Nuts about tree nuts! How new evidence is shaping our idea of tree nuts
If you follow a healthy lifestyle it is sure that tree nuts have come across your path in some way shape or form, as they boast an array of attractive benefits. Although, a few years ago tree nuts were considered a no-go for healthy eaters everywhere as they were considered foods high in calories and fat. This is of course true, but as more evidence becomes available it appears that incorporating tree nuts into your daily diet allows you to reap numerous health benefits that come along with the pint sized snack. The current evidence suggests that daily tree nut consumption lowers your risk of diabetes and heart disease, possibly even extending your overall lifespan. There are many nuts that fall within the greater tree nut group, some being macadamia nuts, almonds, brazil nuts, cashews, hazelnuts and chestnuts. It appears that tree nuts are fast becoming the new super food on everyone’s lips and we could not be happier! The following article will discuss macadamia nuts specifically, as well as the current evidence and industry within South Africa.
Currently, the largest tree nut crop within South Africa is macadamia nuts. South Africa falls just behind Australia as the world’s largest exporter of macadamia nuts. The favourable climate in certain parts of the country are especially ideal for macadamias and the industry within South Africa has certainly taken an upward turn in the last ten years. That being said, the industry itself is still considered quite small, having only been commercialised in Hawaii in 1950, and there is opportunity for growth within the market.
Macadamia nut farmers work incredibly hard to maintain their crops prior to their first harvest. Macadamia nut trees are only profitable after roughly 5 years and yield a small first crop, thereafter they progressively produce more nuts, reaching their maximum production at 10-15 years of age. Therefore, results are only shown years after first planting and there is a large delay between planting and harvest. Farmers put immense effort and resources toward young macadamia nut trees expecting a return many years later. Furthermore, macadamia nut trees are quite picky when it comes to their location. Macadamia nut trees grow well in a very small range of environments. Thus, there is limited ‘residential land’ when it comes to macadamia crops as they prefer high altitudes, high rainfall and temperatures that are similar to where they first originated. Although, with the expansion of the industry within South Africa it is thought that prices will become more affordable as time moves on and macadamias may become a more common food in our pantries.
Macadamia nuts are a lovely healthy snack alternative for those following an LCHF diet as they are not only delicious but are high in good fats and low in carbohydrates too! Although portion control should be considered as they are high in calories. Macadamias could possibly play a significant role in preventing the onset of multiple metabolic diseases and their benefits are only now beginning to be recognised. Regrettably, very little information is available surrounding the incorporation of macadamia nuts into an average diet, but then again that is not something to fret about as newly discovered benefits have sparked an interest in the hard nut as research on the topic of macadamia nuts is still in its juvenile stages. That allows for scope for a number of new research projects in the field that could lead to visionary outcomes. Macadamia nuts, the most common species being Macadamia integrifolia, surprisingly fall within the family Proteaceae which consists of approximately 10 species of the genus Macadamia. The most important component of macadamia nuts is their high fat content, 72% of the nut is good fats alone. The main fat composition of macadamia nuts is unsaturated, although macadamias contain a higher percentage of monounsaturated fats (MUFA) when compared with nuts, such as walnuts and pine nuts. Macadamias are also high in palmitoleic acid, an omega-7 fatty acid, which has been linked to a number of health benefits, these include preventing beta-cell apoptosis, induced by glucose or saturated fatty acids, improving cholesterol metabolism, and has beneficial effects on insulin sensitivity and overall haemostasis. Moreover, macadamia nuts have been shown to be a significant source of vitamin A, iron and contain flavonoids. Flavonoids are particularly noteworthy as they are considered antioxidants. Antioxidants are exceptional molecules that fight against oxidative stress and protect us from free radicals damage that may play a role in the onset of certain diseases, such as cancer and heart disease.
Although, with the good comes some bad. It has been previously observed that macadamias contain an anti-nutrient known as phytic acid. Phytic acid is a unique substance found in a number of plant seeds and legumes, such as chickpeas. We are aware that phytic acid has been shown to affect mineral absorption and can lead to mineral deficiencies in the diet as there is impairment of iron, calcium and zinc absorption within the gastrointestinal tract. However, macadamia nuts show significantly low levels of phytic acid and subsequently contain the least amount of phytic acid of all the nuts. This is most likely due to their hard outer shell that protects the nut from the external environment. It is unlikely that by incorporating an adequate portion of macadamia nuts into a healthy diet would have negative effects on mineral absorption. Furthermore, macadamia nuts have been known to contain a molecule known as oxalate. Oxalate is a naturally occurring molecule, found in both plants and humans, and if ingested in large amounts could lead to kidney stone formation. Luckily for the nut, it too, is low in oxalate content and is considered a good alternative to almonds when it comes to oxalate content.
A study performed by Amy E. Griel et al in 2008, where they studied the effects of a macadamia nut enriched diet on the lipid and lipoprotein profiles of mildly hypercholesterolemic men and women. This study is especially significant as few studies have been conducted using macadamia nuts as a means to evaluate their cholesterol-lowering capabilities using a recommended quantity in what is considered a standard diet. The researchers sought to replace the saturated fats commonly consumed in average diets with monounsaturated fats found in macadamia nuts. Prior research has noted that monounsaturated fats have cholesterol-lowering capabilities which could prove as a valuable resource in managing type 2 diabetes in patients suffering from the disease. Participants were randomly allocated one of the two diets, either a macadamia nut diet (MAC) diet or an average american diet (AAD) diet at the beginning of the study for a 5-week period. Both diets had the same total fat, protein and carbohydrate (CHO) profile to one another. Upon completion of the first 5-week period, the participants swapped diets for a further 5-week period. During the 5-week MAC participants were asked to consume 1.5 ounces (42.5g) of macadamia nuts per day, while the AAD was modelled after a standard American diet.
Upon completion of the study, it was observed that serum SFA had decreased in participants, while MUFAs were higher after consuming the MAC diet compared with that of the AAD. The serum PUFA concentration did not change when recorded at final screening. After the 5-week MAC diet participants experienced a lowering in serum TC, LDL-C and non-HDL-C concentrations, 4.94 +- 0.17, 3.14 +- 0.14 and 1.11 +- 0.05 in mmol/L respectively, from baseline and after AAD. After the AAD participants also experienced a decrease in LDL-C levels from baseline with a value of 3.44 +- 0.14 mmol/L. TG concentrations remained constant after the two experimental diets HDL-C concentrations were reduced in the MAC diet when compared to baseline and the AAD. There was a 9.4% reduction in TC levels and an 8,9% reduction in LDL-C concentration when compared to the control diet. in TC levels and an 8,9% reduction in LDL-C concentration when compared to the control diet. The above results from the study demonstrates that by including 1.5 ounces of macadamia nuts into a diet has a beneficial effect on TC and LDL-C concentrations by causing a significant reduction. Therefore, macadamia nuts show promising cholesterol-lowering capabilities.
A similar 2011 study by David J.A. Jenkins et al set out to access the effect of mixed nut consumption as a source of vegetable fat on serum lipids and HbA1C in type 2 diabetes (T2D) patients. Although not specifically macadamia nuts, the dietary supplement still contained macadamias as part of the portion administered to subjects. Monounsaturated fat (MUFA), commonly found in nuts, has been found to stabilize and preserve HDL cholesterol levels, as well as improve glycaemic control. The main purpose of the study was to observe the change in HbA1C. The study was conducted as a 3-month randomized parallel study consisting of 117 eligible T2D participants. The eligible participants were men and post-menopausal women with T2D, all of which had HbA1C levels between 6.5 and 8.0% at first screening. Subjects were randomly divided into three separate groups and received one of the three dietary interventions, specifically a full portion of mixed nuts (75g/day), a muffin or a half portion of each.
By the completion of the study it was observed that the mean HbA1C fell by 0,21% absolute HbA1C units in the full nut supplement group, 0,07% reduction was seen in the half-nut supplement group and a reduction of 0,05% in the muffin supplement group. Nut intake related negatively to a change in HbA1C (r= -0,20). All three diets caused an increase in HDL-cholesterol (full-nut does: 0,04mmol/L, half-nut dose: 0,03mmol/L and muffins: 0,03mmol/L). Apoprotein B (ApoB) showed a great decrease within the full-nut group when compared with the muffin group. No significant changes were observed with regards to oxidative stress, CRP levels or blood pressure. LDL levels decreased significantly in the full-nut dose group when compared to the muffin group. There was an 8.7% energy increase of MUFAs in the full-nut dose group in comparison to the muffin group. In conclusion, this study found that by replacing carbohydrate foods in one’s diet with two ounces of mixed tree nuts per day a significant improvement of glycaemic control and serum lipids in type 2 diabetic patients will be observed. Mixed nut consumption favourably influences HbA1C levels, and serum. With the prevalence of diabetes increasing globally, it may be significant to research and suggest nuts as a possible replacement for carbohydrates in a diabetic diet.]
There is a general consensus that PUFAs negatively affect our health and we can all come to the conclusion that we should stay away from them, but how do we decide which oils we should include in our diets? There are countless different oils and fats on the market which could make it difficult to decide which oils/fats should be included in your daily diet and at what amounts. The majority of products all promote varying health advantages, yet give very little guidance has been given as to how much should be included in your diet to reap these benefits. Following the steady stream of new evidence suggesting multiple health benefits of macadamia nut inclusion in diets, The Noakes Foundation is embarking on an exciting new research study. Our endeavour will take a look at oil supplementation, its place within an LCHF diet and how it may affect certain health markers of interest. The Noakes Foundation is calling upon all those interested that would like to take part in a pilot study which will commence early next year. If you are interested in learning more about the study and follow a healthy lifestyle please keep a look out for our call for participants soon where we will include additional information pertaining to the study and the necessary criteria! It is in the hope that by collating the current available research on the benefits and composition of certain nut oils and conducting the aforementioned study The Noakes Foundation will be able to open new avenues of research in the field, possibly leading to greater discoveries thereafter and aiding the broader community in making informed healthy diet choices.
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“A PROFILE OF THE SOUTH AFRICAN MACADAMIA NUTS MARKET VALUE CHAIN.” The South African government, 2012, https://www.daff.gov.za/docs/amcp/macadamia2012.pdf. Accessed 7 December 2020.
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“Why are macadamia nuts so expensive?” Nutcellars, https://www.nutcellars.com/blog/why-are-macadamia-nuts-so-expensive#:~:text=One%20of%20the%20main%20reasons,delay%20from%20planting%20to%20harvest.&text=This%20means%20that%20farmers%20need,any%20return%20on%20their%20investment. Accessed 7 December 2020.
About the author
Shannon Mace has a BSc degree in Human Life Sciences from Stellenbosch University, she majored in biochemistry and physiology. She has a keen interest in metabolic physiology and hopes to further her studies in the subject. Shannon has joined The Noakes Foundation as a researcher, as well as an administrator. She looks forward to helping the foundation promote healthier living and happier lifestyles.