NutritionData says that 1 ounce of raw whole almonds, about 23 nuts, provides 162 calories, 117 of those calories (72%) coming from fat. As we’ve seen , that’s not how many calories or how much fat we get when we eat them. (See: We Absorb Fewer Calories When We Eat Whole Foods – The Case Of Almonds). That study found that almonds’ calories are overestimated by up to 32% since our digestion is not 100% effective at releasing nutrients, e.g. fat, from the almonds before they exit our body.
Here’s a new study from London that provides more evidence for this:
Effect Of Mastication On Lipid Bioaccessibility Of Almonds In A Randomized Human Study And Its Implications For Digestion Kinetics, Metabolizable Energy, And Postprandial Lipemia, American Journal of Clinical Nutrition, January, 2015
Conclusions: Following mastication, most of the almond cells remained intact with lipid encapsulated by cell walls. Thus, most of the lipid in masticated almonds is not immediately bioaccessible and remains unavailable for early stages of digestion. The lipid encapsulation mechanism provides a convincing explanation for why almonds have a low metabolizable energy content and an attenuated impact on postprandial lipemia.
The subjects chewed raw or roasted whole almonds, then spit them out. These were young, healthy subjects whose chewing apparatus was intact. Upon analysis, only 8.5% and 11.3% (raw and roasted) of the fat in the almonds was released by chewing.
If a 1 ounce serving of raw almonds has 14 grams of fat, only 1 gram of that fat (8.5%) was liberated for absorption via chewing in this study. You read that right.
“In the present study, we have shown that the proportion of lipid released from the almonds following mastication is severely limited.”
There’s something else going on … When the pieces of food we swallow after chewing are large (in the range of 1 to 2 millimeters), it delays emptying of the stomach…
“… because [these pieces] cannot pass through the pylorus (the so-called sieving effect), inducing a feeling of fullness and lower subsequent energy intake.”
So, not only do the almonds themselves not provide as many calories and as much fat as we’d expect, but eating them causes us to feel full and eat less, assisting weight loss.
In conclusion, we have developed a new method for determining lipid bioaccessibility of masticated almonds, showing that most lipid (∼89–92%) is retained within the tissue matrix (i.e., as intracellular lipid). An encapsulated lipid mechanism provides a plausible explanation of why almonds elicit a low postprandial lipemic response and have a low metabolizable energy content despite their status as a high energy density food. This mechanism may also partly explain the sustained weight loss induced by an almond-enriched diet.
Perhaps this is why the men in that pistachio study could add – a pure add, not a substitution – 120 whole pistachios a day to their diets and not gain weight or increase their BMI or waist circumference. Nuts, as we’re coming to learn, especially raw, whole nuts have an undeserved bad reputation among dieters.