Port wine is wine that has been fortified with grape spirit partway through the fermentation process. This stops the fermentation process, which is why some port wines tend to be sweet, because not all of the sugar gets fermented into alcohol.
Whether or not you want to include that sugar (or alcohol, for that matter) in your diet depends entirely on your personal reaction to sugar and alcohol. If you can handle a little as the occasional treat, then go for it. If you find it makes you feel fuzzy or a little off, then you should probably avoid it.
The Health Benefits
If you haven’t noticed any ill effects from the occasional dessert wine, there are some noted health benefits to drinking it. First of all, it’s a blood thinner, which lowers the risk of heart disease. It has also been shown to improve cholesterol levels and immune function. For this reason, Mark Sisson even gave wine smart fuel status.