. Nuts have no positive effects on blood cholesterol levels.
- 3Which of the following nutrients do nuts as a category contain?
- a. Monounsaturated and polyunsaturated fats, including the plant omega 3—alpha linolenic acid
- b. Antioxidant vitamin E
- c. Antioxidant minerals such as copper, manganese, selenium and zinc
- d. Fibre, plant sterols and the amino acid arginine
- e. Polyphenols such as resveratrol
- f. All of the above
- 4Which of the following statements least reflect the current literature on nut consumption and diabetes?
- a. A study of over 84 000 women found that regular nut consumption can significantly reduce the risk of developing type-2 diabetes.
- b. Studies have shown that including nuts in meals containing carbohydrate can reduce postprandial blood glucose levels.
- c. Studies have shown nuts consumption can improve insulin resistance.
- d. Nuts should not be consumed as part of the diet for diabetes.
- 5Which of the following statements about the role of nuts in weight management is correct?
- a. Studies show people who regularly eat a handful of nuts are more likely to have a lower body mass index (BMI).
- b. Nuts are high in fat which is readily absorbed and this explains why nuts are fattening.
- c. Eating nuts increases the appetite because they inhibit the satiety hormones in the gut.
- d. A recent study found that weight gain after 4 years was positively associated with nut consumption.
- 6Which of the following nut allergy statements is correct?
- a. Women should not eat nuts during pregnancy and lactation as it will increase the risk of nut allergy in their child.
- b. Someone with an allergy to a specific nut can eat all the other nuts.
- c. Roasting nuts increases the allergenic potential of all nut types.
- d. They are all incorrect.
Evidence from a number of observational studies7–11 has found that nut consumption may be protective against cardiovascular disease. In general, consuming 30 g of nuts at least five times a week appears to reduce the risk of developing heart disease by around 30–50% compared with those who eat nuts less than once a week or never eat nuts.7–11Table 1 summarises major studies that support this finding.
A meta analysis of 25 nut and cholesterol-lowering intervention trials found that around two handfuls of nuts (∼67 g) on average each day significantly reduced total and LDL cholesterol by 5 and 7%, respectively (P < 0.001), without affecting HDL levels and reduced triglycerides by 10% (P < 0.05).12 This is further supported by two other meta-analyses specifically on almonds13 and walnuts14 which also support eating at least a handful a day to significantly lower total and LDL cholesterol by around 5% (P= 0.05). Studies of almonds show evidence of a dose response across an intake range of 34–100 g/day, suggesting that a greater benefit may be obtained from a higher intake of nuts.15,16 Significant cholesterol lowering can also be achieved by a variety of nuts including hazelnuts, macadamias, pecans and pistachio.17–28 Preliminary research is also finding that nuts affect LDL particle size with a reduction in small LDL cholesterol.28,29
As a natural, whole food nuts are nutrient dense, containing a number of nutrients and phytochemicals which can maintain heart health through different mechanisms.30 It is a case of the sum being greater than the individual parts. Monounsaturated and polyunsaturated fats help regulate cholesterol production.31 Alpha linolenic acid may play a role in maintaining heart health.32 Vitamin E, copper, manganese, selenium and zinc are antioxidant vitamin and minerals30 while polyphenols such as resveratrol have antioxidant and anti-inflammatory functions.33 Dietary fibre and plant sterols help lower cholesterol re-absorption in the gut,34,35 and the amino acid arginine improves endothelial function.36 Together, these may reduce the risk of atherosclerosis and heart disease.30
Nut consumption has positive effects on postprandial blood glucose and insulin resistance.37 Studies have found that including nuts can reduce the rise in blood glucose levels following a meal containing carbohydrate.38–40 Nut consumption may also improve insulin resistance.41 A study of ∼84 000 women found that those who ate ∼30 g serve of nuts, five or more times per week, had a 27% lower risk of developing diabetes compared with those who never or rarely ate nuts.42
Observational evidence shows that those who eat a small serve of nuts (∼30 g) 2–5 times a week do not weigh more than people who consume nuts less than once a week or never eat nuts.7–10,43,44 There is a trend towards frequent nut consumers having a lower BMI than non-consumers and that eating nuts regularly may reduce the risk of weight gain and developing obesity.44Table 2 summarises major studies that support this finding. A recent study published in the New England Journal of Medicine found that weight gain after 4 years was negatively associated with nut consumption.45
While nuts are high in fat, nut consumers excrete more fat. As a whole food with fibre, the digestion and absorption of the energy in nuts appears incomplete. Up to 15% of the energy in nuts is not absorbed.46–49 The fat and energy content of nuts, analysed in the laboratory and labelled on packs, may not reflect true fat and energy absorption by the body. Nut consumption can reduce the appetite as the fat in nuts can increase satiety hormones such as cholecystokinin in the digestive system.46,47,50,51 It appears that the action of shelling nuts also reduces energy intake as study participants ate less nuts when they had to shell their own.52
According to the Australasian Society of Clinical Immunology and Allergy, there is no evidence to suggest that women should make any dietary restrictions during pregnancy and lactation to reduce the risk of their children developing food allergies.53 Due to the risk of cross contact between different nut varieties in food manufacturing plants, it is a good idea to recommend nut allergic patients to avoid all nuts unless they are able to source the non-allergic nuts direct from the grower or a company that only sells that one nut variety. Processing does not change the allergenic potential of every nut variety but may dampen it in some nuts such as hazelnuts and pistachios.54–57
|Study||Number of subjects (sex)||End points||Nut consumption frequency||Relative risk(a)||P for trend|
|Nurses Health8Study||86 016 (F)||Total CHD||Almost never||1.00|
|≥5 serves/week||0.65 (0.47–0.89)||0.0009|
|Fatal CHD||Almost never||1.00|
|≥5 serves/week||0.61 (0.35–1.05)||0.007|
|Non-fatal MI||Almost never||1.00|
|≥5 serves/week||0.68 (0.47–1.00)||0.04|
|Californian Seventh-Day Adventist Health Study7||26 473 (M/F)||Non-fatal MI||<1 serve/week||1.00|
|≥5 serves/week||0.49 (0.28–0.85)||<0.005|
|Fatal CHD||<1 serve/week||1.00|
|≥5 serves/week||0.52 (0.36–0.76)||<0.001|
|Physicians Health Study10||21 454 (M)||Sudden CHD death||<1/month||1.00|
|≥2 serves/week||0.53 (0.30–0.92)||0.01|
|≥2 serves/week||0.70 (0.50–0.98)||0.06|
|Iowa Women's Health Study9 12-year follow-up||34 111 (F)||Fatal CHD||<1 serve/month||1.00|
|≥2 serves/week||0.81 (0.60–1.11)||0.24|
|Iowa Women's Health Study11 15-year follow-up||31 778 (F)||Fatal CHD||<1 serve/week||1.03 (0.84–1.26)|
|≥5 serves/week||0.71 (0.55–0.91)||0.02|
|Fatal CVD||<1 serve/week||1.00 (0.86–1.17)|
|≥5 serves/week||0.72 (0.60–0.88)||0.0008|
|Study||Number of subjects (sex)||Nut consumption frequency||BMI (kg/m2)||Trends|
|Nurses' Health Study8||83 818 (F)||Almost never||24.8||BMI decreased with increasing nut consumption|
|Iowa Women's Health Study9||34 111 (F)||<1 serve/month||27.1||BMI decreased with increasing nut consumption|
|California Seventh-Day Adventist Health Study7||31 208 (M/F)||<1 serve/month||Figures not given||Statistically significant decrease in BMI with increasing nut consumption|
|Physicians' Health Study10||21 454 (M)||Rarely/never||24.9||No association between nut consumption and BMI|
|The Sun Study43||8 865 (M/F)||Rarely/never||23.6||No association between nut consumption and BMI|
|Nurses' Health Study II44||51 188 (F)||Rarely/never||24.4||Statistically significant lower risk of weight gain and obesity with nut consumption|
- 3NHMRC. A new food guidance system for Australia—foundation and total diets. Revised draft report for Public Consultation By the Dietitians Association of Australia. Released May 2010. (Available from: http://www.nhmrc.gov.au/_files_nhmrc/file/guidelines/consult/consultations/draft_foundation_total_diets_public_consult.pdf, accessed May 2010).
- 4Australian Bureau of Statistics. National nutrition survey: foods eaten, Australia 1995. 1999. (Available from: http://www.ausstats.abs.gov.au/ausstats/subscriber.nsf/0/CA25687100069892CA256888001CD460/$File/48040_1995.pdf, accessed 9 November 2011.
- 6Australian Commonwealth Department of Health and Ageing, Australian Commonwealth Scientific and Research Organisation, University of South Australia. The 2007 National Children's Nutrition and Physical Activity Survey. Australian Social Science Data Archive. Canberra, Australia: The Australian National University, 2009.
- 50The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women. Lipids Health Dis 2008; 20: 7–10., , et al.