Are you in a bad mood? Feeling sluggish? Having trouble focusing? Your diet could be at fault.Dr. Connie Guttersen, R.D., Ph.D., and New York Times bestselling author of The Sonoma Diet, shared her insights with SheKnows.com to help us better understand how to eat for optimum energy and mood.She recently updated her bestseller with new health information, further tips for making healthy eating enjoyable, more recipes (including more gluten-free options) and additional discoveries about the importance of low glycemic meals when it comes to boosting energy levels.The food and mood connectionDifferent foods and their particular nutrients can have an effect on how our brain processes signals related to mood, hunger, sleep and stress, Dr. Guttersen explains. What we eat (or don't eat) can make a huge difference when it comes to how we feel, both short term and over time. For example:* Depression is linked to a lack of B vitamins, such as B6, folic acid, and B12. * Depleted amounts of magnesium, calcium, zinc, and selenium can contribute to mood disorders. * We need B vitamins to effectively convert calories into energy for the cells. * Carbohydrates, especially whole grains rich in B vitamins, promote the production of feel-good hormones such as serotonin. * Calcium helps to counteract lactic acids produced by tense muscles, which often feels like an aching, tired sensation in the body.Hydrate to feel greatA whopping 75 percent of the human body is made up of water, which means in order to maintain both energy and mood you need to stay hydrated."Even if you are not feeling thirsty, drink up," Dr. Guttersen says.Feeling tired and lethargic can be a sign of dehydration, but if you start drinking more water consistently you'll become better attuned to the needs of your body and not let yourself get to the point of wanting to nap just because you've skimped on drinking water.Keep a reusable water bottle with you all the time, and within reach so you can be constantly sipping. Water not only keeps you hydrated, it transports food and oxygen to different cells, controls blood pressure and electrolyte levels, helps the kidneys flush out toxic substances and helps regulate our body temperature. We'll drink to that!Balance your blood sugar with low-glycemic foodsKeeping blood sugar levels in a healthy range is very important for maintaining consistent energy levels and preventing mood swings, says Dr. Guttersen.The best way to do this is to consider the glycemic index (GI) when making food choices, then opting for low-GI foods, or those that won't cause spikes and dips in your blood sugar level.Foods further down the GI (lower than 55) are metabolized more slowly, keeping your appetite on a more even keel.This means that low-glycemic foods are better at providing a slow energy release throughout the day, rather than giving you a short burst of energy, then leaving you feeling tired and sluggish (and cranky) soon after.Source; Sheknows.com