Most of us know two things about vitamin D: It's the "sunshine vitamin" and it's needed in order for our bodies to absorb calcium to build strong bones. You were probably told growing up to spend time outdoors and drink more milk in order to get enough vitamin D, which is great, but unfortunately there are still a lot of people who suffer from a vitamin D deficiency and most aren't aware of it.
This vitamin is the only nutrient that your body produces when exposed to sunlight and is responsible for helping you build strong bones, but there is so much more to it than just that! Vitamin D is actually a hormone and not having enough of it can have a few negative health effects that you want to avoid. If you're wondering to yourself right now whether you might be lacking in vitamin D, then continue reading because I'll be covering why having enough of this nutrient is important, risk factors of vitamin D deficiency, and the best food sources to get it from. Let's get started!
Why is vitamin D important?
Vitamin D is a fat-soluble vitamin, this just means that it dissolves in fats and oils and can be stored in your body for long periods of time. Aside from being a vitamin, it also functions as a steroid hormone. This is because vitamin D is naturally produced by sunlight and when your skin is exposed to the sun our bodies produce this steroid hormone from it. In fact, every single cell in our body has a receptor for it that affects many different body processes. This is what makes vitamin D so important and why we need to make sure we get a sufficient amount of it.
Here are the four main health benefits vitamin D has:
1. Helps to keep your immune system strong enough to fight off illnesses.
Vitamin D has anti-inflammatory and immunoregulatory properties which are responsible for the activation of immune system defences. It also is known to enhance the function of immune cells that protect your body against harmful bacteria.
So getting enough of this vitamin is crucial to have a functioning immune response. In fact, low levels of vitamin D are associated with an increased susceptibility to infection, disease, and immune-related disorders. 
2. Important for normal growth and development of bones.
Vitamin D helps the body absorb calcium so that the blood calcium levels are at the ideal point to enable mineralization of bone in order to keep them strong and healthy. In fact, being deficient in vitamin D can lead to osteomalacia which results in poor bone density and muscle weakness and can lead to even more health complications at an older age like osteoporosis.
3. Provides mood support.
Remember that we have several vitamin D receptors throughout our bodies, and some happen to be in areas of the brain that are responsible for mood and behavior. Which may be the reason why low vitamin D levels can affect symptoms of depression or other mood disorders.  Vitamin D has actually been linked to easing symptoms of clinical depression. One particular study found that people with depression who supplemented with vitamin D noticed an improvement in their symptoms. 
However, it's important to note that this doesn't mean that taking a vitamin D supplement is a sufficient stand-alone treatment for depression.
4. Boosts weight loss.
Higher vitamin D levels has also been linked to weight loss. In this particular study, a group of overweight and obese women were observed for over the course of an year. All women were put on a calorie restrictive diet and exercises routine, and half of the women had to take a vitamin D supplement, the other half took a placebo. At the end, researchers found that women who met their daily vitamin D requirements experienced more weight loss than the women who did not.  Although weight loss can happen for a number of reasons, they say that vitamin D can have appetite-suppressing effects due to it increasing levels of serotonin.
With all these health benefits it offers, you might be wondering... How much vitamin D does one actually need? Well, it depends on your age..
- Birth to 12 months: 400 IU
- Children 1-13 years: 600 IU
- Teens 14-18 years: 600 IU
- Adults 19-70 years: 600 IU
- Adults 71 years and older: 800 IU
- Pregnant and breastfeeding women: 600 IU
You can also consult with your doctor or dietitian to see what is the right amount of vitamin D for you.
Vitamin D deficiency
As you can see, vitamin D is needed to keep your body functioning well. Getting enough of it is needed to help protect against several health conditions like heart disease, infections and immune system disorders, and poor bone and joint density.
But how does a deficiency in this vitamin happen if our bodies can create it? It could be for a number of reasons, here are the three most common risk factors:
- Skin type: Having dark skin reduces the body's ability to absorb UVB rays from the sun.
- Sunscreen: Sunscreen with SPF of 30 or greater can reduce the body's ability to synthesize the vitamin.
- Geographical location: Living far from the equator, or in northern latitudes, where there is little sun year-round. Also areas with high air pollution.
A few other factors include, not eating enough fatty fish or dairy, being elderly, being overweight or obese, and staying indoors most of the time. All of these can lead to a number of health problems that vitamin D helps protect against.
Signs that might point to a deficiency in vitamin D:
- Getting sick often
- Bone and back pain
- Muscle pain
- Depression or other mood disorders
- Slow healing of wounds
- Hair loss
Keep in mind that these can be signs of other health issues, so please consult with your healthcare provider if you think you have or are concerned about having a vitamin D deficiency.
How to get enough vitamin D
There are three main ways to get vitamin D, they include:
- Sun exposure. You should aim to get about 15-20 minutes of sun three days per week, with no sunscreen. Apply it after 15 minutes if you plan to be out for a longer period of time.
- The foods you eat.
- Nutritional supplements.
The absolute best source for vitamin D is sunlight so your first priority should be getting enough sunlight! Your second should be food, and your very last resort should be consulting with your doctor in regards to taking a vitamin D supplement.
With that being said, if you live in an area where there is little sun then try to incorporate foods rich in vitamin D into your diet! There are two types of vitamin D found in natural food sources: vitamin D3 (mostly in animal and dairy products) and vitamin D2 (mostly plant products).
Here are some of the best food sources that are high in vitamin D2 and D3:
- Salmon: Wild salmon contains about 988 IU of vitamin D per serving and farmed salmon contains 250 IU, on average.
- Canned tuna: 3 oz of canned tuna in water contains an average of 154 IU of vitamin D.
- Herring and sardines: 100g of herring can contain up to 216 IU and one can of sardines (3.8 oz) can contain up to 177 IU.
- Cod liver oil: One tablespoon has approx. has 1,360 IU.
- Egg yolks: A typical egg yolk contains 37 IU.
- Mushrooms: Wild mushrooms that are exposed to UV light, like Portabella or raw white mushrooms (per 50g) can contain up to 568 IU. 50 grams of dried shiitake mushrooms can contain up to 77 IU and raw maitake mushrooms can contain up to 562 IU.
- Fortified foods: This includes cow's milk, soy milk, orange juice, and some breakfast cereals. These typically contain 54–136 IU per serving.
The bottomline is vitamin D deficiencies are quite common and often overlooked. But your body needs this fat-soluble vitamin in order to support a strong immune system, promote good bone health, help with mood support, and even help with weight loss! So remember, make sure you're getting enough sun and eating natural food sources like fatty fish, dairy products, mushrooms, and fortified foods!