Nuts are a very healthy food to be eating and are actually associated with better weight control. Scientists have confirmed that the available energy from walnut is much less than expected.

One of the reasons that may explain this (despite their high fat content) is that the available energy from nuts is much less than would be predicted. Almonds have been measured at 20 percent less.

Researchers have now put walnuts to the same test. Under controlled dietary conditions, 18 healthy adults followed a dietary plan for two different three week periods. One of the dietary plans included the addition of 42 grams of walnuts each day.

The energy contained in all of the food eaten was analysed in a laboratory while urine and faecal samples were also analysed to see how much of the potential energy from the food was lost from the body.

It was found that the metabolisable energy of the walnuts was 21 percent less than predicted. The reason for less available energy was from fat being trapped inside the plant cell wall, limiting accessibility by digestive enzymes.

This may be more pronounced if the nuts have not been chewed fully.

Sorry peanut butter lovers, but the same ‘energy tax’ from whole nuts would not apply to the highly homogenised spread.

Implications

While there isn’t a lot of research in the area, there is a case to put forward that the energy labelling of foods likely over-estimates foods that are mostly whole (especially plant foods). This is because of the reduced availability of nutrients in the food from being trapped within the cell walls.

You do not get the same ‘benefit’ (in an environment today where over-eating is a big problem) from eating very processed food.

Last Reviewed: 27/08/2019

© Norman Swan Medical Communications.



References

Baer DJ et al. Walnuts consumed by healthy adults provide less available energy than predicted by the Atwater factors. Journal of Nutrition 2016;146:9-13.