In the news: Walnuts for Mental Sharpness? Dark Chocolate May Benefit the Eyes

Can Walnuts for Breakfast Boost Brain Power?

Walnuts are chocked full of important nutrients including omega-3 fatty acids, fiber, and protein, as well as vitamins and minerals such as vitamins B1 and B6, potassium and magnesium.

Nuts in general and walnuts in particular have been linked to benefits such as reducing inflammation, promoting heart health and helping one to feel fuller.

But can walnuts also sharpen the mind when included in a breakfast meal? The results of a pilot investigation by researcher in the UK suggests that they might(1) .

The study included 32 healthy adults (18-30 years of age) who were given either a walnut-rich breakfast or a control breakfast, then crossed-over to receive the other intervention on a separate day.

The test breakfast consisted of walnuts, muesli cereal, and vanilla yogurt. The control meal was the same, but without walnuts and with more cereal and added butter so that calories would be the same for both meals.

After each breakfast, brain activity was monitored at 2,4 and 6 hours using EEG as the participants completed a number of cognitive tests. EEG measures electrical activity of the brain.

With the walnut supplemented breakfast, faster reaction times throughout the day were seen when tested for executive function tasks – skills like planning and problem-solving. Memory recall was better only at six hours after the walnut breakfast.

The changes in neural activity observed in the EEG recordings indicate that walnuts could help the brain work more efficiently during mentally challenging tasks.

Analysis of blood samples taken from participants showed lower levels of circulating fatty acids and slight increases in glucose availability with added walnuts—changes that can impact brain function, as the brain primarily uses glucose as fuel.

The authors point out that more research is needed, both to better understand how walnuts might be working and to see if their effects last over time.

The study tested 50 grams of walnuts which is equivalent to about 1/3 cup chopped nuts. So, you don’t need to add a lot of walnuts should you want to try adding them to an early meal.

It’s probably best to limit intake to ½ cup or a handful of nuts per day. That’s because nuts are calorie-dense, meaning that a small amount packs a sizeable amount of calories. One added benefit, however, is that walnuts are filling, so you might feel fuller longer.

Dark Chocolate Benefits the Eyes?

Last November’s Staying Healthy featured a study showing that dark chocolate might lower the risk of type 2 diabetes. Another recent study suggests that the eyes might also benefit from dark chocolate with its anti-inflammatory flavanol content.

The study(2) – which used state of the art imaging techniques – explored the effects of dark and milk chocolates on the anatomy and function of retinal vessels in healthy individuals.

Participants received either 20 g of dark chocolate (400 mg of flavanols) or 7.5 g of milk chocolate (very low cocoa and flavanols) then crossed over one week later to receive the opposite chocolate intervention.

Only the dark chocolate led to an increase in the dilation of retinal arteries. Arterial dilation in the retina is crucial for maintaining adequate blood flow and oxygen delivery to retinal tissues, and it's a key part of the retina's ability to adapt to changing metabolic demands and conditions.

Twenty grams of dark chocolate is roughly equivalent to 2-3 squares of a standard chocolate bar: an eye-friendly snack.

References

1. Bell L, et al. The impact of a walnut-rich breakfast on cognitive performance and brain activity throughout the day in healthy young adults: a crossover intervention trial. Food Func. 16:1696-1707, 2025.
2. Sacconi R, et al. Benefits of dark chocolate intake on retinal vessels functionality: a randomized, blind, crossover clinical trial. Sci Rep. 14:20203, 2024.