Macadamias — Benefits Deep Dive

Almost everything researchers have studied about macadamias comes back to one unusual fat profile. By the USDA figures, about 78% of the nut’s fat is monounsaturated, about 17% of it is a rare fat called palmitoleic acid, and only about 2% is polyunsaturated — far less omega-6 than any other common nut. The heart-health trials, the metabolic research and the food-chemistry work on why macadamia oil keeps so well are three different readings of that same fat.

The three articles below take each in turn. They also share one caveat: the human evidence on macadamias themselves is small. A handful of feeding trials, the largest with 35 people and the longest lasting 8 weeks, measured blood markers rather than heart attacks or deaths, and much of the striking metabolic and antioxidant work was done in mice or cells.

Deep-Dive Articles

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Heart Health and Monounsaturated Fats

Every macadamia feeding trial one by one, the nut meta-analyses, the research on swapping saturated for monounsaturated fat, and the FDA’s 2017 qualified health claim. LDL fell when macadamias replaced foods higher in saturated fat, but the trials are few, small and short, and none counted heart attacks or deaths.

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Palmitoleic Acid and Metabolic Health

The omega-7 fat that mouse studies cast as a “lipokine”, and the human blood-level studies that link it both with better insulin sensitivity and with fatty liver. A 1994 feeding trial found it acted like a saturated fat on LDL, and the macadamia trials showed no improvement in blood sugar or insulin.

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Oil, Tocotrienols and Oxidative Stability

Why macadamia fat is so slow to go rancid, what has actually been measured of its vitamin E forms, squalene and plant sterols, and what roasting temperature does to kernel quality. It keeps stability in the jar separate from any effect in the body, where the evidence so far comes from mice and cells.

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Why One Fat Profile Explains Macadamia Research

Fats in food are built from fatty acids, and what matters most is how many double bonds each chain carries. Saturated fats have none, monounsaturated fats have one, and polyunsaturated fats have two or more. Per 100 g of raw macadamias, the USDA lists 75.8 g of fat: 58.9 g monounsaturated (about 78%), 12.1 g saturated (about 16%) and only 1.5 g polyunsaturated (about 2%). The monounsaturated part is split roughly three to one between oleic acid, the main fat of olive oil, and palmitoleic acid, which most foods carry only in traces. Each of the three deep dives follows one consequence of that profile.

The heart question follows the monounsaturated share. Feeding trials consistently find that replacing saturated fat with unsaturated fat lowers LDL cholesterol, and macadamias are one of the richest whole-food sources of monounsaturated fat. In the macadamia trials, though, the comparison decided the result. LDL fell when macadamias replaced a diet higher in saturated fat — in the best-designed trial, 42.5 g per 2,100 kcal for 5 weeks gave an LDL of 3.14 versus 3.44 mmol/L on an average American diet. It came out the same as a low-fat or Step-1 diet. When macadamias were simply added to the usual diet in the 2023 trial of 35 adults, LDL fell 4%, a change that was not statistically significant. Across the trials with reported sizes, roughly 125 people have been studied for 4 to 8 weeks each, and no trial counted heart attacks, strokes or deaths. The large nut meta-analyses give no sign that macadamias lower LDL more than other nuts despite their higher monounsaturated fat.

The FDA claim carries its own conditions. In 2017 the US Food and Drug Administration said it would allow a qualified health claim, after a petition filed on behalf of a macadamia producer. It drew conclusions from three small studies totalling 72 participants and found “consistent but limited scientific evidence” when macadamias are substituted for other sources of saturated fat. As reported on the heart page, the permitted wording is: “Supportive but not conclusive research shows that eating 1.5 ounces per day of macadamia nuts, as part of a diet low in saturated fat and cholesterol and not resulting in increased intake of saturated fat or calories may reduce the risk of coronary heart disease. See nutrition information for fat [and calorie] content.” “Qualified” means the evidence falls short of the significant scientific agreement a full claim needs.

The saturated fat is the other side of the same profile. At about 12 g per 100 g, macadamias carry two to three times the saturated fat of hazelnuts or almonds. Raw macadamias have 6.03 g of saturated fat per 50 g, above the 4 g level that ordinarily disqualifies a food from a heart-health claim. The FDA allowed the claim anyway on condition that the label carries a saturated-fat disclosure directly beneath it.

The metabolic question follows the palmitoleic acid. Macadamias supply about 13 g of palmitoleic acid per 100 g, roughly 3.6 g in a 28 g handful. Mouse studies led researchers to call it a “lipokine”, a fat that carries signals between organs like a hormone, and some large human cohorts link higher blood levels with better insulin sensitivity. But most of that research is not about macadamias. The body makes most of its own palmitoleic acid, so a blood level mostly reflects the liver and fat tissue rather than diet, and other human studies link the same blood marker with liver fat-making and fatty liver. The review evidence on the cis form found in macadamias is described as “still controversial”, and the only trial of pure palmitoleic acid in the records was published as a protocol with no results. In the trials where people actually ate macadamias, blood sugar, insulin and weight did not improve; a small snack study found one unfavourable comparison.

Palmitoleic acid also complicates the cholesterol story. Although it is chemically monounsaturated, a 1994 feeding trial in 34 men with high cholesterol found that LDL on a palmitoleic-enriched diet was similar to LDL on a palmitic (saturated) diet, and both were significantly higher than on an oleic diet; the authors concluded that it “behaves like a saturated and not a monounsaturated fatty acid in its effect on LDL cholesterol.” That trial used concentrated fatty acids, not whole nuts, and has not been repeated in the records gathered here. It is one reason the cholesterol results of macadamias are usually credited to their oleic acid and to the saturated fat they displace.

The stability question follows the missing omega-6. Oxygen attacks fats most easily where a chain has two or more double bonds, so a fat with very little polyunsaturated content resists going rancid. That is why macadamia kernels and oil keep well compared with walnuts or seed oils. The same fact means macadamias supply almost none of the essential omega-6 and omega-3 fats. The deep dive keeps stability in the jar separate from any effect in the body: no human macadamia trial reviewed reported an oxidative-stress or inflammation marker, the positive findings on antioxidant enzymes come from mice and liver cells, and one independent mouse study found macadamia oil no better than soybean oil. The USDA lists only 0.54 mg of vitamin E (alpha-tocopherol) per 100 g, and no tocotrienol figure for macadamias could be confirmed.

Taken together, the three pages describe one food whose fat is genuinely unusual, measured in a small number of short human trials, with much of the wider story borrowed from research on monounsaturated fat in general, on palmitoleic acid as a blood marker, and on macadamia oil in animals. Each deep dive sets out what that evidence does and does not show, including the null results.

Research Papers: Heart Health and Monounsaturated Fats

  1. 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
  2. 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
  3. 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
  4. 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
  5. Nishi SK, Paz-Graniel I, Ni J, et al. Effect of nut consumption on blood lipids: An updated systematic review and meta-analysis of randomized controlled trials. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2025;35(5):103771. PubMed PMID: 39638677
  6. Gardner CD, Kraemer HC. Monounsaturated versus polyunsaturated dietary fat and serum lipids. A meta-analysis. Arteriosclerosis, thrombosis, and vascular biology. 1995;15(11):1917-27. PubMed PMID: 7583572
  7. Hooper L, Martin N, Jimoh OF, et al. Reduction in saturated fat intake for cardiovascular disease. The Cochrane database of systematic reviews. 2020;8(8):CD011737. PubMed PMID: 32827219
  8. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. The New England journal of medicine. 2018;378(25):e34. PubMed PMID: 29897866

Research Papers: Palmitoleic Acid and Metabolic Health

  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. 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
  5. 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
  6. 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
  7. 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
  8. 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

Research Papers: Oil, Tocotrienols and Oxidative Stability

  1. 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
  2. Maestri D. Groundnut and tree nuts: a comprehensive review on their lipid components, phytochemicals, and nutraceutical properties. Critical reviews in food science and nutrition. 2024;64(21):7426-7450. PubMed PMID: 39093582
  3. Aruwajoye NN, Buthelezi NMD, Mditshwa A, et al. Assessing the Impact of Roasting Temperatures on Biochemical and Sensory Quality of Macadamia Nuts (Macadamia integrifolia). Foods (Basel, Switzerland). 2023;12(11). PubMed PMID: 37297359
  4. 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
  5. 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). PubMed PMID: 39594087
  6. 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
  7. 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
  8. Hansen SR, Buck WB, Meerdink G, et al. Weakness, tremors, and depression associated with macadamia nuts in dogs. Veterinary and human toxicology. 2000;42(1):18-21. PubMed PMID: 10670081

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