Guidelines and Precautions. The jury is still out on melatoninâs effects on blood pressure. If you have high or low blood pressure, or take medications to control your blood pressure, it is best to avoid the supplement unless advised otherwise by your doctor.uidelines and Precautions. The jury is still out on melatoninâs effects on blood pressure. If you have high or low blood pressure, or take medications to control your blood pressure, it is best to avoid the supplement unless advised otherwise by your doctor.
1 This can cause the can to bulge or rust.  Use canned tuna by the expiration date on the can. If the can doesn't have a best by date, mark it with the date of purchase and use the tuna within 12 to 24 months of purchase.
Canned seafood is best only frozen for two months but you must decant into different containers as it is not advised to freeze cans. For dairy and egg products, butter can keep for up to nine months in the freezer whilst margarine can last for up to a year.