Nuts are high in fibre, low in saturated fats, high in beneficial unsaturated fats and very high in antioxidants.
Walnuts in particular have the highest concentration of polyunsaturated fatty acids and are a great vegetarian source of omega-6 and omega-3 fats.
Walnuts contain significantly higher amounts of polyphenols (a type of antioxidant) compared to an equivalent serving of other types of nuts- including Brazil, pistachio, pecan, peanut, almond, macadamia, cashew and hazelnuts.
A study published in Biology of Reproduction examined 117 healthy men, half of whom were asked to eat 75 grams of walnuts a day, as well as their usual diet
Semen and blood samples were collected before and after the 12 week intervention. The men who consumed walnuts saw significant improvement in sperm vitality, motility and morphology compared to the men who did not consume walnuts or other tree nuts.
They also found that circulating blood levels of omega-3 and omega-6 fats- were higher in the walnut eaters after the 3 month study.
The fertility study mentioned above chose the daily amount of 75 grams of walnuts because previous research has shown this amount can be expected to alter blood fat levels but not trigger weight gain.
A serving of 75 grams of shelled, whole walnuts is approximately one large handful, or 18- 20 nuts.