The shorter days of winter have many of us coming and going in the dark. And that means we're likely getting much less vitamin D from the sun than we did in the summer. Studies have shown that low levels of vitamin D can affect mood — and possibly even aggravate the seasonal depression that affects so many in the winter in the form of seasonal affective disorder. So it's important to take stock of your vitamin D levels to ensure you're getting enough.

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Before you reach for that bottle of supplements, take a closer look at the foods you probably already have in your kitchen that are naturally high in vitamin D. Here are nine excellent sources of the sunshine vitamin:

1. Oily fish

Fatty fishes such as salmon, trout, tuna, mackerel and eel provide anywhere from 400 (mackerel) to 580 (smoked salmon) international units (IUs) of vitamin D. That's a big chunk of the recommended 600 IUs that you should be aiming for each day (800 IUs if you are over 70.)

2. Canned fish

bowl of Canned tuna high in vitamin DCanned tuna and sardines are inexpensive sources of the sunshine vitamin. (Photo: HandmadePictures/Shutterstock)

If fresh fish isn't available, check out your store's supply of canned fish such as tuna or sardines. These inexpensive options still provide between 180-250 IUs of vitamin D, and they can be a lot easier to find and afford than fresh sources.

3. Portobello mushrooms

mushrooms on a chopping block - mushroom are high in vitamin dLooking for a vegetarian source of vitamin D? Try mushrooms. (Photo: misszin/Shutterstock)

These hearty mushrooms, along with morels, oyster mushrooms and chanterelles, are excellent vegan sources of vitamin D. Portobellos have about 375 IUs per serving, so go ahead and add some to your salads, soups and sandwiches.

4. Milk

cup of milk on a table high in vitamin dWant to fight off the winter blues? Add one cup of milk to your day for a healthy dose of vitamin D. (Photo: Sea Wave/Shutterstock)

Most brands of milk are fortified with vitamin D. Depending upon the brand, a glass of milk usually provides around 100 IUs but check the label to make sure. Also, many dairy products made with milk — like yogurt — may contain vitamin D but ice cream and most cheeses often do not.

5. Orange Juice

carafe of orange juice and a glass of orange juice high in vitamin dCheck the label to make sure that your OJ is fortified with vitamin D. (Photo: Sofiaworld/Shutterstock)

Like milk, many brands of orange juice are fortified with vitamin D — but the amounts may vary. So check the label if you're looking for a sunshine vitamin boost. Most brands that are fortified contain about 100 IUs.

6. Egg yolk

egg yolk which is a good source of vitamin dDon't skimp on the yolk if you want to boost your vitamin D. (Photo: 2creative/Shutterstock)

Egg yolks often get a bad rap, but they are chock full of vitamins and minerals — including vitamin D. So don't just toss them aside. One egg — complete with yolk — will give you about 40 IUs of vitamin D. Eggs will also provide you with potassium, protein, vitamin A, vitamin B-12, vitamin B-6, calcium and iron.

7. Certain cereals

cereal with berries using milk high in vitamin dAdd milk or soy milk to your cereal for a double shot of vitamin D. (Photo: Nika Art/Shutterstock)

It's no surprise that the cereals found on store shelves are vastly different when it comes to nutrients. So you'll need to do some serious detective work to find a brand that's low in the bad stuff (sugar and artificial colors), but high in the good stuff, like vitamin D.

8. Soy milk

glass of soy milk is high in vitamin dCan't tolerate dairy? Get your vitamin D from a tall glass of soy milk. (Photo: HandmadePictures/Shutterstock)

Fortified soy milk may offer a good dose of vitamin D, but as with all fortified products, the amounts may vary from one brand to the next. Check the label and look for one with 100-350 IUs of vitamin D per serving.

9. Tofu

cubes of tofu that are high in vitamin dJust one serving of tofu provides 20 percent of the recommended vitamin D you need each day. (Photo: Brent Hofacker/Shutterstock)

If you think it's just for vegetarians, think again. Tofu is an healthy source of protein, calcium, iron and — you guessed it — vitamin D. Add soft tofu to smoothies or creamy sauces, or try firm tofu in place of meat or chicken in stir-frys, curries, stews and sauces.