Lots of nutritional advice in America is suspect because someone is marketing a product. And the Old Country ways of eating are either lost in the New World, or don't work sometimes because we've switched from manual labor to desk jobs. And on top of that, are you trying to optimise for athletic performance, longevity, or are you just enjoying life?
(I don't think those three are necessarily mutually exclusive, but I do wonder about the modern obsession of over-optimisation.)
- https://examine.com (each article is well sourced)
- Canadian Government: http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/index-eng.ph...
- US Government: https://health.gov/dietaryguidelines/ (I'm more skeptical of USDA's https://www.nutrition.gov/)
There are lots of different dietary protocols (keto, vegan, etc etc) that various people swear by. So, your question is simply too broad to answer with more than very broad guidelines about what kind of website to look for when searching.
One of my main go-to databases has become nutritiondata.com, which gives overviews of the nutrition information in pretty impressive detail on just about any dish or ingredient you can imagine.
I also really like Rhonda Patrick's Youtube channel.
If you get regular blood panels, you can usually find what you're deficient in and adjust your diet accordingly.
Cronometer is great for tracking micronutrient intake.
In general though, Michael Pollan's advice is usually enough. "Eat food. Mostly plants. Not too much."