"In a lot of cases, yellow or dark teeth tend to hold people back," says Levine. The less you smile, the more you miss out on opportunities to exude approval, power, friendship, attraction and even a positive outlook on life. "Smiling increases the production of serotonin [and] has been scientifically proven to elevate the mood of both the person giving the [smile] and the person receiving it," Levine explains. With a whiter and brighter smile, you're prone to smile more often and project more confidence. The end result? Way more self-esteem, no self-help books or motivational speakers required.

The confidence that comes with a brighter smile not only positively affects your personal life, it boosts your professional life as well. Numerous studies show that a bright smile, the key to a great first impression, has a direct effect on successful interpersonal interactions in a professional setting. In mock job interviews, prospective employers viewed candidates with whiter teeth as more professional, open, trustworthy and healthy. Not only were employers more likely to hire candidates with bright smiles, they were also more likely to offer them higher salaries.

It's easy to whiten teeth in minutes with at-home products, and you can maintain that bright smile by stocking your kitchen with the right ingredients. "Nutrition is critical," says Levine. "Eat healthy, green, leafy vegetables and fruits that raise the pH of the mouth, allowing good types of bacteria to thrive." Also look for crunchy vegetables like celery and carrots, which naturally remove surface stains. Here are the top items Lowenberg recommends adding to your grocery list:

Kale: The consistency is so dense and rough that it cleans your teeth as you are eating it, removing surface stains.

Cheese: One of the best and easiest ways to combat acid erosion in your teeth is to eat a piece of cheese after every meal. Cheese is rich in protein, calcium and phosphorus, all of which can help buffer the acids in your mouth. Cheddar is best, since it contains the highest levels of alkali; soft cheeses like brie or feta won't have much of an effect.

Strawberries Strawberries are a great, natural way to whiten teeth. You can just eat them or brush your teeth with a paste of strawberries and baking soda. Be sure to thoroughly clean teeth afterward to prevent tooth decay.

Apple Cider Vinegar: Mix apple cider vinegar with baking soda to make a natural toothpaste, or gargle with it daily before brushing to help remove surface stains.

Oranges: Buff teeth with the inside of the peel or combine ground bay leaves and dried orange peel to create a toothpaste that leaves a brilliant shine.

Bananas: Next time you're about to throw out a banana peel, rub it on your teeth for two minutes. After 15 minutes, brush your teeth with your regular toothpaste. Repeat this process two to three times a week.

Levine urges the importance of a great home care routine. That means teaching yourself to clock in a full two minutes (no cheating!) of brushing twice a day and flossing once a day. "If the plaque is cleaned off the teeth effectively, foods and liquids will not stick to them and thus [create fewer] external stains," Levine explains.

If your coffee or red wine habits start to dull those pearly whites, it's safe to maintain your smile with once-a-month whitening sessions.