Recent research is throwing new light on the health benefits of nuts.
So lets look at what makes nuts healthy and how much we need to eat in order to enjoy their health benefits?
What is a nut?
According to Wikipedia, “culinary nuts are dry, edible fruits or seeds, usually, but not always, with a high fat content. Nuts are used in a wide variety of edible roles, including in baking, as snacks (either roasted or raw), and as a flavouring”. 1
- True, or botanical nuts: dry, hard-shelled, uncompartmented fruit that do not split on maturity or release seeds e.g. acorns, chestnuts, hazelnuts etc.
- Drupes: fleshy fruit surrounding a stone, or pit, containing a seed e.g. almonds, cashew, coconut, pecans, pistachio and walnuts.
- Gymnosperm seeds: naked seeds, with no enclosure e.g.pinenuts.
- Angiosperm seeds: unenclosed seeds within a larger fruit e.g. peanuts
The nutritional value of nuts
- Nuts are very nutrient dense containing some protein, fat (particularly polyunsaturated fat), dietary fibre, calcium, vitamins and minerals and are naturally low in sodium.
- To gain the most benefit from nuts, it is important not to add salt, sugar or other fats, so unprocessed nuts are best.
- Raw nuts should be consumed with their skin on, as most of the antioxidants and phytochemicals are located in the soft outer shell of the nut.
What are the nutritional benefits of eating nuts?
Here are just a few of the results from studies showing that tree nuts (almonds, Brazil nuts, cashews, hazel nuts, macadamia, pecans, pine nuts, pistachios and walnuts) are healthy to eat.
A study that looked at 13,292 men and women (19+years) participating in the 1999-2004 National Health and Nutritional Examination Surveys (NHANES) found over a 24 hour recall period, those participants who consumed unsalted tree nuts > ¼ounce /day experienced the following benefits:
- 5% lower prevalence of metabolic syndrome (the name given to a group of risk factors that occur together and increase the risk for coronary artery disease, stroke and Type 2 diabetes.2
- Lower levels of C-reactive protein, a marker for inflammation which is associated with atherosclerosis and artery disease.3
- A lower prevalence of:
- abdominal obesity
- high blood pressure
- high fasting glucose (blood sugar)
- low high density lipoprotein-cholesterol levels (i.e. ‘good cholesterol’)
The NHANES study2 concluded that the benefits were greatest when nuts were eaten as part of a healthy diet that included:
- Whole grains
- Less saturated fats
- Low salt
- Fewer calories from solid fats, alcohol and added sugars2
NOTE: these benefits were achieved with only > ¼ ounce nuts /day
Researchers at Andrews University have found that students who had eaten walnuts daily as one of the main ingredients in banana bread performed better on tests that measure inferential reasoning i.e the ability to judge the accuracy of statements made when reading an article, paper or other source.4
Protecting bone health
Walnuts may also decrease the breakdown of bone. One study in Penn state found that higher consumption of the essential fatty acid alpha-linolenic acid (ALA), that is plentiful in walnuts, leads to a reduction in bone turnover, and a shift in the balance of bone degradation/ formation towards formation.4
Walnuts rank above peanuts, almonds, pecans, pistachios and other nuts as they contain almost twice as many antioxidants. Only 7 walnuts a day are needed to enjoy the health benefits.5
Studies have considered the role of nuts in weight control offering several reasons why the regular consumption of nuts may not result in weight gain.
Here are some of those reasons:
- Nuts are filling because they are high in protein and dietary fibre. While they contain too little carbohydrate to measure their glycaemic index nuts appear to slow the digestion of carbohydrate rich foods. These factors along with their crunchy nature stimulates, during chewing, hormones like cholecystokinin which aids satiety.
- Nut may increase metabolism . It is now thought that nut consumption may lead to an increase in energy expenditure as the high unsaturated to saturated fat ratio in nuts may increase resting metabolic rate (RMR).
- Reduced energy absorption. Some research suggests that despite their high fat nature the fat found in nuts may not be highly bioaccessible. Meaning that some fat may be lost in faeces rather than being available as an energy source.
With these things in mind one research project compared the consumption of hazel nuts with other high fat snacks (chocolate and potato crisps) on the health of 118 non obese subjects. They looked at body weight and composition, blood lipids and lipoproteins, RMR, appetite indices and diet quality. Interestingly after 12 weeks they found no difference in the outcomes measured between groups except for diet quality which was significantly higher in the nut group despite the fact that weight was maintained.6
Problems associated with nut research in the past
Concern regarding research claiming health benefits of nut eating in the past have been critical of the methodology used, that sample sizes were small or over short duration. Body weights were often self reported, recruitment methods seldom randomized and studies can be financed by industrial companies such as Hershey or nut producers.7
Nut and Food Allergy
Allergies can be triggered by a number of foods but the most common are peanut and tree nut.
Tree nuts include: cashew, almond, Brazil, hazelnut, walnut, pecan and pistachio.
Peanuts are a legume and so allergy sufferers may also need to be careful when eating legumes such as peas, beans and lentils.
Reactions are usually mild in the form of hives, eczema and vomiting. Those more sensitive may have difficulty breathing experiencing an anaphylactic reaction inducing asthma, throat swelling and a drop in blood pressure 8
Recommendation for use
- If you suspect you have an allergy to nuts consult your doctor who may refer you to an allergist and/or laboratory for testing.
Read labels carefully, avoid all foods and products that “contain” or “may contain nuts”. Also be aware that cross contamination can occur during manufacture; retailing and food preparation when nut fragments may be transferred on equipment, utensils and during handling.
- For those people who are of a healthy body weight and non-allergic the use of nuts as a snack or in salads or main meal dishes should do no harm.
However it is important to watch the other ingredients accompanying the nuts which may contribute to weight gain such as butter and sugar found in. e.g. muesli bars, biscuits, bliss balls, nought, cakes, confectionery and slices.
- People who have very high energy needs such as athletes or workers involved in physically demanding occupations will find nuts a healthy addition to their diet (but should still note comments above).
- If overweight or obese then limit nuts to 30g per day e.g. 2 brazil nuts each day will confer health benefits plus help you to meet your daily needs for selenium. Discuss your needs with your Dietitian.
- Remember nuts alone won’t make you healthy unless taken as part of a healthy diet as outlined in the NHANES study.
- If you are having 3 red meat ( e.g. beef, pork or lamb), 2 white (e.g. fish or chicken) and 2 non meat meals ( e.g.vegetarian dishes such as based on egg, cheese, bean or lentils) per week then the nuts could be included in the non meat meal dishes. See our recipe for Spinach and walnut lasagna.
- As the fat in nuts can go rancid it is important to buy nuts in small amounts from stores where there is a high turnover to assure freshness. Use nuts within the use by day period and remember to store nuts in a cool, dry and dark place
- Nut definition: http://en.wikipedia.org/wiki/List_of_culinary_nuts
- O’Neil CE, Keast DR , Nicklas TA, Fulgoni VL, 111,2011. Nut consumption is associated with decreased health risk factors for cardiovascular disease and metabolic syndrome in U.S adults:HNANES 1999-2004. J Am Coll Nutr. 30:502-510.
- O’Neil CE, Keast DR, Fulgoni VL, Nicklas TA, 2010. Tree nut consumption improves nutrient intake and diet quality in US adults:an analysis of National Health and Nutritional Examination Survey (NHNES) 1999-2004. Asia PacJ CLin Nutr.19(1):142-150.
- Leong K, “Will eating walnuts give you more brain power?” Yahoo News. Sept 28,2011 http//voices.yahoo.com/will –eating-walnuts-give-more-brain-9157073.html?cat=5
- 7 Walnuts a Day Deliver Health Benefits,” Health News, March 28,2011. http://www.upi.com?Health_News/2011/03/28/7-walnuts-a-day-deliver-health-benefits?UPI-93441301365744/.
- Tey Sl, Brown R, Gray A, Chisholm A, Delahunty C, 2011. Nuts improve diet quality compared to other energy-dense snacks while maintaining body weight. Journal of Nutrition and Metabolisk.doi:10.1155/2011/357450
- What are the health effects related to consumption of nuts? 2012 USDA Evidence Analysis Library. Printed on:06/23/12
- Allergy NZ; Peanut and tree nut allergy: http://www.allergy.org.nz/A-Z+Allergies/Food+allergy/Peanut+and+tree+nut+allergy.html