hi Fumih,
Chromium is best taken on an empty stomach, since food will interfere with its absorption. That's the only reason the directions say to take before a meal
Chromium does not blast into the bloodstream and make the blood sugar go down when you eat a meal afterwards, although I've seen ads for supplements that imply that's how it works. Depending on the dose, chromium can be taken once a day, or in divided doses. Over the course of the day, the body uses chromium to make "glucose tolerance factor" (GTF) which is found in the cell walls. This GTF appears to help insulin to be more efficient at getting glucose out of the bloodstream and into the cell. Studies suggest chromium helps with insulin resistance. For people with diabetes, it can make anti-diabetic drugs more efficient, so you need to have your doctor to monitor closely, since you may require a reduction in your meds to prevent serious hypoglycemia.
Improving the efficiency of insulin means there are fewer big dips and swings in blood sugar. This is how chromium can help with cravings.
Eating a high-carb, sugary white processed diet can make us deficient in chromium ... not just because we don't eat enough foods that contain it naturally, but because such a diet will deplete what we do have very quickly. Foods rich in natural chromium include brewer's yeast (but not torula or other nutritional yeast), liver, dried beans, meats and dairy, also some seaweeds.
For general maintenance, the dose is 200 µg (micrograms) per day ... To treat deficiency, the dose is 400 µg per day (as a single dose or divided into 2 doses). For blood sugar disorders, such as diabetes or hypoglycemia, the dose is 400 to 1000 µg per day in 2 - 3 divided doses .. Using doses over 500 µg per day should be monitored by a health care professional, and definitely if you have a diagnosed condition .. as noted above, it can affect medications that you may also be taking. Using more than 1,000 µg per day can lead to toxicity, which inludes kidney and liver problems, and heart rhythm disturbance.
hth,
Doreen