Roasting nuts can cause some loss of nutrients, depending on the type of nut, the roasting temperature, and the roasting time. However, the amount of nutrient loss is generally not significant, and some nutrients may even become more available after roasting.
For example, roasting nuts can increase their antioxidant activity and make some nutrients, such as vitamin E, more bioavailable. On the other hand, roasting nuts can also cause some loss of heat-sensitive nutrients, such as vitamin C and some B vitamins, if they are roasted at high temperatures or for too long.
The extent of nutrient loss also depends on the type of nut. Some nuts, such as almonds and pistachios, are more resistant to nutrient loss during roasting, while others, such as walnuts and pecans, are more vulnerable.
In general, roasting nuts at a moderate temperature (around 300°F to 350°F) for a short time (less than 20 minutes) can help preserve their nutrient content while enhancing their flavor and aroma. It's also a good idea to consume roasted nuts in moderation as part of a balanced diet, as they can be high in calories and fat.