It's important to eat fruits and veggies...pretty much any way you can. However, here are some tips to get the most nutritional value out of your produce, if you can.
1. Eat Fresh-Picked (Local/Homegrown)
When buying vegetables, try not to buy them more than a few days ahead of when you're planning to serve them. In fact, freshness is so important that it's better to buy from a farmer's market where they have just been picked, than to buy organic from a grocery store.
Some vegetables, such as carrots, will be higher in nutrients when originally cut. It's that cutting into the carrot causes it trauma, which triggers the carrots to release more nutrients as a sort of protective measure, much like our adrenaline goes up if we get hurt. Until you're ready to cook or serve the vegetables, store them in the new Green Bags or Green Containers. These storage pieces keep fruit and vegetables fresh longer by trapping gasses in them and away from the foods.
Heat can destroy nutrients in vegetables so make sure that if you are going to cook them, you do so for only a limited amount of time and with minimal amount of water. For this reason, steaming is much better than boiling (unless making soup and will keep the water--which retains all the nutrients). Stir-frying is excellent, just don't overdo the oil. Roasting is also a good method, compared to boiling. It preserves nutrients, and only minimal amounts are lost from the high temperatures.
The vegetables should not be soft and soggy. Their texture should be soft but still with a snap to them. Aside from potatoes, carrots, and corn, for example, most other vegetables like squash, cauliflower, broccoli, and onions, shouldn't be cooked for any more than 5 to 6 minutes. The harder vegetables take around 20 minutes on average. Make sure that you wash vegetables thoroughly in fresh cool water using a brush when needed. There are even vegetable rinses that you can buy for cleaning them
While there are many vegetables that are most nutritious when eaten raw, there are a couple that actually gain more nutrition from being heated and/or cooked. Carrots are one such example and although the tomato is technically a fruit, it is include here and noted that cooked tomatoes are more nutritious than raw. (Green beans and celery also can be enhanced in nutritional value when cooked)
*(I always roast a big batch of carrots to have during the week: cut into little sticks, add 1-2 T oil and minced garlic, then sprinkle with a little salt and pop in the oven on a tray for about 30 minutes at 350 degrees. We prefer to eat carrots this way--and they don't make my husband's throat itch as much this way, as opposed to the raw).
Another tip is to add flavors to the steam water to infuse your vegetables as they cook. Ex: soy sauce or lemon juice. Or add honey to steamed/sauteed orange vegetables.
3. To peel or not to peel?When you peel the outer skins from vegetables, you are throwing away many of the nutrients the food contains. It's best to scrub the outer skin and leave it on for cooking and eating to get the most health benefits. But, obviously organic peels are much better to eat than non-organic. If you want higher nutrient content with the least amount of chemicals, opt. for organic and unpeeled.
4.There are a couple of vegetables that when combined become a lot healthier; one example of this is broccoli and tomatoes. They taste great together and provide protection against prostate cancer. What and how you serve your vegetables is also important for nutrition and making healthy meals. Thick heavy sauces and sugars may taste good but will not be good choices. Using vegetables in salads with some flax seed, extra virgin olive oil and balsamic vinegar would be a much more healthy choice.