According to MYPlate.gov and the USDA, we should be consuming at least half of our grains from whole grains.
White and refined/processed grains, become an issue if you aren't making those choices to incorporate half your grains with whole grains. Which, let's be real, most Americans are not. Eating too many refined carbohydrates/white products, especially in the form of white flour, cookies, breads, pasta, cereals, etc. has been associated with increased risk for obesity, diabetes, heart disease and many other diseases and cancers. Making sure at least half your grains are whole grain, can be a fairly simple switch. Think: whole wheat pasta, brown rice, quinoa, whole wheat bread, etc. Little changes make a big difference.
What's the difference between white grains and whole grains? 100% whole wheat/whole grain products contain contain the entire grain kernel ― the bran, germ, and endosperm. Whole grains also contain dietary fiber (important for bowel function and for providing a feeling of "fullness"), as well as vitamins and minerals - including several B vitamins (thiamin, riboflavin, niacin, and folate),and iron and magnesium. All of these nutrients above play vital roles in the body including helping the body release energy from the foods we eat (B vitamins), helps the body form RBC's (folate), carrying oxygen in the blood (iron) and aid in building bones (magnesium). Refined grains on the other hand, have been milled, which is a process that removes the bran and germ. But it also removes those key nutrients - dietary fiber, iron, and many B vitamins. You can find grains that have been enriched, like "enriched white bread" - this means that (only) certain B vitamins and iron have been added back after processing. BUT - dietary fiber is not added back.
The best time to eat refined/white grains is pre or post workout. For general fitness and resistance and weight training, it's important to eat a pre/post workout meal that is low in fiber to ensure your muscles receive the fuel from your food as quickly as possible!As we've learned, whole grains contain vitamins, minerals and dietary fiber. Dietary fiber helps slows down the digestion and absorption of the foods we eat, which also helps stabilize our blood sugar levels as well. White products however, lack the fiber (and nutrients). Due to the lack of fiber content, a plain, white bagel (for example) is optimal to consume as a pre or post workout carbohydrate.