Macadamias: Palmitoleic Acid and Metabolic Health


Macadamias carry an unusual fat called palmitoleic acid. Most foods contain only traces of it, but in the USDA record for raw macadamias it makes up about 13 g of every 100 g of nut — more than twice the amount of palmitic acid, the saturated fat it is made from. Palmitoleic acid has a lively research story: mouse studies led scientists to call it a “lipokine”, a fat that behaves like a hormone, and several human studies link higher blood levels with better insulin sensitivity. Other human studies link the same blood marker with fatty liver and with the liver making new fat from sugar. A feeding trial found that, for LDL cholesterol, it behaved like a saturated fat rather than an unsaturated one. And the trials in which people actually ate macadamias did not show changes in blood sugar, insulin or weight. This page sets out each strand of evidence, labels what was done in animals, and keeps one distinction in view throughout: a blood level of palmitoleic acid is not the same thing as eating it.


Table of Contents

  1. What Palmitoleic Acid Is
  2. Where It Comes From: Macadamias, Sea Buckthorn and the Body Itself
  3. The “Lipokine” Idea From Animal Research
  4. A Blood Level Is Not the Same as Eating It
  5. Human Studies Linking It With Better Insulin Sensitivity
  6. Human Studies Linking It With Liver Fat-Making and Fatty Liver
  7. Cis and Trans: The Dairy Molecule Is a Different One
  8. The Feeding Trial: Palmitoleic Acid and LDL Cholesterol
  9. The Pure Palmitoleic Acid Trial: A Protocol, Not a Result
  10. What the Macadamia Trials Found for Glucose, Insulin and Weight
  11. Animal and Cell Studies of Macadamia Oil
  12. What Is Not Known
  13. Who the Research Raises Questions For
  14. Connections
  15. Key Research Papers
  16. Featured Videos

What Palmitoleic Acid Is

Fats are built from fatty acids — chains of carbon atoms. Palmitoleic acid has a chain of 16 carbons with one double bond, which makes it a monounsaturated fat, the same family as the oleic acid of olive oil. Chemists write it as 16:1 n-7: 16 carbons, 1 double bond, and that double bond sitting 7 carbons from the tail end of the chain. Because of that position it is sometimes marketed as an “omega-7” fat, by analogy with the omega-3 and omega-6 fats. Unlike those two families, omega-7 fats are not essential: the body can make all it needs.

The body makes palmitoleic acid from palmitic acid (16:0), the most common saturated fat in the human body and diet. An enzyme called stearoyl-CoA desaturase-1 (SCD1) inserts the double bond. Palmitoleic acid is one of the more abundant fatty acids in blood and tissues, particularly fat tissue and the liver (Frigolet 2017).

There are two shapes of the molecule. The form the body makes, and the form in macadamias, is cis-palmitoleic acid. A trans form also exists; it comes mainly from the fat of cattle, sheep and goats and from dairy products (Frigolet 2017). The two forms behave differently in research, and that difference matters later on this page.

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Where It Comes From: Macadamias, Sea Buckthorn and the Body Itself

Very few foods contain much palmitoleic acid. The two plant sources that appear again and again in the research are the macadamia nut and the oil of the sea buckthorn berry. A study of sea buckthorn fruit oil describes it as “rich in palmitoleic acid” (Gao 2017), and an Irish analysis of five nut oils found “substantial levels” of palmitoleic acid in macadamia, unlike walnuts, almonds, peanuts and hazelnuts, where oleic acid was the main monounsaturated fat (Maguire 2004). A 1994 trial team in Australia described macadamia oil as “at least one potentially large source” of it (Nestel 1994).

The USDA FoodData Central record for raw macadamia nuts (FDC 170178) gives these fat figures per 100 g:

Fatty acidPer 100 gPer 1 oz (28 g)
Total fat75.8 g21.2 g
All monounsaturated fat58.9 g16.5 g
Oleic acid (18:1)43.8 g12.3 g
Palmitoleic acid (16:1)13.0 g3.6 g
Palmitic acid (16:0, saturated)6.0 g1.7 g

The 1 oz column is the 100 g value multiplied by 0.28. So a 28 g handful carries roughly 3.6 g of palmitoleic acid — and, unusually, about twice as much of the unsaturated 16-carbon fat as of the saturated one. In most foods and in the human body the balance runs the other way.

The third source is the body itself. Because SCD1 turns palmitic acid into palmitoleic acid, a person who eats almost none still has it in the blood. As the following sections show, how much the body makes depends on its metabolic state, which is the root of most of the confusion about this fat.

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The “Lipokine” Idea From Animal Research

The interest in palmitoleic acid comes mainly from laboratory work. Experiments in mice showed that fat tissue releases palmitoleic acid into the blood and that it then acts on distant organs such as the liver and muscle. On that basis researchers proposed calling it a lipokine — a “lipid hormone”, a fat that carries signals between organs the way a hormone does (Frigolet 2017; Tricò 2020).

A 2017 review summarised the laboratory picture: in cell-culture experiments, the cis form influenced the survival of insulin-making beta cells in the pancreas, insulin release, muscle response to insulin and the behaviour of fat cells; and in animal studies, feeding cis-palmitoleic acid, or sources of it such as macadamia oil, partly prevented the metabolic damage caused by high-fat or high-sugar diets (Nunes 2017). The authors of the pure-palmitoleic-acid trial protocol describe the same preclinical findings — improved glucose tolerance, blood fats and fat build-up in muscle and liver in animal models (Cetin 2023).

These are findings in mice, rats and cells. The lipokine idea is a hypothesis about how human metabolism might work; it has not been shown in a controlled human trial that eating or taking palmitoleic acid produces these effects.

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A Blood Level Is Not the Same as Eating It

Almost all of the human evidence on palmitoleic acid and insulin comes from measuring it in blood, not from giving it to people. That distinction is the key to reading this research.

So when a study reports that people with more palmitoleic acid in their blood have better (or worse) insulin sensitivity, it is describing a marker that sits at the crossroads of diet, liver fat production and fat tissue release. It is not a test of what happens when someone eats macadamias.

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Human Studies Linking It With Better Insulin Sensitivity

Insulin sensitivity means how readily the body's tissues respond to insulin and take up sugar from the blood. Its opposite, insulin resistance, is a central feature of prediabetes and type 2 diabetes.

The European RISC cohort (2020)

The largest study in this area measured free fatty acids in the blood of 1,234 non-diabetic adults from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study, and again in 924 of them three years later. Insulin sensitivity was measured with a hyperinsulinaemic-euglycaemic clamp, the reference method, in which insulin is infused and researchers measure how much sugar must be given to keep blood sugar steady. After adjusting for age, sex, BMI, body fat and other fatty acids, higher blood palmitoleic acid went with better whole-body insulin sensitivity, lower liver insulin resistance, slightly better beta-cell function and lower blood sugar two hours after a glucose drink. People with high palmitoleic acid did not show the drop in insulin sensitivity that otherwise came with high palmitic acid. Over three years, a rise in palmitoleic acid went with a small rise in insulin sensitivity. The authors read this as support for palmitoleic acid as a beneficial lipokine released by fat tissue (Tricò 2020).

The associations were real but modest — standardised coefficients of 0.07 to 0.24 — and the study is observational: it shows the two travel together, not that one causes the other.

Type 1 diabetes versus controls (2013)

A US study of 25 people with type 1 diabetes and 25 without, all measured with a three-stage insulin clamp, found that free (unattached) palmitoleic acid in plasma went with better insulin sensitivity in the people without diabetes, but not in the people with type 1 diabetes. In the same study, palmitoleic acid held inside plasma triglycerides went the other way: higher levels went with worse insulin sensitivity of fat tissue (Bergman 2013). Even in one small study, then, the direction depended on which blood fraction was measured.

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Human Studies Linking It With Liver Fat-Making and Fatty Liver

The liver can turn surplus carbohydrate into new fat, a process called de novo lipogenesis (“fat-making from scratch”). Its first product is palmitic acid, and SCD1 then turns some of that into palmitoleic acid. When the liver is making a lot of fat, palmitoleic acid in the blood rises as a by-product. In non-alcoholic fatty liver disease this process is often running high.

The Dallas fat-making study (2015)

Researchers at the University of Texas Southwestern gave 24 overweight adults heavy water (deuterium-labelled water) to drink for 10 days, which lets new fat made by the liver be measured directly, and measured liver fat with magnetic resonance spectroscopy. Palmitoleic acid in VLDL triglycerides — the fat particles the liver sends out into the blood — correlated with measured liver fat-making (r = 0.56), with liver fat (r = 0.53) and with insulin resistance of fat tissue (r = 0.56). People with high liver fat (an average of 18.4%) had 45% more palmitoleic acid in these particles than people with low liver fat (3.1%), and their liver fat-making was 2.5 times higher. The authors proposed this palmitoleic acid level as a biomarker of elevated liver fat where isotope testing is not possible, while calling for larger confirming studies. They also noted that because so little palmitoleic acid comes from the diet, it is a cleaner signal of liver fat-making than palmitic acid, which the diet supplies in quantity (Lee 2015).

The reviews

A 2017 review of the whole field found mixed cardiovascular effects and correlations with obesity and fatty liver that run in both directions, while describing a more consistent link with protection from insulin resistance and diabetes (Frigolet 2017). A second 2017 review was more cautious about the form that matters for macadamias: it found the human data on blood cis-palmitoleic acid “still controversial” (Nunes 2017).

Putting the two sides together

Both sets of findings can be true at once. Palmitoleic acid released by healthy fat tissue may be a helpful signal, while palmitoleic acid pumped out by a fat-making liver is a sign of metabolic strain. A single blood number cannot tell which source dominates. That is why a high blood level appears on both sides of the ledger in the research, and why it says little on its own about the effect of eating a food that contains it.

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Cis and Trans: The Dairy Molecule Is a Different One

The cis and trans forms of palmitoleic acid have the same atoms but a different shape around the double bond. The body makes the cis form; the trans form (trans-16:1 n-7) comes mainly from ruminant fat and dairy foods, although the body makes a little too (Frigolet 2017).

This matters because a review of the human studies found that the positive associations with insulin sensitivity and with a lower onset of type 2 diabetes were seen mainly for trans-palmitoleic acid in plasma phospholipids, while the data on cis-palmitoleic acid were still controversial (Nunes 2017). Macadamias supply the cis form. Findings about trans-palmitoleic acid, which mostly reflect dairy fat intake, cannot be carried over to macadamias.

Trans-palmitoleic acid from dairy is also a different matter from the industrial trans fats once made by partially hydrogenating vegetable oils, which are covered on the trans fats page.

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The Feeding Trial: Palmitoleic Acid and LDL Cholesterol

One controlled feeding trial asked the direct question: does palmitoleic acid act on blood cholesterol like an unsaturated fat or like a saturated one? It was prompted by macadamia oil being a large potential source of it.

For scale: 4% of energy on a 2,000 kcal day works out to about 9 g of fat, roughly the palmitoleic acid in 70 g of macadamias by the USDA figure (this is arithmetic, not a dose given in the trial). The trial tested the isolated fatty acid, not the whole nut. The whole-nut trials, described on the heart health page, are a different test: when macadamias replaced foods higher in saturated fat, LDL fell compared with an average American diet (Griel 2008), and in 17 men with high cholesterol LDL fell 5.3% and HDL rose 7.9% over 4 weeks, in a before-and-after design (Garg 2003). The nut brings far more oleic acid than palmitoleic acid, and it displaces other fats from the diet, so the two kinds of trial do not contradict each other — but the 1994 result is a reason the cholesterol benefit of macadamias is not usually credited to palmitoleic acid.

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The Pure Palmitoleic Acid Trial: A Protocol, Not a Result

Because observational studies cannot settle cause and effect, a research group at Brigham and Women's Hospital and Harvard Medical School published the design of a randomised, double-blind, placebo-controlled trial. It is designed to test whether purified palmitoleic acid increases insulin sensitivity and reduces liver fat-making in overweight and obese adults with prediabetes (Cetin 2023).

Until results from a trial like this are published, there is no controlled human evidence that taking palmitoleic acid improves insulin sensitivity.

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What the Macadamia Trials Found for Glucose, Insulin and Weight

If palmitoleic acid from food improved blood-sugar control, the trials in which people ate macadamias would be the place to see it. The trials in the research record for this page did not find that.

Free-living adults with abdominal obesity (2023)

In a randomised crossover trial at Loma Linda University, 35 adults with abdominal obesity and raised cardiometabolic risk ate their usual diet plus macadamias, supplying about 15% of daily calories, for 8 weeks, and their usual diet without nuts for 8 weeks, with a 2-week washout between. Total fat and monounsaturated fat intake rose, while saturated fat intake did not change. There were no significant changes in glycaemic (blood-sugar) measures, and no significant changes in weight, BMI, waist size or body fat. Total and LDL cholesterol fell by 2.1% and 4%, but these drops were not statistically significant (Jones 2023). The trial does show that adding this calorie-dense nut for 8 weeks did not lead to weight or fat gain in these adults.

Men with high cholesterol (2003)

The Australian trial in 17 men eating 40–90 g a day for 4 weeks raised blood palmitoleic acid and improved the lipid profile; its abstract reports no blood-sugar or insulin outcome (Garg 2003).

A single macadamia-oil meal (2014)

A Danish study gave a meal with 72% of its energy from monounsaturated fat, as macadamia nut oil, to 17 first-degree relatives of people with type 2 diabetes and 17 people without that family history. Blood fats, insulin, glucose and gut hormones over the next four hours did not differ between the two groups; gene activity in muscle and fat tissue did differ in a pattern the authors read as early defects in fat handling in the relatives (Pietraszek 2014). The study compared two groups of people, not macadamia oil against another fat, so it does not show whether the oil helped or harmed glucose control.

A small snack study (2024)

In a Chinese crossover study of 17 healthy young women monitored with continuous glucose sensors, 70 kcal snacks of chicken breast, apple or macadamia were compared with no snack. A macadamia snack eaten mid-morning was followed by higher insulin resistance after lunch than no snack; eaten just before lunch it made no difference. The chicken snack steadied glucose and lowered insulin resistance; the macadamia snack did not, at either time (Lou 2024). This was a small, short study of one-off snacks in healthy people.

What these trials add up to

None of the macadamia trials here showed an improvement in blood sugar, insulin or insulin sensitivity. The 2023 trial found no change in glycaemic measures over 8 weeks; the 2024 snack study found no benefit and one unfavourable comparison. The cholesterol findings are covered in the sibling article on heart health and monounsaturated fats.

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Animal and Cell Studies of Macadamia Oil

The more striking metabolic results come from animals. All of the studies below were done in mice, rats or cells.

These studies used oil, not whole nuts, often at doses scaled to body weight that are far above what people eat. They suggest possible mechanisms; they are not evidence of an effect in people.

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What Is Not Known

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Who the Research Raises Questions For

Questions about blood sugar, fatty liver or cholesterol treatment belong with a clinician, who can interpret tests such as fasting insulin, HOMA-IR and a lipid panel in context.

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Connections

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Key Research Papers

  1. Nestel P, Clifton P, Noakes M. Effects of increasing dietary palmitoleic acid compared with palmitic and oleic acids on plasma lipids of hypercholesterolemic men. Journal of lipid research. 1994;35(4):656-62. PubMed PMID: 8006520
  2. Tricò D, Mengozzi A, Nesti L, et al. Circulating palmitoleic acid is an independent determinant of insulin sensitivity, beta cell function and glucose tolerance in non-diabetic individuals: a longitudinal analysis. Diabetologia. 2020;63(1):206-218. PubMed PMID: 31676981
  3. Lee JJ, Lambert JE, Hovhannisyan Y, et al. Palmitoleic acid is elevated in fatty liver disease and reflects hepatic lipogenesis. The American journal of clinical nutrition. 2015;101(1):34-43. PubMed PMID: 25527748
  4. Bergman BC, Howard D, Schauer IE, et al. The importance of palmitoleic acid to adipocyte insulin resistance and whole-body insulin sensitivity in type 1 diabetes. The Journal of clinical endocrinology and metabolism. 2013;98(1):E40-50. PubMed PMID: 23150678
  5. Cetin E, Pedersen B, Porter LM, et al. Protocol for a randomized placebo-controlled clinical trial using pure palmitoleic acid to ameliorate insulin resistance and lipogenesis in overweight and obese subjects with prediabetes. Frontiers in endocrinology. 2023;14:1306528. PubMed PMID: 38313838
  6. Frigolet ME, Gutiérrez-Aguilar R. The Role of the Novel Lipokine Palmitoleic Acid in Health and Disease. Advances in nutrition (Bethesda, Md.). 2017;8(1):173S-181S. PubMed PMID: 28096141
  7. Nunes EA, Rafacho A. Implications of Palmitoleic Acid (Palmitoleate) On Glucose Homeostasis, Insulin Resistance and Diabetes. Current drug targets. 2017;18(6):619-628. PubMed PMID: 26648072
  8. Jones JL, Sabaté J, Heskey C, et al. Macadamia nut effects on cardiometabolic risk factors: a randomised trial. Journal of nutritional science. 2023;12:e55. PubMed PMID: 37180485
  9. Garg ML, Blake RJ, Wills RB. Macadamia nut consumption lowers plasma total and LDL cholesterol levels in hypercholesterolemic men. The Journal of nutrition. 2003;133(4):1060-3. PubMed PMID: 12672919
  10. Griel AE, Cao Y, Bagshaw DD, et al. A macadamia nut-rich diet reduces total and LDL-cholesterol in mildly hypercholesterolemic men and women. The Journal of nutrition. 2008;138(4):761-7. PubMed PMID: 18356332
  11. Pietraszek A, Gregersen S, Pedersen SB, et al. Acute effects of monounsaturated fat on postprandial lipemia and gene expression in first-degree relatives of subjects with type 2 diabetes. European journal of clinical nutrition. 2014;68(9):1022-8. PubMed PMID: 24824014
  12. Lou X, Fan Z, Wei J, et al. Timing and Nutrient Type of Isocaloric Snacks Impacted Postprandial Glycemic and Insulinemic Responses of the Subsequent Meal in Healthy Subjects. Nutrients. 2024;16(4):535. PubMed PMID: 38398859
  13. Maguire LS, O'Sullivan SM, Galvin K, et al. Fatty acid profile, tocopherol, squalene and phytosterol content of walnuts, almonds, peanuts, hazelnuts and the macadamia nut. International journal of food sciences and nutrition. 2004;55(3):171-8. PubMed PMID: 15223592
  14. Chowdhury R, Warnakula S, Kunutsor S, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Annals of internal medicine. 2014;160(6):398-406. PubMed PMID: 24723079
  15. Lima EA, Silveira LS, Masi LN, et al. Macadamia oil supplementation attenuates inflammation and adipocyte hypertrophy in obese mice. Mediators of inflammation. 2014;2014:870634. PubMed PMID: 25332517
  16. Barrena HC, Schiavon FP, Cararra MA, et al. Effect of linseed oil and macadamia oil on metabolic changes induced by high-fat diet in mice. Cell biochemistry and function. 2014;32(4):333-40. PubMed PMID: 24284975
  17. Shuai X, Dai T, McClements DJ, et al. Hypolipidemic effects of macadamia oil are related to AMPK activation and oxidative stress relief: In vitro and in vivo studies. Food research international (Ottawa, Ont.). 2023;168:112772. PubMed PMID: 37120222
  18. Zhang M, Zhang Y, Li L, et al. Macadamia (Macadamia integrifolia) Oil Prevents High-Fat Diet-Induced Lipid Accumulation and Oxidative Stress by Activating the AMPK/Nrf2 Pathway. Foods (Basel, Switzerland). 2024;13(22):3672. PubMed PMID: 39594087
  19. Gao S, Guo Q, Qin C, et al. Sea Buckthorn Fruit Oil Extract Alleviates Insulin Resistance through the PI3K/Akt Signaling Pathway in Type 2 Diabetes Mellitus Cells and Rats. Journal of agricultural and food chemistry. 2017;65(7):1328-1336. PubMed PMID: 28134520

PubMed Topic Searches

  1. Palmitoleic acid and insulin sensitivity
  2. Palmitoleic acid, de novo lipogenesis and fatty liver
  3. Trans-palmitoleic acid and diabetes
  4. Macadamia randomised controlled trials
  5. Palmitoleic acid as a lipokine
  6. Sea buckthorn and palmitoleic acid

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