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What's the Latest on Nuts and Health?(date issued June 2005) The following series of questions and answers describe current knowledge of the health effects of nuts, including peanuts. (Although they have similar nutritional characteristics to nuts, peanuts are actually legumes rather than true nuts). SummaryFor the vast majority of people, nuts are nutritious, health-promoting foods. When eaten in moderation (25–50 grams per day, a small handful) as part of a varied, nutritious diet, they may assist in reducing the risk of heart disease and diabetes, without contributing to weight gain. Peanuts, which are technically ‘legumes’ rather than nuts, have similar nutritional composition and health effects to those of ‘real’ nuts. Coconuts, which technically are also not ‘nuts’, do not have the same types of fats as true nuts, and may not confer the same health benefits. For people who are allergic to a particular nut (or group of nuts), any exposure to those nuts is potentially very dangerous. Because nuts are generally very rich in fat, it is important to substitute nuts for other, less health-promoting foods, rather than simply add them to the diet. 1. Okay, a peanut isn’t a true nut; so what exactly are ‘nuts’?The Macquarie Dictionary defines ‘nut’ as “a dry fruit consisting of an edible kernel or meat enclosed in a woody or leathery shell”. The Macquarie also states that botanically, a nut is a “hard … one-seeded fruit, as in chestnut ...” The peanut, on the other hand, belongs to the same botanical family as peas and beans, making it technically a ‘legume’ rather than a nut. However, the nutritional composition of the peanut is much closer to that of true nuts than to peas or beans, so much of the following discussion applies equally to peanuts as to almonds, Brazil nuts, cashews, chestnuts, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios and walnuts. Also, while the coconut is commonly referred to as a ‘nut’, the International Nut Council does not recognise it as such. 2. What nutrients do nuts provide?Rather unusually for foods of plant origin, nuts are generally very rich in protein and also contain large quantities of fat (with the sole exception of chestnuts, which have little protein or fat, and provide mostly carbohydrate). This means that nuts are included in the ‘protein’ food group along with meat, fish, poultry, eggs and legumes. Although nuts are generally high in fat, this fat is mostly ‘monounsaturated’ or ‘polyunsaturated’. (However, the fat in coconuts—commonly thought of as being nuts, but not accepted as such by the International Nut Council—is mostly ‘saturated’ fat). The health significance of these types of fat is discussed in the answer to Q. 3 below. The total levels and the types of fat in most nuts and peanuts are shown in the following table. TABLE: Fat composition of nuts and peanuts (from Sabate, 2003)
It should also be mentioned that nuts are often sold with added salt. The vast majority of Australians already eat more salt than is good for them (for more on this see the FAQ on Salt, URL: http://www.nutritionaustralia.org/Food_Facts/FAQ/summary_salt_faq.asp) so this extra salt is nutritionally inappropriate. However, it is gradually becoming easier to find raw or dry roasted pre-packaged nuts that do not contain added salt or fats. Nuts are also often available ‘in the shell’, without added salt. These nuts can also be bought in bulk so represent good value for money. However, because most nuts contain small amounts of polyunsaturated fats, they do not have a long shelf life. Rancidity of the polyunsaturated fats can occur, leading to off-flavours. One possible way of overcoming this is to buy nuts in bulk, transfer them to smaller bags, and refrigerate or freeze them for future use. Peanut butter is also often sold with added salt and/or sugar. Careful reading of the labels in the supermarket (perhaps in the ‘health food’ section) may allow you to identify peanut butter or other nut butters with no added salt or sugar. Perhaps even better, some health food shops will make peanut (or other nut) butter while-you-wait, using fresh nuts with no added salt, sugar or oil (while most commercial brands also have added oil). This ‘dry-ground’ nut butter provides all the benefits of the nuts, without the extra ingredients of low nutritional value. Nuts are also quite good sources of dietary fibre and a wide range of essential nutrients, including several B group vitamins, vitamin E, minerals such as iron, zinc, potassium and magnesium, and antioxidants. Because nuts come from a variety of plant species, each type of nut has its own unique nutritional advantages. As examples, Brazil nuts provide large quantities of thiamin (also known as vitamin B1) and an essential trace element called selenium—in fact just one Brazil nut can provide your entire day’s requirement for selenium; cashews are moderately rich in iron and zinc; peanuts are a good source of niacin (vitamin B3); almonds contain worthwhile quantities of calcium, riboflavin (vitamin B2) and vitamin E; and pistachios provide plant sterols (which help to reduce blood cholesterol by preventing cholesterol absorption from the gut). As with food generally, ‘variety is the spice of life’. That is, it is better to eat a variety of nuts—and so obtain a wide range of nutrients—than to eat just one or two preferred types. 3. If nuts are high in fat, does that mean they are bad for heart health?Based on both the composition of the fats (mainly monounsaturated and polyunsaturated) and the results of studies comparing heart disease rates among people who eat nuts with those who do not, the answer seems to be a resounding ‘no!’ In fact, it appears that consuming about 25–50 grams of nuts per day (a small handful) provides a similar level of protection against heart disease as that provided by cholesterol-lowering drugs. It has been known for many years that saturated fats are the major dietary ‘culprit’ in terms of increasing heart disease risk. Monounsaturated and polyunsaturated fats are regarded as generally heart-healthy. Because true nuts and peanuts (but not coconuts) are low in saturated fats, it is not surprising that they seem to be protective against heart disease, especially when they are eaten in place of saturated fats. (Replacing saturated fats with nuts has been shown to result in a drop of approximately 50% in the risk of heart disease). Although this heart-friendliness may not apply to coconuts, studies strongly suggest that walnuts, macadamias, peanuts, cashews, pecans, pistachios and almonds are all good for the heart when eaten in moderation as part of a nutritious and varied diet. 4. What about diabetes—is there an effect of nuts on the risk of developing type 2 diabetes?The situation seems to be similar for diabetes as for heart disease—nuts may be protective. For example, a large study found that women who ate about 30 grams of nuts per day for five days a week had about 30% less risk of developing diabetes compared to those who ate few or no nuts. This effect was attributed at least partly to the high levels of monounsaturated and polyunsaturated fats, which are believed to be good for insulin sensitivity, in addition to their positive effects on blood cholesterol. And processed forms of nuts were also found to be beneficial—women who frequently ate peanut butter had 20% less risk of developing diabetes compared to those who ate little or no peanut butter. These ‘associations’ don’t prove cause-and-effect—it may be that the consumption of nuts is a marker for some other component of diet or lifestyle that actually confers the protection. But the associations at least suggest that nut consumption doesn’t promote diabetes, and may even be protective. 5. Should I avoid nuts if I don’t want to put on any more weight?It seems strange that a food that is very rich in fat might be seen as suitable for people who may be carrying some excess body fat. Nevertheless, several studies have indicated that moderate intake of nuts (25–50 grams per day, a small handful) is not associated with a tendency to gain weight. In fact, although the evidence isn’t conclusive about this, consuming nuts may assist slightly with actual weight loss. If this turns out to be correct, it may be because nuts have a high satiety value (i.e. they make you feel ‘full’ for a relatively low kilojoule intake). If you decide to increase your consumption of nuts, to make sure your kilojoule intake doesn’t increase, it is important to substitute nuts for less nutritious foods rather than simply ‘add’ them to your diet. As examples, nuts could replace some processed meats, refined cereal foods such as white bread, fatty and/or sugary snack foods, fried takeaways, and so on. 6. Are there any special health problems associated with nuts?Most nuts are not associated with any health problems in the vast majority of people. However, nut allergies are a major cause for concern in a small proportion of the population. Some people are allergic to ‘tree nuts’ ( almonds, Brazil nuts, cashews, chestnuts, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts ), some are allergic to peanuts, and a few unfortunate people are allergic to both tree nuts and peanuts. At least in terms of the number of deaths it causes, nut allergy is probably the most serious food allergy. It has been reported that peanut allergy kills about 100 people a year in the United States alone, and its incidence appears to be increasing—one study found that (self-reported) peanut allergy among American children doubled from 1997 to 2002. A New Zealand study reported that at least 0.6% of the general population is allergic to one or more tree nuts, and peanut allergy has been reported to affect 1.9% of Australian infants. Although probably no more than about 1% of people are allergic to peanuts and/or tree nuts, because of the high risk of ‘anaphylactic shock’ (collapse, with possibly fatal consequences) it is essential that people with allergies to nuts avoid all contact with those nuts and products that might contain those nuts. It is also strongly recommended that people with nut allergies carry adrenaline (also known as epinephrine), the medication that will be prescribed by their doctor for managing a severe reaction. 7. You’ve mentioned that a daily intake of 25–50 grams of nuts seems to be health promoting; how many nuts does this weight correspond to?A health-promoting daily intake of 25–50grams of nuts is about one small handful. This corresponds to approximately 25–50 almonds, 12–24 cashews, 5–10 Brazil nuts, 30–60 shelled peanuts, or 12–24 walnuts. As mentioned in the answer to Q. 5, simply adding nuts to your existing diet is not appropriate. If you do not already eat nuts, but you decide to include them in your diet in future, this should be at the expense of other, less nutritious foods. In addition to snacking on nuts, you can also use them in cooking, so you share the benefits with friends or family. Adding them to your favourite stir-fry or salad, crushing them on desserts, and adding slivers to breakfast cereal will improve not only the taste and texture of these meals, but also their nutritional value. For other innovative suggestions on how nuts can be added to your diet, go to: http://www.nuthealth.org/consumer.php3?page=1 Reference (for Table): Sabate J. Nut consumption and body weight . Am J Clin Nutr. 2003 Sep;78(3 Suppl): 647S-650S. Further reading: Nuts for Life is an education initiative of the Australian Tree Nut Industry to raise the awareness of the health benefits of tree nuts. URL: www.nutsforlife.com.au Back to Frequently Asked Questions Index |