Otago University Hazelnut Research :- Dr. Alexandra Chisholm's presentation to HGA Field day, March 2018

The latest in a Nutshell’

Hazelnut Summer Field Days 17 Feb 2018, Alexandra.

Speaker: Alexandra Chisholm


The Nut Research Group* at the Department of Human Nutrition, University of Otago has been involved with research into the health benefits of hazelnuts for more than 10 years. Last year we published eight papers, detailing our research.  The health benefits of nuts are being recognised world wide, particularly the effects on cardiovascular disease (CVD), which contributes to around 40% of deaths in NZ. Observational studies investigate what is going on at the population level & need to follow very large groups of people over many years. This is how the Adventist Health Study ‘uncovered’ the heart health benefits of eating nuts regularly. Intervention research can use smaller groups of people who receive nuts, usually compared to some other food, as part of a research study.  For example our feeding study (all food provided) examined adding either 30g / day nuts or seeds to the diet of post menopausal women with type 2 diabetes (DM) over 3 weeks. Interestingly we saw positive benefits for both nuts and seeds. Nuts had a better effect on HDL cholesterol and seeds on LDL cholesterol, both key indicators of risk for cardiovascular disease. We have just finished a study with a larger group of women with type 2 DM who have been adding 30g / day hazelnuts or sunflower seeds, or some of both to their diets over 12 weeks. There is also a control group (no nuts or seeds supplied). We are investigating effects on blood cholesterol, blood glucose, body weight, plasma vitamin E and testing for markers of inflammation. Nuts are high in energy and rich in healthy fats, protein, fibre, minerals and vitamins. The fat in all nuts except walnuts is richer in mono-unsaturated fatty acids (like the fat in olive oil) whereas seeds and walnuts are higher in poly-unsaturated fats. The protein and amino acids in nuts may help to reduce inflammation and aid in lowering blood cholesterol. Nuts also contain phyto-sterols, dietary fibre and anti-oxidants, which help to combat inflammation.  Given their beneficial composition –a quick way to improve diet quality is to substitute unroasted, unsalted nuts for less healthy foods. One antioxidant compound found in high amounts in hazelnuts is proanthocyanidin.  It is concentrated in the pellicle thus removing the skin could result in the loss of greater than 50% of the antioxidants present in the nuts- so more benefit from un-blanched nuts. A project in our department showed that the current fashion of soaking nuts to improve their digestibility does not have any beneficial effect on digestion & may leach out micronutrients. The Adult Nutrition Survey showed that percentage of the population who eat any nuts was low at 28.8% and the amount eaten by those who eat nuts regularly was 18g/day.  Most nuts were eaten as an ingredient in some other food, followed by nut butters then whole nuts. A recent interest of our group has been to explore the patterns & predictors of nut consumption amongst the general population. Taste is the biggest plus while concerns about chewing nuts or dental problems may make people wary of eating nuts. We also investigated the recommendations around eating nuts, made by three groups of health professionals. Dietitians were more likely to recommend patients increase consumption of nuts than general practitioners and practice nurses. Most health professionals recommended raw nuts & the most popular recommendations were almonds, Brazil nuts and walnuts. Dietitians recommended around 30g/d, whereas both general practitioners and practice nurses recommended around 20g/d. There were still concerns about weight gain though this has not been demonstrated, as well as issues regarding allergies and cost.

Note: All nuts are purchased for the nut research carried out at Otago University. We have bought all our hazelnuts from Uncle Joes Walnuts & Hazelnuts in Marlborough.

*The Nut Research Group: Associate Professor Rachel Brown, Dr Agnes Siew Ling Tey, Dr Alexandra Chisholm, Mr Andrew Gray, Emeritus Professor Christine Thomson.


Current nut recommendation practices differ between health professionals in New Zealand. Brown RC, Gray AR, Yong LC, Chisholm A, Leong SL, Tey SL.Public Health Nutr. 2018 Apr;21(6):1065-1074. doi: 10.1017/S1368980017003469. Epub 2017 Dec 4.

Barriers to and facilitators and perceptions of nut consumption among the general population in New Zealand.Yong LC, Gray AR, Chisholm A, Leong SL, Tey SL, Brown RC. Public Health Nutr. 2017 Dec;20(17):3166-3182. doi: 10.1017/S1368980017002464. Epub 2017 Oct 2.

Nut consumption is associated with better nutrient intakes: results from the 2008/09 New Zealand Adult Nutrition Survey.   Brown RC, Tey SL, Gray AR, Chisholm A, Smith C, Fleming E, Parnell W. Br J Nutr. 2016 Jan 14;115(1):105-12. doi: 10.1017/S0007114515004122. Epub 2015 Oct 20.


Walnuts shown to activate brain region involved in appetite control

In a Nutshell
Controlled portions of nuts such as walnuts are often recommended for patients with obesity and type-2 diabetes because they are thought to discourage overeating by promoting feelings of fullness. How the nuts might do so, however, remains murky.

In a small new brain-imaging study partially sponsored by the California Walnut Commission, researchers at Harvard Medical School and Beth Israel Deaconess Medical Center have found that consuming walnuts activates an area in the brain associated with regulating hunger and cravings.

The findings, published online in the journal Diabetes, Obesity and Metabolism, reveal for the first time the neurocognitive impact these nuts have on the brain.

“We know people report feeling fuller after eating walnuts, but it was pretty surprising to see evidence of activity changing in the brain related to food cues, and by extension what people were eating and how hungry they feel,” said the study’s first author, Olivia Farr, HMS instructor in medicine in the Division of Endocrinology, Diabetes and Metabolism at Beth Israel Deaconess.

Trying to determine exactly how walnuts quell cravings, Farr and colleagues, including senior investigator Christos Mantzoros, HMS professor of medicine and director of the Human Nutrition Unit at Beth Israel Deaconess, used functional magnetic resonance imaging (fMRI) to observe how consuming walnuts changes brain activity.

The scientists recruited 10 obese volunteers to live in Beth Israel Deaconess’ clinical research center for two five-day sessions. The controlled environment allowed the researchers to keep tabs on the volunteers’ precise nutritional intake rather than depending on volunteers’ often unreliable food records—a drawback to many observational nutrition studies.

During one five-day session, the volunteers consumed daily smoothies containing 48 grams of walnuts—the serving recommended by the American Diabetes Association dietary guidelines. During their other stay, they received a walnut-free but nutritionally comparable placebo smoothie, flavored to taste the same as the walnut-containing smoothie.

The order of the two sessions was random, meaning some participants consumed the walnuts first and others consumed the placebo first. Neither the volunteers nor the researchers knew during which session they consumed the nutty smoothie.

As in previous observational studies, participants reported feeling less hungry during the week they consumed walnut-containing smoothies than during the week they were given the placebo smoothies. fMRI tests administered on the fifth day of each session gave the research team a clear picture as to why.

While in the machine, study participants were shown images of “desirable” foods like hamburgers and desserts, neutral objects like flowers and rocks, and “less desirable” foods like vegetables.

When participants were shown pictures of “highly desirable” foods, fMRI imaging revealed increased activity in a part of the brain called the right insula after participants had consumed the five-day walnut-rich diet compared to when they had not.

“This is a powerful measure,” said Mantzoros. “We know there’s no ambiguity in terms of study results. When participants eat walnuts, this part of their brain lights up, and we know that’s connected with what they are telling us about feeling less hungry or more full.”

The researchers said this area of the insula is likely involved in cognitive control and salience, meaning that participants were paying more attention to food choices and selecting the “less desirable” or healthier options over the “highly desirable” or less healthy options.

Farr and Mantzoros next plan to test different amounts, or dosages, of walnuts to see whether more nuts will lead to more brain activation or if the effect plateaus after a certain amount. This experiment will also allow researchers to test other compounds for their effect on this system.

Similar studies could reveal how other foods and compounds, such as naturally occurring hormones, impact the appetite control centers in the brain.

“From a strategic point of view, we now have a good tool to look into people’s brains—and we have a biological readout,” said Mantzoros. “We plan to use it to understand why people respond differently to food in the environment and, ultimately, to develop new medications to make it easier for people to keep [excess] weight down.”

The study was supported by Harvard Clinical and Translational Science Center grant UL1RR025758 from the National Center for Research Resources at the National Institutes of Health and by NIH grant K24 DK081913. The California Walnut Commission (CWC) supported the study through an investigator-initiated grant. The CWC had no role in study design or conduct; data collection, management, analysis or interpretation; or manuscript preparation, review or approval.

Adapted from a Beth Israel Deaconess news release.

Meatless Mondays trend

 Cutting back on meat consumption has numerous advantages, from your physical health to the well-being of the environment

It’s well known that high consumption of red meat can lead to major health issues such as diabetes, stroke, heart disease and cancer. Studies like the 2012 one out of the  Harvard School of Public Health  shows that replacing one serving of red meat weekly with one serving of nuts reduces mortality risk by 19%.

Global health can also be improved with the replacement of meat by nuts and grains.
UN studies show factory farmed animal production causes “an even larger contribution" to climate change than the transportation sector worldwide.”

A University of Oxford study out in march last year found that widespread adoption of vegetarian diet would cut food-related emissions by 63% and make people healthier too. A global switch to diets that rely less on meat and more on fruit and vegetables could save up to 8 million lives by 2050, reduce greenhouse gas emissions by two thirds, and lead to healthcare-related savings and avoided climate damages of US $1.5 trillion

Facts like this have driven the global movement of “Meatless Monday” with a simple message: Once a week, cut the meat. Started by the Johns Hopkinds Bloomberg School of Public Health it’s now entering its second decade and is embraced in 36 countries.
 Nuts, seeds and beans along with an increased consumption of fruits and vegetables will provide a well balanced meal plan on the days you go meatless.

For those dropping meat from a meal or so a week there is no worry about protein but for vegetarians counting purely on the protein from nuts to meet your protein needs, consume either legumes or dairy products as well, as these are complementary proteins which when combined with nuts contain all of the essential amino acids. You don't need to consume complementary proteins during the same meal, just at some point during the same day.  


A guide to growing Hazelnuts in New Zealand

Hazelnuts are still a niche product in New Zealand but they have the potential to be the country’s main nut crop and you won’t meet anyone who loves them more than hazel researcher and grower Murray Redpath.

Words Murray Redpath & Nadene Hall  -  Featured in  NZ Lifestyle Block magazine.

Corylus avellana

Commercial varieties: Whiteheart, Barcelona, Tonda Romano, Tonda di Giffoni

In-shell varieties for market: Butler, Campanica, Ennis, Lansing

Best growing areas: potentially nationwide, but most crops currently mostly planted in Canterbury, Coastal Otago and Southland

Prospects: potentially New Zealand’s main nut crop, currently covers only 400ha

Potential markets: China, Australia, New Zealand, USA, Europe, Asia, Japan

Economic numbers: mature orchards should yield 1.5-3 tonnes/hectare, or around $4000-$7000 per tonne

Soil requirements: tolerant of most soils, ideally a fertile well drained silt or clay loam

Climate requirements: requires good shelter, similar chilling requirements to apples, tolerant of frosts down to –7°C, rainfall ideally 800-1000mm, does not like low humidity and high temperatures

Pests/diseases: big bud mite, hazel leaf miner, green shield beetle, aphids, lemon tree borer, hazel blight

Harvesting: nuts fall to the ground, harvested with vacuum harvesters, small blocks can use nets.

One of the best things about hazelnuts is they grow best where other nut crops do not.

New Zealand is a land ideally suited to hazels. It is a plant adapted to moist, sheltered conditions, but it has an ability to survive on a wide range of environments.

Hazels were one of the first plants to race north as the glaciers retreated in Europe after the last Ice Age. Now they are commonly found on the acid soils of the Turkish mountains and Scotland’s wild, west coast, and are one of the few plants capable of growing on the windswept pure limestone of the Burren in Ireland.

Hazels are adapted to cool winters, wet springs, and warm summers. They are wind- pollinated during winter but fertilisation does not take place until spring, when the leaves are out and growing conditions are ideal.

Most of the growth on the hazel (both vegetative and reproductive) takes place over four to five months in spring and early summer at the same time that it is fattening its nut crop. In late summer, it drops its crop and quietly closes down for the winter.

Most of the world’s hazel production comes from Turkey, Italy and Spain and we have come to associate hazel growing with hot Mediterranean conditions.

However, the main hazel growing areas in these countries are not on the hot coasts but in cooler moister areas in the mountains. In Turkey, hazel growing is concentrated on the moister areas along the Black Sea, not on the Mediterranean coast, where almonds and walnuts dominate.


Hazels were introduced into New Zealand with the early settlers along with all the other food crops they were familiar with. Some of the early station orchards in Otago and Canterbury contained as many hazel trees as apples or pears.

When the NZ Tree Crops Association (NZTCA) formed in 1974, the hazelnut was one of first crops it promoted as having commercial possibilities. The NZTCA worked with the DSIR to import material and set up trials.

Collections of seedling hazel material were made by NZTCA members during the 1970s and 1980s. Assessment of this material led to the discovery of Whiteheart, now the main commercial hazel cultivar planted in New Zealand.


Hazel growing is dominated by small plantings on lifestyle blocks in the North Island, where the relatively low labour requirements have proven to be appealing. These growers are selling at small local markets.

The industry has moved to a more commercial scale in the south where hazels are thriving thanks to the work of local growers in the 1990s, who saw that lots of small growers competing for local markets would not move nut crops to an economically significant level.

The hazel industry in the South Island has significant plantings in Canterbury, Otago and Southland, but the challenge is to expand the research to match the needs of a larger industry nationwide.


The growing hazel industry needs to continue to expand research into problems limiting crop production and orchard profitability.

Even in the South Island, hazel growers have exited the industry, disillusioned with yields and returns that have failed to reach expectations

The majority of all new plantings are made up of a single cultivar, Whiteheart, plus its pollinators but there have been difficulties in getting Whiteheart to consistently deliver high yields in orchard situations.

It is grown because it has a high quality kernel that blanches well, but the question for new growers is, will it crop at levels that give a profitable return compared with other land uses?

Dr David McNeil’s work at Lincoln University indicated that Whiteheart had the flower numbers and yield efficiency to crop as well as overseas varieties. Murray’s work showed plantings he observed in new orchards had plenty of flower buds on 3-year-old plants so the yield problem probably lies with orchard management and yield limitations imposed by climate or pests and diseases.

Work funded by the HGANZ shows that the big bud mite does have an effect on yield, and Murray’s observations of the effect of the hazel leaf miner suggest that it probably also limits yields. The leaf minor is an insect pest that is well established throughout NZ but its economic significance was only recently discovered when it appeared in my own plantings, two years ago.


If we consider the areas of New Zealand with suitable soils and climate for hazel production, then hazelnuts could develop in to one of this country’s major horticultural crops.

The best sites lie mainly outside existing horticultural areas. If the site is suited to grapes, then it is probably too dry to be ideal for hazels. The main kiwifruit and avocado areas are too warm. This means hazel growing will be moving on to land dominated by cropping or livestock farming, and Murray is now running workshops encouraging farmers to plant hazels in riparian corridors, a win-win situation: a nut crop, and a tree that loves to suck up excess nitrogen before it enters waterways.

Hazel production certainly appears to fit the seasonal patterns of much of the irrigated land in the South Island better than dairying. The main requirements for irrigation water in hazel orchards are in spring and early summer, when snow-fed rivers are usually well supplied. Large amounts of water are not needed in the autumn or winter.

Hazels may also have potential in the central North Island where there are environmental concerns over the effect of dairying on nitrogen levels in the waterways. Murray’s research in 2012 backed this up but also provided the challenges growers would need to work on:


Hazelnuts are high in protein and require nitrogen to carry heavy crops, but this is mainly applied in spring when growth is active. Applications can be manipulated to avoid excess fertiliser use.


Murray has the following advice:

Is your land suited to mechanical harvesting?
Do you have adequate shelter? New shelter should be planted at least two years before the hazels are planted.
Do you need irrigation? If you have dry summers the answer will be yes. Contact local experts for advice.
Join the NZ Tree Crops Association and the Hazelnut Growers Association of NZ. This will give you access to the most recent information and contact with local growers. Field days at local orchards are a great way to learn about the crop.
Find the varieties suited for your area.
Do you plan to sell the crop yourself? If not, where are your markets?
Check your soil. Get a soil test and discuss fertility and drainage requirements with local horticultural experts.
Organise your tree requirements at least a year ahead of planting.


Each hazel variety has specific pollinators. At least 10% of your planting should be pollinators, either in pollinator rows, or spread through the planting.

Pollen release can vary from season to season so more than one pollinating variety is needed.

The pollinators below are listed from the earliest to the latest. In warmer climates growers should have mainly late pollinators.


Barcelona – Lansing, Daviana, Merveille de Bollwiller

Butler – Merveille de Bollwiller, Alexandra, Keen’s Late

Campanica – Butler, Lansing

Ennis – Merveille de Bollwiller, Alexandra, Keen’s Late

Lansing – Tonda di Giffoni, Whiteheart, Merveille de Bollwiller

Tonda di Giffoni – Barcelona, Lansing, Daviana

Tonda Romano – Barcelona, Merveille de Bollwiller

Whiteheart – Lansing, Merveille de Bollwiller, Alexandra, Keen’s Late


About the author

This article was written by hazelnut grower, NZ Tree Crops Association hazel research co-ordinator, and current chairman of the Hazelnut Growers Association Murray Redpath. Murray has spent the past 30+ years researching the hazelnut and running trials on his farm at Opotiki in the Bay of Plenty.



For more information

Hazelnut Growers Association


Hazelnut Growers Association guide


NZ Tree Crops Association – hazelnut guide


Hazelnut Nurseries



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The Health benefits of nuts

Packed with protein, fibre and essential fats, nuts are one of this season's best buys. A golf ball-sized portion (about 30g) of unsalted nuts makes a vitality-boosting snack and, unlike most other options, contributes a mix of valuable vitamins and minerals. All nuts have different nutrition credentials and will offer various health benefits - find your perfect match with our guide...

HFG guide to nuts

Eaten as a snack, sprinkled over salads or baked in treats, nutritionist Lisa Yates explains which nuts are best for you.

Get cracking

A new range of cold-pressed nut and seed oils produced by a group of Marlborough people will soon be available on supermarket shelves around the country.

The new joint venture between seed grower Garth Neal and Marlborough walnut and hazelnut producers Jenny and Malcolm Horwell was a collaboration of expertise, specialist equipment and hard work.