Macadamias: Heart Health and Monounsaturated Fats

Table of Contents

1. What a Monounsaturated Fat Is
2. The Macadamia Fat Profile Beside Olive Oil and Other Nuts
3. The Macadamia Feeding Trials, One by One
4. Reading the Trials Together
5. The Palmitoleic Acid Question
6. Oxidative Stress and Inflammation Markers
7. Blood Vessels and the Hours After a Meal
8. Where Macadamias Sit in the Nut Meta-Analyses
9. Replacing Saturated Fat With Monounsaturated Fat
10. Heart Attacks, Strokes and Deaths: The Indirect Evidence
11. The FDA Qualified Health Claim (2017)
12. What Is Not Known
13. Who the Research Raises Concerns For
14. Connections
15. Key Research Papers
16. Featured Videos

What a Monounsaturated Fat Is

Every fat in food is built mostly from fatty acids — chains of carbon atoms with hydrogen attached. The chemistry that matters for health is how many double bonds the chain contains:

• Saturated fatty acids have no double bonds. The chain is straight, so these fats pack tightly and tend to be solid at room temperature (butter, coconut oil, the fat in meat). Palmitic acid (16 carbons) and stearic acid (18 carbons) are the common ones.
• Monounsaturated fatty acids (MUFA) have exactly one double bond, which puts a kink in the chain. These fats are liquid at room temperature but can thicken in the fridge — olive oil is the familiar example.
• Polyunsaturated fatty acids (PUFA) have two or more double bonds. They include the essential omega-6 linoleic acid and omega-3 alpha-linolenic acid, which the body cannot make. Each double bond is a spot where oxygen can attack, which is why oils rich in PUFA go rancid faster.

Oleic acid: the main monounsaturated fat

Oleic acid has 18 carbons and its one double bond at the ninth carbon from the tail end, so nutrition writers call it an omega-9 fat (written 18:1 n-9). It is the dominant fat of olive oil, avocado, almonds, hazelnuts and macadamias, and the human body can also make it. The FDA's 2017 review of macadamias names oleic acid as their principal fatty acid (FDA letter, 2017).

Palmitoleic acid: the unusual one

Palmitoleic acid has 16 carbons and its double bond at the seventh carbon from the tail, making it an omega-7 fat (16:1 n-7). Most foods carry only traces of it. The body makes its own palmitoleic acid from palmitic acid, mainly in the liver and fat tissue. Macadamias are one of the few foods that supply it in quantity: an analysis of five nut oils found oleic acid to be the main monounsaturated fat in all of them, with "substantial levels" of palmitoleic acid present only in the macadamia (Maguire 2004). Although it is chemically a monounsaturated fat, one feeding trial found it did not behave like oleic acid on LDL cholesterol — that trial is described below, and the wider metabolic research has its own article, Macadamias: Palmitoleic Acid and Metabolic Health.

Why the type of fat matters for cholesterol

LDL cholesterol is carried in the blood by particles that the liver clears through receptors on its surface. Diets high in saturated fat are consistently found in feeding trials to raise LDL, and swapping that saturated fat for unsaturated fat lowers it (see Replacing Saturated Fat). Most of the cholesterol effect of any high-fat food therefore depends on what it replaces in the diet. That point turns out to be central to every macadamia trial and to the FDA's reading of them.

The Macadamia Fat Profile Beside Olive Oil and Other Nuts

The figures below come from USDA FoodData Central, per 100 g of each food: raw macadamias (FDC 170178), olive oil (FDC 171413), raw avocado (FDC 171705), hazelnuts (FDC 170581) and almonds (FDC 170567). The percentage column is each fat type as a share of the food's total fat, calculated from those records.

Four features stand out:

• Monounsaturated share. At about 78% of its fat, the macadamia matches or slightly exceeds olive oil (73%) and hazelnuts (75%). The FDA's review gives the same picture: roughly 16% saturated, 78% monounsaturated and 2% polyunsaturated (FDA letter, 2017).
• Palmitoleic acid. Macadamias carry about 13 g of palmitoleic acid per 100 g — around 17% of their fat, ten times the amount in the same weight of olive oil. Olive oil's monounsaturated fat is almost all oleic acid; the macadamia's is split roughly three parts oleic to one part palmitoleic.
• Very little polyunsaturated fat. At 1.5 g per 100 g (1.3 g of it omega-6 linoleic acid), macadamias have far less polyunsaturated fat than olive oil, avocado or any other common nut. That makes the fat chemically stable — the subject of Macadamias: Oil, Tocotrienols and Oxidative Stability — but it also means macadamias supply almost none of the essential omega-3 or omega-6 fats.
• More saturated fat than other nuts. Macadamias contain about 12 g of saturated fat per 100 g, roughly half of it palmitic acid (6.0 g). That is two to three times the saturated fat of hazelnuts or almonds, and it is the reason macadamias exceed the FDA's ordinary saturated-fat limit for a heart-health claim (see the FDA section).

Because the macadamia is a whole food, its fat arrives with fibre (8.6 g per 100 g in the USDA record) and plant sterols (116 mg per 100 g, mostly beta-sitosterol). Phytosterols have a structure similar to cholesterol; the nut-oil analysis above found beta-sitosterol to be the most abundant sterol in every nut tested, alongside squalene and tocopherols (Maguire 2004). The full nutrient table is on Macadamias: Nutrient Profile.

The Macadamia Feeding Trials, One by One

The FDA's 2017 review found five intervention studies designed to test macadamias and heart-disease risk markers, and judged that conclusions could be drawn from three of them (FDA letter, 2017). A sixth trial, published in 2023, came after that review. They are listed in date order. Two of the older studies (Colquhoun 1996 and Curb 2000) are described here from the FDA's account of them, because their original papers are not in the PubMed records gathered for this article; their figures below are the FDA's.

1. Australia, 1996 (Colquhoun and colleagues) — 14 adults

• Who: 14 Australian adults whose cholesterol ranged from normal to high (total cholesterol 155–309 mg/dL; average LDL 160 mg/dL).
• Design: a 12-week, three-period study. Everyone first spent 4 weeks on their usual diet, which the FDA describes as representative of an average American diet (37% of energy from fat, 16% saturated, 14% monounsaturated). Participants were then randomised to two 4-week diets in turn.
• The diets: a macadamia diet in which the nuts supplied 20% of energy (42% fat, 11% saturated, 31% monounsaturated) and a low-fat, high-carbohydrate diet (21% fat, 9% saturated, 8% monounsaturated).
• Result: total and LDL cholesterol were significantly lower on the macadamia diet than on the usual diet. They did not differ between the macadamia diet and the low-fat diet.
• FDA rating: moderate methodological quality.

2. United States, 2000 (Curb and colleagues) — 34 adults

• Who: 34 US adults with normal to high cholesterol (total cholesterol 157–272 mg/dL; average LDL 134 mg/dL).
• Design: a randomised crossover controlled-feeding study with three 30-day diet periods. In a crossover study each person eats every diet in turn, so each serves as their own comparison.
• The diets: a macadamia diet (37% fat, 9% saturated, 21% monounsaturated), an average American diet (37% fat, 16% saturated, 14% monounsaturated) and the American Heart Association-style Step-1 diet (30% fat, 9% saturated, 14% monounsaturated). The macadamia dose was 34 g per 1,000 kcal, a mean of about 116 g a day, or roughly 31% of energy — a figure the FDA notes came from personal communication with the study author rather than from the paper.
• Result: compared with the average American diet, the macadamia diet lowered total cholesterol (P < 0.01) and LDL cholesterol (P < 0.05). It did not differ from the Step-1 diet.
• FDA rating: moderate methodological quality.

3. Australia, 2003 (Garg and colleagues) — 17 men

• Who: 17 men with high cholesterol, average age 54 (Garg 2003).
• Design: each man added 40–90 g of macadamias a day, equivalent to 15% of energy, for 4 weeks. Blood was measured before and after.
• Result: total cholesterol fell 3.0%, LDL cholesterol fell 5.3% and HDL cholesterol rose 7.9%. Triglycerides and homocysteine (an amino acid in blood that is studied as a cardiovascular marker) did not change. Blood levels of the monounsaturated fats 16:1 n-7 (palmitoleic acid), 18:1 n-7 and 20:1 n-9 rose, while omega-6 and omega-3 levels were unaffected. The men's diets shifted towards more monounsaturated fat and relatively less saturated fat and PUFA.
• The limitation: the FDA classed this as a single-arm study with no control group. Without one, it is not possible to tell whether the changes came from the nuts or from other things that changed over the same four weeks; the FDA therefore drew no conclusions from it.

4. 2004 (Hiraoka-Yamamoto and colleagues)

The FDA reviewed a 2004 study by Hiraoka-Yamamoto and colleagues and drew no conclusions from it, stating that it lacked an identifiable control group and did not report statistical comparisons between treatments (FDA letter, 2017). Its details are not reported here because the paper itself is not among the records gathered for this article.

5. United States, 2008 (Griel and colleagues) — 25 adults

• Who: 25 adults with mildly raised cholesterol, 15 women and 10 men (the FDA's review counts 24) (Griel 2008).
• Design: a randomised crossover controlled-feeding study — all food was supplied — with two 5-week diet periods.
• The diets: both were 33% fat. The macadamia diet included 42.5 g (1.5 oz) of nuts per 2,100 kcal and provided 7% of energy from saturated fat and 18% from monounsaturated fat. The comparison "average American diet" provided 13% saturated and 11% monounsaturated. So the total fat was the same; what changed was which fat.
• Result: after the macadamia diet, total cholesterol was 4.94 mmol/L versus 5.45 mmol/L, and LDL cholesterol 3.14 versus 3.44 mmol/L (both P < 0.05). Non-HDL cholesterol (3.83 vs 4.26), the total-to-HDL ratio (4.60 vs 4.89) and the LDL-to-HDL ratio (2.91 vs 3.09) were also lower. Triglycerides did not change.
• FDA rating: the only one of the three usable studies judged to be of high methodological quality. Its 42.5 g per 2,100 kcal is the lowest intake that produced a significant cholesterol reduction, and it is where the "1.5 ounces per day" in the FDA claim comes from.

6. United States, 2023 (Jones and colleagues) — 35 adults

• Who: 35 adults with abdominal obesity, at raised cardiometabolic risk (Jones 2023). This is the largest macadamia trial.
• Design: a randomised crossover trial in everyday ("free-living") conditions. Participants ate their usual diet plus macadamias, about 15% of daily calories, for 8 weeks, and their usual diet without nuts for 8 weeks, with a 2-week washout between.
• What changed in the diet: total fat and monounsaturated fat intake rose; saturated fat intake did not change. Unlike the 2008 trial, the nuts were added rather than swapped for saturated fat.
• Result: total cholesterol fell 2.1% (−4.3 mg/dL; 95% confidence interval −14.8 to 6.1) and LDL 4% (−4.7 mg/dL; −14.3 to 4.8). Neither change was statistically significant — both confidence intervals include zero. Weight, BMI, waist, body-fat percentage and blood-sugar measures did not change significantly. Cholesterol lowering was greater in participants with overweight than in those with obesity, and in those below the median body fat.
• The authors' reading: the non-significant cholesterol reduction was of similar size to that seen with other nuts, and it occurred without any change in saturated fat intake.

A related trial: mixed nuts including macadamias

A 16-week randomised trial in 29 adults with overweight or obesity compared 42.5 g a day of mixed nuts — cashews, almonds, macadamias, Brazil nuts, pecans, pistachios, walnuts and peanuts — with 69 g a day of pretzels supplying the same calories. Total, LDL and HDL cholesterol and lipoprotein(a) did not differ between the groups. The nut group had lower body-fat percentage and diastolic blood pressure and higher adiponectin, a hormone released by fat tissue that is linked with insulin sensitivity (Nora 2023). The authors declared no conflicts of interest. Because macadamias were one of eight nuts, this trial cannot isolate them.

Reading the Trials Together

Across the five macadamia studies with reported sizes, roughly 125 people have been tested on macadamia diets for between 4 and 8 weeks each. A few patterns emerge:

• The comparison decides the result. Every controlled trial that found a significant LDL reduction compared macadamias with a diet higher in saturated fat. When macadamias were compared with a low-fat or Step-1 diet that was also low in saturated fat, LDL came out the same. When macadamias were simply added on top of the usual diet without lowering saturated fat, the reduction was small and not statistically clear. The FDA drew the same conclusion: the evidence links macadamias with lower cholesterol "when macadamia nuts are substituted for other sources of saturated fat in the diet" (FDA letter, 2017).
• HDL and triglycerides barely moved. Only the uncontrolled 2003 study reported an HDL rise. No macadamia trial reported a change in triglycerides.
• The amounts were large. Doses ranged from about 42 g a day to more than 100 g a day — 15% to 31% of all calories. Those are much larger portions than a typical handful.
• Funding is not reported in the abstracts. None of the trial abstracts read for this article states its funding source. The FDA review itself was triggered by a petition submitted in 2015 on behalf of a macadamia producer.

The Palmitoleic Acid Question

Because macadamias are the richest food source of palmitoleic acid, Australian researchers tested whether that fat lowers LDL as oleic acid does. Their 1994 paper notes that macadamia oil is "at least one potentially large source of palmitoleic acid" (Nestel 1994).

• Who and how: 34 men with high cholesterol ate three test diets in random order, 3 weeks each. Supplements raised one of three fatty acids at a time: palmitic acid (saturated, +4% of energy), palmitoleic acid (+4% of energy) or oleic acid (+3% of energy). Dietary cholesterol was kept low (under 165 mg a day).
• Result: total and LDL cholesterol were similar on the palmitoleic and palmitic diets, and both were significantly higher than on the oleic diet. HDL cholesterol was significantly lower on palmitoleic than on palmitic acid.
• The authors' conclusion: palmitoleic acid "behaves like a saturated and not a monounsaturated fatty acid in its effect on LDL cholesterol."

This is one trial of a few dozen men, using concentrated fatty acids rather than whole nuts, and it has not been repeated in the records gathered here. But it matters for how macadamia fat is described. If palmitoleic acid acts on LDL more like palmitic acid than oleic acid, then the macadamia's effective "cholesterol-neutral" monounsaturated fat is closer to 44 g per 100 g (its oleic acid) than to the full 59 g. It may also help explain why the macadamia trials found LDL reductions of similar size to other nuts rather than larger ones. The broader metabolic research on palmitoleic acid — insulin sensitivity, fatty liver, its role as a "lipokine" — is in Palmitoleic Acid and Metabolic Health.

Oxidative Stress and Inflammation Markers

Oxidative stress is damage caused by reactive oxygen molecules; inflammation markers such as C-reactive protein (CRP) are proteins in the blood that rise when the immune system is activated. Both are studied because they are linked with the build-up of plaque in arteries. The human evidence for macadamias on these markers is very thin.

In people

• The 2003 Australian study measured homocysteine and found no change (Garg 2003). The abstracts of the 2008 and 2023 macadamia trials do not report oxidative-stress or inflammation outcomes (Griel 2008; Jones 2023).
• In the 16-week mixed-nut trial, CRP and 8-oxo-deoxyguanosine (8-oxodG, a marker of oxidative damage to DNA) showed downward trends, and total antioxidant capacity an upward trend, in the nut group — but none of these changes was statistically significant (Nora 2023).
• A trial in 75 people with metabolic syndrome compared four 12-week diets: high in saturated fat, high in monounsaturated fat, and two low-fat diets. After a test meal matching each diet, blood levels of bacterial endotoxin (lipopolysaccharide, LPS, a gut-bacteria fragment that triggers inflammation) rose after the saturated-fat meal but not after the monounsaturated-fat meal or the others (López-Moreno 2017). This trial did not use macadamias; it concerns monounsaturated fat in general.

In animals and cell culture

• In mice fed a high-fat diet, macadamia oil given by stomach tube three times a week for 12 weeks reduced fat-cell enlargement and inflammation in fat tissue and in immune cells called macrophages (Lima 2014).
• In liver cells grown in the laboratory and in mice on a high-fat diet, macadamia oil reduced fat accumulation, lowered markers of oxidative damage (malondialdehyde) and raised antioxidant enzymes such as superoxide dismutase; in the mice it also lowered blood cholesterol, triglycerides and LDL (Shuai 2023). A 2024 mouse study reported similar effects on blood lipids, liver enzymes and oxidative stress (Zhang 2024). Both groups attribute the effects to the AMPK and Nrf2 signalling pathways.

These animal and cell results used macadamia oil at doses chosen for laboratory work. None has been tested by feeding macadamia nuts to people and measuring the same markers.

Blood Vessels and the Hours After a Meal

Endothelial function

The endothelium is the thin inner lining of blood vessels. When it works well, an artery widens in response to increased blood flow. Researchers measure this with flow-mediated dilation (FMD): an ultrasound of the arm artery before and after a cuff is released. Poor FMD is an early sign of artery disease. No macadamia trial in the records gathered here measured FMD. Two trials of monounsaturated-fat diets did, with different results:

• Positive: 22 men with high cholesterol in Spain ate a diet high in saturated fat, then in random order a low-fat NCEP Step-1 diet and a Mediterranean diet rich in monounsaturated fat, 28 days each. Compared with the saturated-fat diet, FMD improved during the Mediterranean diet but not during the low-fat diet. LDL, apolipoprotein B and P-selectin (a marker of activated blood cells) fell on both (Fuentes 2001).
• Null: in a controlled-feeding crossover trial of 31 adults with or at risk of metabolic syndrome, three diets that differed only in their oil — conventional canola, high-oleic canola, or a control blend higher in saturated fat — were eaten for 6 weeks each. FMD did not differ between diets (6.32%, 6.96% and 6.41%) (Davis 2022).

After a fatty meal

Blood triglycerides rise for several hours after a meal containing fat ("postprandial lipaemia"), and a large, long-lasting rise is considered a cardiovascular risk factor in its own right. A Danish study gave a single test meal deriving 72% of its energy from monounsaturated fat, using macadamia nut oil, to 17 first-degree relatives of people with type 2 diabetes and 17 people without such a family history. Triglycerides, insulin, glucose, gut hormones (GLP-1 and GIP) and ghrelin over the following 4 hours did not differ between the two groups, although several genes in muscle and fat tissue responded differently (Pietraszek 2014). The study compared two groups of people eating the same meal; it did not compare macadamia oil with another fat, so it says nothing about whether macadamia oil produces a smaller or larger triglyceride rise than other fats.

Where Macadamias Sit in the Nut Meta-Analyses

A meta-analysis pools the results of many trials to get a more precise answer than any one of them. Because there are so few macadamia trials, the larger nut meta-analyses give the macadamia results their context.

• The network meta-analysis of tree nuts (2020). A network meta-analysis compares several treatments against each other at once. This one pooled 34 trials with 1,677 participants and ranked walnut, pistachio, hazelnut, cashew and almond diets on blood lipids. Pistachio-enriched diets ranked best for lowering triglycerides, LDL and total cholesterol, walnut second for triglycerides and total cholesterol, and almond second for LDL. The authors noted the quality of evidence was low and that the trials were few and often poorly reported. Macadamias were not among the nuts compared, so no ranking for them exists (Liu 2020).
• The largest nut-and-lipids meta-analysis (2025). 113 randomised trials in 8,060 adults, at a median of 45.5 g of nuts a day, found that nuts lowered total cholesterol by 0.14 mmol/L, LDL by 0.12 mmol/L, triglycerides by 0.05 mmol/L and apolipoprotein B by 0.04 g/L, with no significant effect on HDL. Certainty was rated moderate or low for most outcomes (Nishi 2025). One author declared research support from a nut-industry foundation and non-financial support from nut-grower organisations; the paper states these had no role in the study.
• Tree nuts and peanuts on cardiovascular risk factors (2023). 139 studies were reviewed and 129 pooled. Nut consumption significantly lowered LDL, total cholesterol, triglycerides, the cholesterol ratios and apolipoprotein B. The certainty of the evidence was rated "moderate" for the ratios and apoB, "low" for triglycerides and "very low" for LDL and total cholesterol, because results were inconsistent and publication bias was likely (Houston 2023).
• A dissenting analysis (2022). A meta-analysis using standardised effect sizes found no significant overall effect of nuts on the blood lipid profile, though it found lower total cholesterol with pistachios and higher HDL with cashews (Gunathilake 2022). PubMed lists a 2023 expression of concern linked to this paper, so its results carry an extra question mark.

The macadamia trials fit inside this picture. In Griel 2008 the LDL difference was 0.30 mmol/L; in Jones 2023 the non-significant drop was about 0.12 mmol/L (4.7 mg/dL) — close to the 2025 pooled average for all nuts. The authors of the 2023 trial made the same comparison. There is no evidence in these records that macadamias lower LDL more than other nuts despite their higher monounsaturated fat.

Replacing Saturated Fat With Monounsaturated Fat

Since the macadamia's case rests on its fat, the research on monounsaturated fat as a replacement for saturated fat is central. It is more uncertain than many summaries suggest.

On cholesterol: consistent

A 1995 meta-analysis of 14 controlled diet studies compared oils rich in monounsaturated fat with oils rich in polyunsaturated fat, keeping total fat, saturated fat, fibre and cholesterol the same. Replacing saturated fat with either type lowered total and LDL cholesterol by a similar amount — roughly 0.65 mmol/L (25 mg/dL) — and the two unsaturated fats did not differ from each other on LDL or HDL. Triglycerides were modestly lower on the polyunsaturated diets. Neither type changed HDL or triglycerides compared with the saturated-fat diets (Gardner 1995).

On heart attacks and deaths: uncertain for monounsaturated fat specifically

• Cochrane review (2020). 15 randomised trials lasting at least two years, with 56,675 participants, found that reducing saturated fat lowered combined cardiovascular events by 17% (risk ratio 0.83; 95% CI 0.70 to 0.98; moderate-quality evidence). It found little or no effect on all-cause mortality (0.96) or cardiovascular mortality (0.95). Replacing saturated fat with polyunsaturated fat or carbohydrate appeared useful, but data on replacement with monounsaturated fat were "very limited" and its effects were described as "unclear" (Hooper 2020).
• Risk-stratified review (2026). 17 trials with 66,337 participants found low- to moderate-certainty evidence that reducing saturated fat may slightly reduce all-cause mortality (risk ratio 0.96), cardiovascular mortality (0.93), non-fatal heart attack (0.86) and stroke (0.83), with confidence intervals that include no effect. For people at low baseline risk, the absolute benefit over 5 years fell below the authors' thresholds of importance; for high-risk people it exceeded them, most clearly when polyunsaturated fat replaced saturated fat (non-fatal heart attack 0.75). The authors list "data were limited on the replacement of saturated fat with monounsaturated fat" as a limitation (Steen 2026).
• Observational evidence (2014). A meta-analysis of 32 observational studies with 530,525 participants found that people with the highest monounsaturated fat intake had about the same coronary risk as those with the lowest (relative risk 0.99; 95% CI 0.89 to 1.09); for circulating monounsaturated fatty acids in blood the figure was 1.06 (0.97 to 1.17). The same analysis found no clear association for saturated fat (1.02) and a raised risk with trans fat (1.16) (Chowdhury 2014).

On blood pressure: no difference from carbohydrate

A meta-analysis of 14 trials (980 participants) found that high-monounsaturated diets, eaten in place of high-carbohydrate diets with saturated fat kept low, did not lower blood pressure more than the carbohydrate diets (systolic difference −0.08 mmHg, diastolic 0.01 mmHg; moderate-quality evidence) (Jovanovski 2019).

In short: replacing saturated fat with monounsaturated fat reliably lowers LDL in feeding studies, but direct trial evidence that this particular swap prevents heart attacks or deaths is sparse, and the reviews say so plainly. Monounsaturated fat from food sources such as olive oil and nuts has its own, separate body of outcome evidence, described next.

Heart Attacks, Strokes and Deaths: The Indirect Evidence

The FDA found no observational studies of macadamia nuts and heart disease (FDA letter, 2017), and no trial has counted cardiovascular events in people eating macadamias. The outcome evidence below concerns nuts in general, olive oil and Mediterranean-style diets.

• PREDIMED (republished 2018). 7,447 Spanish adults aged 55 to 80 at high cardiovascular risk were assigned to a Mediterranean diet with extra-virgin olive oil, a Mediterranean diet with mixed nuts, or advice to reduce dietary fat. Over a median of 4.8 years, major cardiovascular events (heart attack, stroke or cardiovascular death) occurred in 3.8% of the olive-oil group, 3.4% of the nut group and 4.4% of the control group — hazard ratios 0.69 and 0.72. The original 2013 report was withdrawn after the investigators found randomisation problems at some sites; the 2018 version re-analyses the data with methods that do not assume every participant was randomised (Estruch 2018). The withdrawn 2013 report is not cited here.
• Cochrane review of Mediterranean diets (2019). Weighing PREDIMED as re-analysed, the Cochrane authors rated the evidence low quality for cardiovascular mortality (hazard ratio 0.81; 95% CI 0.50 to 1.32) and total mortality (1.0), and moderate quality for a reduction in strokes (hazard ratio 0.60). They concluded that "there is still some uncertainty" about the effects of Mediterranean-style diets on clinical outcomes (Rees 2019).
• Nut-eating cohorts (2017). A meta-analysis of 18 prospective studies found that people eating the most nuts had a 25% lower rate of cardiovascular death (relative risk 0.75) and 27% lower coronary death than those eating the least. Peanuts (5 studies) and tree nuts (3 studies) showed similar associations, and the association levelled off at about 12 g a day (Chen 2017). Cohort studies like these show associations, not cause and effect, and none separated out macadamias.
• Olive oil cohorts (2022). Across prospective studies, each additional 25 g a day of olive oil was associated with a 16% lower risk of cardiovascular disease (relative risk 0.84) and 11% lower all-cause mortality; there was unexplained heterogeneity between studies for these outcomes (Martínez-González 2022).

These findings are often borrowed for macadamias because of the shared monounsaturated fat. Whether macadamias would show the same associations has not been studied: their saturated-fat and palmitoleic-acid content differ from olive oil's, and the PREDIMED abstract describes its nut supplement only as mixed nuts. More on PREDIMED and nuts is in Walnuts: Heart Health and PREDIMED.

The FDA Qualified Health Claim (2017)

On 24 July 2017 the FDA announced that it would exercise "enforcement discretion" for a qualified health claim linking macadamia nuts with reduced risk of coronary heart disease (FDA constituent update, 24 July 2017). The claim followed a petition filed in November 2015 on behalf of a macadamia producer. 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."

What "qualified" means

A fully authorised health claim in the US requires "significant scientific agreement." A qualified claim is used when the evidence falls short of that standard; it has to carry wording such as "supportive but not conclusive" so that the strength of the evidence is conveyed. "Enforcement discretion" means the FDA has stated it does not intend to object to the claim being used, under the conditions it set out.

How the FDA weighed the evidence

According to the FDA's response letter (FDA letter, 2017):

• It used total cholesterol and LDL cholesterol as the surrogate endpoints for coronary heart disease.
• Of five intervention studies, it could draw conclusions from three (Colquhoun 1996, Curb 2000, Griel 2008), totalling 72 participants; only Griel 2008 was rated high quality. The 2003 and 2004 studies were set aside for lacking a control group or statistical comparison.
• It found no observational studies of macadamias and heart disease.
• It concluded there is "consistent but limited scientific evidence" for the relationship "when macadamia nuts are substituted for other sources of saturated fat in the diet". The phrase "not resulting in increased intake of saturated fat or calories" was required for that reason.
• The petition did not identify a specific substance in macadamias responsible for the effect; in the studies, the nuts replaced other sources of saturated fat.

The saturated-fat exception

Heart-health claims ordinarily require a food to be low in saturated fat, and a claim is disqualified if a food carries more than 4 g of saturated fat per 50 g. Raw macadamias carry 6.03 g per 50 g, so they exceed that level. The FDA allowed the claim anyway, citing the nut's roughly 5-to-1 ratio of unsaturated to saturated fat and its fibre and phytosterols, on condition that the label carries a disclosure ("See nutrition information for total fat and saturated fat") directly beneath the claim. The FDA described the decision as consistent with the qualified claim it already allowed for walnuts, and stated that it would re-evaluate if new evidence emerged.

The claim covers whole or chopped macadamias that are raw, blanched, roasted, salted or unsalted, or lightly coated or flavoured. The 2023 Jones trial, published after the FDA review, is the only macadamia trial since then in the records gathered here; it tested macadamias added to the diet without reducing saturated fat, and its cholesterol changes were not statistically significant.

What Is Not Known

• Hard outcomes. No study has measured heart attacks, strokes or deaths in people eating macadamias, and no cohort study has looked at macadamias separately.
• Long-term effects. The longest macadamia trial lasted 8 weeks. Whether the LDL change persists over years is unknown.
• Small numbers. About 125 people in total have been studied in the trials with reported sizes, in Australia and the US. The evidence is too thin for subgroups — women versus men, older adults, people with diabetes or familial hypercholesterolaemia.
• Smaller amounts. The FDA noted there are no dose-response data below 1.5 oz (42.5 g) per 2,100 kcal, so the effect of a smaller daily portion is uncertain.
• The palmitoleic acid effect. One 1994 trial suggests palmitoleic acid acts like a saturated fat on LDL. Whether that blunts the effect of whole macadamias has not been tested directly.
• Newer markers. Apolipoprotein B, LDL particle number, lipoprotein(a), CRP and endothelial function have not been reported from a macadamia-only trial in the records gathered here.
• Head-to-head comparisons. No trial in these records compared macadamias directly with olive oil or with another nut.
• Funding. The funding of the macadamia trials is not stated in their abstracts.

Who the Research Raises Concerns For

• People with tree-nut allergy. Macadamia allergy is classed with tree-nut allergy. A review notes that tree-nut allergies usually begin in childhood, rarely fade, and are one of the main causes of fatal allergic reactions in children and adults (Kuźmiński 2021).
• Calorie and fat content. USDA lists 718 kcal per 100 g, about 201 kcal per ounce. The trials gave large portions, and the FDA claim is worded around macadamias not increasing total calories or saturated fat. The 2023 trial found no significant weight gain over 8 weeks when nuts supplied about 15% of calories (Jones 2023).
• Saturated fat. Macadamias carry more saturated fat than other common nuts, which is why the FDA requires the saturated-fat disclosure.
• Salted, sugared and chocolate-coated versions. The trials used plain nuts. The FDA letter notes that the sodium disqualifying level for a health claim is 480 mg per reference serving; chocolate-coated macadamias are a different food in terms of sugar and saturated fat.
• Dogs. Macadamias are toxic to dogs, though not to people — see the main Macadamias page.

Decisions about cholesterol treatment, including diet changes for people on lipid-lowering medicines, belong with a clinician. Reading a cholesterol result is covered on Lipid Panel.

Connections

• Nuts — the nuts landing page
• Macadamias — the main topic page
• Macadamias — Benefits Deep Dive — the hub for these articles
• Palmitoleic Acid and Metabolic Health — the omega-7 fat in depth
• Oil, Tocotrienols and Oxidative Stability — why macadamia fat resists rancidity
• Macadamias: Nutrient Profile — the full USDA table
• Nut Benefits — the evidence across all nuts
• Avocado: Monounsaturated Fats — the other monounsaturated whole food
• Olive Oil — the best-studied oleic-acid food
• Olive Oil: Heart Health — the outcome evidence for olive oil
• Almonds: Heart Health and LDL — a nut with far more trials
• Walnuts: Heart Health and PREDIMED — the nut arm of PREDIMED
• Peanuts: Heart Health and Mortality — the cohort evidence
• Mediterranean Diet — the dietary pattern behind the outcome trials
• Cholesterol Management — the condition these trials target
• Atherosclerosis — what LDL is ultimately linked to
• Coronary Artery Disease — the disease named in the FDA claim
• Lipid Panel — LDL, HDL and triglycerides explained
• ApoB — the particle count the nut meta-analyses report
• Trans Fats — the fat with the clearest coronary risk

Key Research Papers

1. 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
2. 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
3. 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
4. Nora CL, Zhang L, Castro RJ, et al. Effects of mixed nut consumption on LDL cholesterol, lipoprotein(a), and other cardiometabolic risk factors in overweight and obese adults. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2023;33(8):1529-1538. PubMed PMID: 37263914
5. 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
6. 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
7. 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
8. Liu K, Hui S, Wang B, et al. Comparative effects of different types of tree nut consumption on blood lipids: a network meta-analysis of clinical trials. The American journal of clinical nutrition. 2020;111(1):219-227. PubMed PMID: 31773150
9. 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
10. Houston L, Probst YC, Chandra Singh M, et al. Tree Nut and Peanut Consumption and Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Advances in nutrition (Bethesda, Md.). 2023;14(5):1029-1049. PubMed PMID: 37149262
11. Gunathilake M, Van NTH, Kim J. Effects of nut consumption on blood lipid profile: A meta-analysis of randomized controlled trials. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2022;32(3):537-549. PubMed PMID: 35144856 (subject of a 2023 expression of concern)
12. 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
13. 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
14. Steen JP, Klatt KC, Chang Y, et al. Effect of Interventions Aimed at Reducing or Modifying Saturated Fat Intake on Cholesterol, Mortality, and Major Cardiovascular Events : A Risk Stratified Systematic Review of Randomized Trials. Annals of internal medicine. 2026;179(2):242-255. PubMed PMID: 41397264
15. 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
16. Jovanovski E, de Castro Ruiz Marques A, Li D, et al. Effect of high-carbohydrate or high-monounsaturated fatty acid diets on blood pressure: a systematic review and meta-analysis of randomized controlled trials. Nutrition reviews. 2019;77(1):19-31. PubMed PMID: 30165599
17. Fuentes F, López-Miranda J, Sánchez E, et al. Mediterranean and low-fat diets improve endothelial function in hypercholesterolemic men. Annals of internal medicine. 2001;134(12):1115-9. PubMed PMID: 11412051
18. Davis KM, Petersen KS, Bowen KJ, et al. Effects of Diets Enriched with Conventional or High-Oleic Canola Oils on Vascular Endothelial Function: A Sub-Study of the Canola Oil Multi-Centre Intervention Trial 2 (COMIT-2), a Randomized Crossover Controlled Feeding Study. Nutrients. 2022;14(16). PubMed PMID: 36014910
19. López-Moreno J, García-Carpintero S, Jimenez-Lucena R, et al. Effect of Dietary Lipids on Endotoxemia Influences Postprandial Inflammatory Response. Journal of agricultural and food chemistry. 2017;65(35):7756-7763. PubMed PMID: 28793772
20. 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
21. Rees K, Takeda A, Martin N, et al. Mediterranean-style diet for the primary and secondary prevention of cardiovascular disease. The Cochrane database of systematic reviews. 2019;3(3):CD009825. PubMed PMID: 30864165
22. Chen GC, Zhang R, Martínez-González MA, et al. Nut consumption in relation to all-cause and cause-specific mortality: a meta-analysis 18 prospective studies. Food & function. 2017;8(11):3893-3905. PubMed PMID: 28875220
23. Martínez-González MA, Sayón-Orea C, Bullón-Vela V, et al. Effect of olive oil consumption on cardiovascular disease, cancer, type 2 diabetes, and all-cause mortality: A systematic review and meta-analysis. Clinical nutrition (Edinburgh, Scotland). 2022;41(12):2659-2682. PubMed PMID: 36343558
24. 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
25. 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
26. 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
27. Kuźmiński A, Przybyszewski M, Przybyszewska J, et al. Tree nut allergy. Postepy dermatologii i alergologii. 2021;38(4):544-549. PubMed PMID: 34658691

PubMed Topic Searches

1. Macadamia nuts and cholesterol
2. Macadamia randomised trials
3. Replacing saturated fat with monounsaturated fat
4. Palmitoleic acid and LDL cholesterol
5. Nut consumption and blood lipids: meta-analyses
6. Monounsaturated fat and endothelial function

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