Just depends on how low a person wants to go. For a person otherwise healthy 50 grams a day should lose weight if they need to lose weight. If a person is trying specifically for ketone production 50 grams should get a metabolically healthy person there at least part of the time. 20 grams would have them in ketosis most of the time. for a person insulin resistant or diabetic type II it takes probably no more than 20 grams just to stay in ketosis part of the time and to get insulin levels low enough to lose weight. Insulin is the key to weight loss. High insulin levels and a person can not lose weight. Carbs raise insulin in a normal person and an insulin resistant or diabetic type II insulin remains high all the time unless they get the carbs super low.

So it all depends on what a person is trying to do. For a metabolically healthy person that does not need to lose weight around 100 grams carbs a day would be a good level for someone. If a person follows the standard American diet and tries to get all the veg, fruit and whole grains they recommend they will be somewhere around 300 grams. That is without any junk food. Add some junk food and sodas in there and a lot of people probably consume 500 or more grams carbs a day and that is why they are sick and over weight.

A person can use half and half if they are not trying to keep the carbs to a minimum. If they are, heavy cream would be a better option. Also it matters how much. A tablespoon in five cups of coffee a day is quite different than a single teaspoon in one cup of coffee. Quantity matters.