Elizabeth Somer is a registered dietitian who has written nine books about what we eat and how it makes us feel. Her latest book is Eat Your Way to Happiness. Here, she discusses which foods do the best job of making us feel happier.

Q: Which foods make us happiest?

A: First, let me say that it is a style of eating, not just a few foods, that will stack the deck in favor of feeling great. You can't toss a few blueberries into an otherwise junk diet and think you will boost your mood!

I outline the 10 secrets of happy, skinny people in the book, which include eating the 1,2,3 breakfast, focusing on "real foods," cutting back on the quick fixes such as sugar, and keeping both lunch and dinner light. If you are following those guidelines, then sprinkling that eating plan with a few super mood foods ( I mention 12 in the book, along with a few of the following) can give you an even greater bang for your buck.

3 happy foods after the jump

1. Salmon: For years, nutrition experts focused on the exciting connection between the omega-3 fats and heart disease. Then a few researchers started to wonder about the effects the omega-3s might have on the brain. Study after study has now shown that people who are depressed have much lower omega-3 DHA levels in their blood, fat tissues, and cerebrospinal fluids - up to 36% lower than happy people. In fact, as DHA levels drop, so do levels of the feel-good brain chemical, serotonin, leaving people grumpy, blue, and down-right depressed. If your DHA levels are low, you have 2.6 times greater risk of getting really crabby and blue compared to someone who keeps those levels high.

On the other hand, boost intake of DHA by including more DHA-rich foods or by taking supplements, and serotonin levels rise and mood improves. Studies show up to a 50% reduction in depression in people who are the toughest to treat and even an improvement in well-being for those battling every-day blues. The evidence is so overwhelming that the American Psychiatric Association in 2006 recommended omega-3s be included in any treatment for depression.

You can get all the omega-3 fat you want from flaxseed, walnuts, canola oil, leafy greens, or soy to help lower your risk for heart disease, but those foods will do nothing for your mood or memory. That's because there are three omega-3 fats, and they are not all created equal. It is only the omega-3s in fish, especially DHA, that will boost your mood. Aim for two servings of omega-3-rich fish, such as salmon, every week, choose foods fortified with DHA, and/or take a daily supplement that contains at least 220 milligrams of DHA.

2. Whole grains: By quality carbs, I mean 100% whole grains or starchy vegetables, such as sweet potatoes. These are the foods that help boost the feel-good brain chemical, serotonin. When serotonin levels are high, you are happier, sleep better, and are calmer and more at peace with your life. While refined grains and sugar wreak havoc with blood sugar levels and can undermine mood, your brain thrives on quality carbs. If you find yourself craving a carb-rich snack mid-day, it could be your brain telling you it needs more serotonin. Rather than turn to the sugary junk or the refined and processed grains, have a whole wheat English muffin with some jam or a small bowl of air-popped popcorn to boost serotonin levels. These snacks also make great bedtime munchies to help you sleep better at night.

3. Berries: Lots of processed foods at the grocery store - from exotic juices to designer yogurts - will try to convince you they are packed with more than their share of nutrients or antioxidants. Most are more hype then help. What truly makes a food super? There are three requirements that I outline in the book, with one being that it must be packed with antioxidants.

Free radicals are little oxygen fragments inhaled in air pollution and tobacco smoke, consumed in fatty foods, and generated in the body during normal metabolic processes. Left unchecked, these oxygen fragments or oxidants, attack cell membranes and the genetic code - a process called oxidation. Like the bumper on a car, your body "rusts" when exposed to oxygen, which causes cells to either die or mutate. Cell "rusting" or oxidation contributes to all age-related diseases, from heart disease andcancer to depression, memory loss, and possibly even dementia and Alzheimer's.

The good news is: your body has an anti-free radical system, called the antioxidants, that prevents oxidants from damaging brain cells. Stockpiling antioxidants is essential throughout life, especially when we are stressed and as we age. These antioxidants are in the colour or pigment of fruits, vegetables, legumes, whole grains, and other real foods. The more color, the more antioxidants. That's why a fruit as richly-colored as berries is so antioxidant packed and has been shown to reduce depression and memory loss. Add them to smoothies, pile on top of cereal, toss into salads, eat frozen as a replacement for ice cream. Better yet, combine them with a little dark chocolate, which I discuss in the book also helps protect brain cells. Dunking strawberries in chocolate syrup - now, if that doesn't make you happy, nothing will!!