From the Rare Fruit Club WA
by John H. Weisburger
Macadamias
Australia's contribution to the world's fruits and nuts
"Eat to Live, Not Live to Eat"
Considering the thousands of edible tropical and
sub-tropical fruits known worldwide, the USDA has suggested that only
300 of these are commercially important and less than 100 contribute to
most production and consumption. Of fruits from Australia, the
macadamia nut is the only one that makes these lists. Possible reasons
for this laggard performance include firstly that our continent is the
driest and has been relatively isolated botanically for a long time. As
a consequence we don't have anything like the diversity and profusion
of edible and palatable species found in Asia and the Americas.
Secondly, our indigenous people have had a nomadic lifestyle for
thousands of years that did not gradually improve the stock by
selection of occasional superior trees as happened more often
elsewhere. As a result, our limited native bush foods have remained in
their original unimproved forms, and consumption of the best of them
remains largely at the fringes of society.
However despite these
negatives, numerous surveys and personal evaluation have usually judged
the macadamia to be the tastiest of all the commercial nuts. They taste
good raw and even better roasted, but most of the world's crop is eaten
in more processed forms such as chocolate-coated kernels,
nut-impregnated chocolates, muffins, pies etc. It was the Hawaiians who
first realised their commercial potential, did the development work on
them over several decades to produce superior cv's and then built up a
successful industry. Only then did we belatedly decide to get
operations going here on our own native plant!
Macadamias have
an extremely strong shell which is more difficult to crack than other
tree nuts. For the home user this usually means that many kernels are
fractured during preparation. Like all nuts, un-broken kernels command
higher retail prices than fragments and commercial crackers can give a
better proportion of unbroken nuts than that achieved by the home-user.
As with cashews which have a toxic oil removal problem, much of the
high cost of purchase is due to quality kernel preparation. However, if
you only want to savour a few a day, the high retail price provides a
good incentive to grow your own, given a few broken kernels is really
neither here nor there – you still get to enjoy these delicious things
and they store quite well in-shell if kept dry.
So macadamias
are almost universally recognised as strong players on the pleasure
front. But do they also have favourable nutritional qualities that can
be of benefit in our current Western dietary habits which underlie so
many chronic disease problems, since many of these have progressed to
epidemic proportions? The following is a summary of a study (J.
Nutrition (2003) 133: 1060–1063) by a research group at the University
of Newcastle NSW illustrating that macs have substance and aren't just
a 'pretty face'. It concerns unhealthy blood cholesterol levels which
predispose to cardiovascular disease (CVD), the biggest cause of
mortality in Australia.
| This study was conducted to assess
the cholesterol-lowering potential of macadamia nuts. Seventeen
hyper-cholesterolemic men (mean age 54 y) were given macadamia nuts
(40–90 g/d), equivalent to 15% energy intake, for 4 wks. Plasma total
cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and
homocysteine (a CVD risk factor) concentrations and the fatty acid
composition of plasma lipids were determined before and after
treatment. Plasma monounsaturated fatty acids (MUFAs) were elevated
after intervention with macadamia nuts. Essential polyunsaturated fatty
acid concentrations(n-6 and n-3 PUFAs) concentrations in plasma were
unaffected by macadamia nut consumption. Plasma total cholesterol and
LDL-cholesterol concentrations decreased by 3.0 and 5.3% respectively,
and HDL cholesterol levels increased by 7.9% in these
hyper-cholesterolemic men after macadamia consumption. Plasma
triglyceride and homocysteine concentrations were not affected by
treatment. Macadamia consumption was associated with a significant
increase in the relative intake of MUFA and a reduced relative intake
of saturated fatty acids and PUFA. This study demonstrates that
macadamia nut consumption as part of a healthy diet favourably modifies
the plasma lipid profile in hyper-cholesterolemic men despite their
diet being high in fat. |
The
quantity of nuts used in this study is higher than most people would
consume per day but other studies since have considered more reasonable
lower levels with comparable results. Although the 'bad'
LDL-cholesterol only decreased by 5.3% on average, importantly the
'good' HDL-cholesterol increased by the larger margin of 7.9%, so that
the more relevant ratio for predicting health benefits, namely LDL/HDL,
changed to a far greater degree than either alone. Macadamias have the
highest fat content of all the important tree nuts (76%) and 80% of
this is MUFAs. Collectively, all these nuts have qualitatively similar
effects on CVD and underlying risk markers, with the relative magnitude
of effects depending on their particular makeup. No one of them is
superior in all nutrient components so that the best strategy for
health benefits is to eat mixed nuts rather than believing that any one
of them is clearly superior. Three pillars of modern nutrition are
balance, moderation and variety, and simplistic belief in the magic or
sufficiency of 'super foods' that should be single-mindedly consumed is
flawed.
To illustrate the varying strengths of nuts and the lack
of any that are tops all round, consider how macadamias stack up
against some of the others regarding familiar macro- and
micro-nutrients (expressed per 100g edible fresh food): they have 7.9g
protein cf 25.8g in peanuts, 6g fibre cf 10.4g in hazelnuts, 12.1g
saturated fat cf 3.9g in almonds, 58.9g MUFA cf to 8.9g in walnuts,
1.5g PUFA cf 47.2g in walnuts, 1.3g n-6 essential fatty acids (eg
linoleic acid) cf 20.6g in pecans, 0.2g n-3 (alpha-linolenic acid) cf
9.1g in walnuts, 11mcg folate cf 145mcg in peanuts, 0.54mg vitamin E cf
27.1mg in almonds, 85mg calcium cf 248mg in almonds, and 130mg
magnesium cf 376mg in brazil nuts. With other less familiar plant
phytochemicals, macadamias have roughly half the level of phytosterols
cf pistachios and peanuts, and total antioxidant phenols in pecans is
28 times that in macadamias. All nuts including macadamias are very
good nutrient-rich foods, and positive health effects that have been
reported in addition to the study above on CVD risk factors include
type 2 diabetes, reduction in overweight and obesity, gall stones,
hypertension, cancer and inflammation.
Fruits and nuts may be
processed into various forms for a number of reasons such as cultural
practices, improved storage properties, improved palatability and
taste, aesthetics and nutrition. If nutrition is important to you with
the nuts you eat, then it should be recognised that preparation and
processing can have a considerable influence. Most fruits have an
unequal distribution of nutrients throughout the edible parts, usually
with higher levels found towards the exterior. Simply removing apple
skins before eating (eg for cooking in apple pie where heat/time causes
its own additional losses) can result in loss of over 90% of
phytochemical antioxidants.
With nuts this surface concentration
can be similarly extreme eg in walnuts 95% of antioxidants are in the
brown seed coat, almonds are often blanched to remove their brown coat
for aesthetic reasons and so lose 80% antioxidant capacity, and peanuts
minus their red-brown seedcoat lose 70%. Then once the kernel is
isolated, simple dry roasting can further degrade nutrition (although
usually enhancing flavour) eg with pistachios the loss can be 44%. More
extensive processing into popular products such as peanut butter loses
another 50%. As with many foods, raw is frequently best nutritionally
unless there's a specific reason to modify, eg inhibit, microbial
spoilage, reduce anti-nutrient factors or soften tough fibrous tissue.
Back to
Smooth Shell Macadamia Page
Rough Shell Macadamia Page
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