Macadamia benefits: one trial lowered cholesterol and one did not — the difference was saturated fat

Key benefits

1. 01Early research

   It moved when saturated fat was swapped — not when nuts were merely added

   Two randomised trials that fed people macadamias give different answers. The difference between them is the point of this entry.

   2008, The Journal of Nutrition.

   • 25 mildly hypercholesterolaemic people (15 women, 10 men), randomised crossover controlled feeding, five weeks per diet
   • Macadamia diet (MAC): 42.5 g (1.5 oz) per 2,100 kcal. 33% total fat, 7% saturated, 18% monounsaturated, 5% polyunsaturated
   • Average American diet (AAD): 33% total fat, 13% saturated, 11% monounsaturated, 5% polyunsaturated

   Outcome	Macadamia diet	American diet
   Total cholesterol	4.94 mmol/L	5.45 mmol/L	p<0.05
   LDL cholesterol	3.14 mmol/L	3.44 mmol/L	p<0.05
   Non-HDL cholesterol	3.83	4.26	p<0.05
   Total:HDL ratio	4.60	4.89	p<0.05
   LDL:HDL ratio	2.91	3.09	p<0.05
   Triglycerides	unchanged

   In mg/dL the total cholesterol gap is about 20 mg/dL and the LDL gap about 12 mg/dL. Not small.

   2023, Journal of Nutritional Science.

   • 35 adults with abdominal obesity, randomised crossover, eight weeks each, two-week washout
   • Free-living. Macadamias added to the usual diet at about 15% of daily calories
   • Body composition by bioelectrical impedance, intake by 24-hour recalls

   Outcome	Result
   Weight, BMI, waist, percent body fat	no significant change
   Glycaemic measures	no significant change
   Total cholesterol	−2.1% (−4.3 mg/dl, 95% CI −14.8 to 6.1) — not significant
   LDL cholesterol	−4% (−4.7 mg/dl, 95% CI −14.3 to 4.8) — not significant
   Total fat and MUFA intake	increased
   Saturated fat intake	unaltered

   Both confidence intervals cross zero. In this trial macadamias did not move the lipids.

   So why the different answers?

   First, the comparator differs. The 2008 trial measured a macadamia diet against a 13%-saturated-fat diet. What it shows is the result of taking saturated fat from 13% down to 7%. The 2023 trial laid macadamias on top of the usual diet, and saturated fat intake stayed put.

   Second, the authors said so themselves. The closing sentence of the 2008 paper reads:

   Nuts as an isocaloric substitute for high SFA foods increase the proportion of unsaturated fatty acids and decrease SFA, thereby lowering CVD risk.

   That is not a sentence about macadamias being special. It is a sentence about displacing saturated fat.

   Third, the 2023 trial carries a footnote of its own. The cholesterol lowering was larger in those with overweight rather than obesity, and in those below the median percent body fat. But that is a post-hoc split, and the overall result was not significant.

   The honest conclusion:

   • Use macadamias to replace fatty snacks or high-saturated-fat foods and the lipids may improve
   • Simply add them to what you already eat and, as the 2023 trial showed, the lipids will probably stay where they are
   • The trials held 25 and 35 people. Small
   • The grade here is "early research"

   [1][2]
2. 02Nutrition data

   75.8 g of fat, the most of any common nut — yet a fiftieth of an almond's vitamin E

   Per 100 g of raw macadamias:

   • 718 kcal — the highest of the common nuts
   • Fat 75.8 g — saturated 12.1 g, monounsaturated 58.9 g, polyunsaturated 1.5 g
   • Fibre 8.6 g, carbohydrate 13.8 g, sugar 4.57 g
   • Protein 7.91 g
   • Vitamin B1 (thiamin) 1.2 mg, manganese 4.13 mg
   • Magnesium 130 mg, copper 0.756 mg, potassium 368 mg, iron 3.69 mg
   • Vitamin E 0.54 mg, sodium 5 mg, cholesterol 0

   Per handful (30 g, about twelve nuts):

   	100 g	A handful (30 g)
   Energy	718 kcal	215 kcal
   Fat	75.8 g	22.7 g
   Monounsaturated	58.9 g	17.7 g
   Fibre	8.6 g	2.6 g
   Vitamin B1	1.2 mg	0.36 mg

   The 58.9 g of monounsaturated fat is what this nut is. About 78% of its fat is monounsaturated — the same family as olive oil's main component, and the highest such proportion among the common nuts.

   Vitamin B1 is 1.2 mg. Adult requirements sit around 1.2 mg for men and 1.1 mg for women, so 100 g covers more than a day. Even a handful gives 0.36 mg, roughly 30% of a day. That is a standout number among nuts.

   Manganese at 4.13 mg is also high, above the adequate intake of about 4.0 mg for men and 3.5 mg for women.

   But vitamin E is 0.54 mg. This is where the balance belongs. Almonds hold about 25 mg per 100 g. Macadamias are not a vitamin E source. The generalisation that nuts are rich in vitamin E does not hold for this one.

   The 718 kcal has to be taken as it is, the highest of the common nuts:

   Nut	Energy	Fat
   Macadamia	718 kcal	75.8 g
   Walnut	654 kcal	65.2 g
   Pine nut	673 kcal	68.4 g
   Almond	579 kcal	49.9 g

   A handful is 215 kcal, about two-thirds of a bowl of rice. Count them.

   The shell is hard. Macadamia shells are among the hardest of any nut and resist cracking by hand; what you buy is almost always already shelled.

   Store them sealed and refrigerated. All that fat goes rancid quickly. Discard them if they taste bitter or soft.

3. 03Not established

   The weight worry the evidence answers, and the danger it confirms — for dogs

   Two separate things here: a worry the evidence contradicts, and a hazard the evidence confirms.

   First, weight. At 718 kcal per 100 g, worrying about weight gain is reasonable.

   The 2023 trial looked at exactly that. Thirty-five adults with abdominal obesity spent eight weeks adding macadamias at 15% of daily calories to their usual diet. Adding, with nothing taken away.

   No significant change in weight, BMI, waist circumference or percent body fat.

   The paper's summary sentence is that daily macadamia consumption does not lead to gains in weight or body fat under free-living conditions in overweight or obese adults.

   Let us not overstate it. Thirty-five people, eight weeks. And the result does not mean the calories do not count. Nuts are filling, take time to chew, and some of their fat stays trapped in cell walls and passes through — that is the usual explanation. Eating from the bag without counting is a different matter.

   Now the confirmed hazard — do not give them to dogs.

   Macadamias are established as toxic to dogs. Within roughly twelve hours of eating them dogs typically show hind-limb weakness, an unsteady gait, vomiting, tremors and fever. The responsible compound has not been identified. Most recover within a few days, but a dog showing symptoms needs a vet.

   This is separate from the human story. No comparable reaction has been reported in people. But it genuinely matters to anyone who keeps macadamias at home, and it is routinely left out of articles about them. Treat it the way you treat chocolate and dogs.

   With a tree nut allergy, macadamias belong on the list. If you have reacted to another nut, be careful the first time.

How to eat it well

What to watch out for