Humans have traditionally eaten foods grown locally and seasonally. However, modern technology has changed that natural way of eating and today every type of food is available at any time of the year regardless of the season or area where it is grown.
Unfortunately, poor health can result from consistently eating foods outside of our climate and season. According to John Matsen, ND, "All plants contain potassium. Generally, the more sun they're exposed to, the more potassium and sugar they contain... The high potassium and sugar levels alert your kidneys that you're out in the hot sun (because these foods grow in sunny climates), and that your skin must be making lots of Vitamin D. Therefore, your kidneys don't activate vitamin D, and you don't absorb much calcium. This results in low calcium levels, forcing the body to take calcium from other sources such as bones, teeth and membranes, thus weakening those structure." 1
The above basically means a tropical fruit like a banana, when eaten in a temperate climate (USA) could potentially lead to bone loss. Egads!
From another health perspective Traditional Chinese Medicine (TCM) teaches that salads and fruits are cooling to the body. During the hot summer months that cooling effect can be beneficial to the body, but during the cold winter season, it can weaken the digestive system, contribute to candida yeast, gas, bloating and an inability to warm up (cold hands and feet). If you are one of those folks that goes to bed with mittens and socks on.... you could be eating the wrong type of foods. A simple remedy would be to change your food choices during specific times of the year and get in harmony with the seasons.
To function optimally, your body (and mind) needs to become aligned with the seasons and climate you live in. It's easy to discover what's available at various times of year and in your particular climate by visiting a local farmer's market.
You could also join a community supported agriculture (CSA) and get fresh produce, fruit and livestock products direct from the farmer once per week at a designated pick-up site. Check out justfood.org and localharvest.org to find a CSA or farmer's market near you. Trust me...your beautiful body, digestive system and bones will love you for it!

1. Better Nutrition Magazine, September 2004, pg. 30