Vitamin D has been getting more attention in the last 2 decades, but really, it’s still not getting enough. Often referred to and remembered as the sunshine vitamin, we don’t have to dig very deep to understand why we have become mostly deficient. Sunscreen and chronic “indoor-itis” are two of the main reasons.
Think this micronutrient is just about strong bones? Nope. Vitamin D stands alone as a vitamin and a hormone, “playing a pivotal role in cell metabolism, cardiac health, immune function, neurological support, and the regulation of systemic inflammation—a process central to the onset of many chronic diseases. Unlike other vitamins, vitamin D can be synthesized by humans and is therefore not truly a vitamin (a vital food substance), except in those individuals lacking sufficient exposure to strong sunlight.” 
So when we ask, “what foods are high in vitamin D?” the answer is none, really (except that tasty cod liver oil actually!). “Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks.”  Then you can start to get into more processed foods like fortified cereals, some brands of orange juice, yogurt, margarine (#notrealfood) and a few others.
Needless to say you simply can’t eat enough of those foods, especially every single day to get optimal levels of this superstar—and we want to be high in vitamin D! The best approach? Get outside more (way, way more!), and supplement on the days where you don’t or there isn’t strong sunlight. Optimal vitamin D intakes are at least 1000-2000IU per day; 2000-4000IU if you’re pregnant; 4000-6000IU if you’re breastfeeding. RDAs are just a starting point; those guidelines were developed to prevent deficiencies a long, long time ago. We’re past that bare minimum recommendation; we want to live long, healthy, vibrant lives right? Right!
I can’t emphasize enough how important vitamin D is to your overall health. Do some more research and you’ll be astounded at what the newest findings are. “Excess vitamin D is stored in cellular tissues, to be activated at any time in order to regulate aberrant cell growth that can lead to cancer…inducing apoptosis, or cellular suicide…effectively snuffing out cancer before it takes hold.” If that wasn’t enough, find out more about its effects on heart disease and immune support!
It’s always a great idea to go and get your levels tested too, especially if you live in a warmer climate. Supplementation should always be looked at on an individual basis; there is no one-size fits all. Depending on where you live, you may have to pay for the test, but it is well worth every penny. When choosing a supplement, look for it in the right form. Research suggests Cholecalciferol (vitamin D3) is better than competing forms at raising levels of vitamin D in the blood; this is the form you get from sunlight. Look for at least 1000IU per tablet or serving. I supplement with this all year long now, unless I’m outside for at least 30 minutes and the sun is bright, with no sunscreen and most of my body exposed (wearing too much clothing takes away from the effect). Just don’t burn yourself!