A strange co-incidence exists: walnut kernels look like a brain and are super good for one's brain.
Evidence-based health benefits of eating walnuts with accurate scientific references
(1.) Walnuts as a brain superfood
Organic Kashmiri walnuts have been shown to improve the cognitive and memory functions of individuals in numerous studies.
Consumption of walnut kernels can lead to a significant reduction in oxidative stress which further assists in slowing the ageing process and the probability of Alzheimer's disease. 
Kashmiri walnuts help reduce amyloid plaque in human brains resulting in improved brain health. 
Studies have also shown walnuts to boost brain health and function even with age!. 
Regular consumption of walnuts by adults results in significant improvement in cognitive function, regardless of age or gender. 
Soaked walnuts are a great source of omega 3 and 6 fatty acids, as well as a whole host of other great nutrients.
(2.) Healthy for one's gut (the second brain)
It's well known that after the human brain, the gut has the maximum nerve endings. The health of the gut determines one general well being and one's mood, giving it the name: the second brain.
194 adults ate 43 grams of walnuts daily for eight weeks which resulted in a significant increase of good bacteria in their gut. 
No wonder, a small cup of organic Kashmiri walnuts daily at breakfast with cereal or just as a snack, makes an extremely healthy option.
Walnuts help in creating a healthy composition of the gut microbiota resulting in overall better health and mood.
(3.) Supports weight management
In a controlled study involving 10 obese adults, drinking a smoothie with 48 grams of walnuts daily for 5 days decreased their appetite and hunger as compared to a placebo drink with similar nutrients and calories. 
Moreover, this boon of weight management can lead to controlled blood pressure.
(4.) Controls Type-2 diabetes and reduces risk
In a controlled study in 100 people with type 2 diabetes, consuming 1 tablespoon of walnut oil a day for 3 months, while continuing their usual diabetes medication and balanced diet, resulted in an 8% decrease in fasting blood sugar 
Thus, adding a handful of organic Kashmiri walnuts to one's diet over time can lead to controlling and reducing risk of diabetes.
5.) Strengthens male reproductive health
Regular consumption of walnuts may help support sperm health and male fertility.
177 men who ate 75 grams of walnuts daily for 3 months had improved sperm shape, vitality and mobility compared to males who did not eat nuts. 
Studies also show that eating walnuts result in reduction of oxidative stress of membranes of the male sperm resulting in better sperm health.
What type of walnuts are available online?
One finds a large variety of walnuts online: Chilian, Californian, Organic Kashmiri and most recently Chinese walnuts.
Off all the above varieties, the organic Kashmiri walnuts from India have the highest PUFA (good fat) content and a distinct old-school nutty flavour, primarily owing to its organic, sometimes almost wild-like cultivation.
The difference between Kashmiri walnuts viz. Chiliean and Californian walnuts is manner of cultivation along with the strain being indigenous and not hybrid, results in the Kashmiri walnut having a very distinct flavour compared to its imported counterparts in the dry-fruit market.
Though they make up a small fraction of the global walnut produce, the top varieties of the Kashmiri walnut, such as the extra-light Kagzi walnut kernels, are the most sought after walnuts at luxury gourmet stores across the western world.
To obtain the freshest and tastiest kernels, i.e. the light and the extra-light ones, an exhaustive manual sorting of the walnuts is carried out followed by state-of-the-art vacuum packaging - an exercise carried out daily at Aagur ensuring freshness, the old-school nutty taste of Kashmiri walnuts with guaranteed 0% bitter pieces.
Index of scientific papers used in the article on health benefits of walnuts above:
 Role of Walnuts in Maintaining Brain Health with Age by Shibu M. Poulose (USDA), Marshall G. Miller (Duke University) and Barbara Shukitt-Hale (Tufts University)
 A Walnut-Enriched Diet Affects Gut Microbiome by Charlotte Bamberger, Andreas Rossmeier, Katharina Lechner, Liya Wu, Elisa Waldmann, Sandra Fischer, Renée G Stark, Julia Altenhofer, Kerstin Henze, Klaus G Parhofer
 The Effect of Walnut Oil Consumption on Blood Sugar in Patients With Diabetes Mellitus Type 2 by Mohammadjavad Zibaeenezhad, Kamran Aghasadeghi, Hossein Hakimi, Hassan Yarmohammadi, Farzad Nikaein