I had a great question the other day as I sat eating lunch next to two lovely women at the Peacefood cafe. (Try the dumplings!) One of the women was saying how she liked the articles she saw about different foods and their benefits for us, but that they never say how much to take. The good news is that a little goes a long way.
Turmeric is a good example as it turns up on lists and articles all the time. Turmeric is a fantastic anti-inflammatory and works great for arthritis. It's been studied and seems to not just help with memory but can fight off Alzheimer's disease too. So how much is enough? For most people, just a 1/4 teaspoon per week can be enough. Check your vitamin pill if you take one, I bet it's in there. The more conditions you are currently suffering with that it can help with, the more you might want to add in.
Cranberry juice is not good at clearing a UTI, just 1/4 cup of the full on pressed juice, (I would dilute with water for an enjoyable beverage.) can help you lose some fat and clear out bad bacteria. If you have a uti than of course drinking as much as you like will clear things faster.
Kiwi's are full of vitamin C and just one little green fruit is enough for the day.
Some things work better when you are consistent. Take wild oregano oil for example. You only need a few drops to kill a cold or eliminate allergy symptoms but being consistent and doing a few drops each day or twice day seems to to have an accumulative effect where it works better the longer you take it.
Use your common sense and your own intuition. There is no perfect and right answer to how much of anything to eat because each person is a different size, shape and has different things going on. Learn the benefits of the foods so that you can make informed guesses and experiment within reason. If you need some guidance, book a session.