I’m not in the business of ranking vitamins, but if I was, I’d probably put Vitamin D right at the top of the list. It’s right at the heart of a healthy immune system–among other things–and most of us are deficient.

If you are below 50ng/ml, you are deficient. It’s suspected that about 70 percent of Americans are Vitamin D deficient. Above 50ng/ml is good–it allows you to avoid a complete immune breakdown, but by getting those levels up to 100, you are putting yourself in a position to avoid all sorts of diseases, from cancer to heart disease to lupus to Crohn’s to even the common cold.

But if it is lower than 50ng/ml, not only are you putting yourself at risk for disease, you get all of these unpleasant side effects. For example:

• Sore muscles and bones – without Vitamin D, your bones cannot mineralize non-organic substances, namely calcium, meaning it cannot integrate anything not carbon-based into itself.
• Depression and moodiness – While we’re not entirely sure why, Vitamin D deficiency and depression are very clearly linked with low Vitamin D levels associated with more than 1,000% greater chance for that person suffering from depression. It also lowers serotonin levels in the brain, which can lead to being in a bad mood.
• Gum disease and poor oral health – Without Vitamin D, the healthy bacteria in your mouth die and this leads to gum disease and other dental issues.
• High blood pressure – Does low Vitamin D cause high blood pressure? Does high blood pressure cause Vitamin D deficiency? Does a lifestyle that leads to high blood pressure also lead to low Vitamin D? Hard to say, but the two go hand in hand.
• Hair loss – Vitamin D is required in the body’s creation of keratinocytes, a compound used to develop epithelial cells in the skin that promote hair growth. For more information, see this article.
• Chronic fatigue – Without Vitamin D, you get tired. Simple as that.
• Weight issues/obesity – You fat cells remove Vitamin D from your system. It doesn’t matter how much Vitamin D you put into your body–be it from supplements, food or sunlight–enough fat will take it out of your system before it can do you any good.
• Allergies –  This one isn’t very cut-and-dry. It could be or could not be Vitamin D related. But being low in Vitamin D has been shown to lead to an increased sensitivity to allergens.

What are the long-term risks of deficiency?

The issues listed above are damaging, to be sure, but none of them are life-threatening all by themselves. But long-term Vitamin D deficiency can become life-threatening at some point if it isn’t taken care of. These diseases are linked to long-term Vitamin D deficiency:

• Osteoporosis
• 17 of the most common cancers (colon cancer, breast cancer, prostate cancer for example)
• Alzheimer’s disease
• Gout
• Multiple Sclerosis
• Heart disease
• Parkinson’s disease
• Autoimmune diseases (which include everything from arthritis to lupus to diabetes)
• Bursitis
• Depression

How do I keep my levels up?

The easiest and most effective way to get Vitamin D is to spend time in the sunlight. 30 minutes a day of full sunlight will get you enough Vitamin D to keep your levels up high. However, the strength of the sun diminishes during the winter months and it is harder to get enough Vitamin D for half the year.

That’s why supplementation is necessary. But you must get quality supplements or you’re wasting your money and putting hope into something that won’t actually help you. Two very reliable supplement companies are Maximized Living and Systemic Formulas. These are the companies I use in my office.

Beyond that, Vitamin D comes from protein. Eat grass-fed beef, free-range chicken and eggs and wild-caught fish. You’ll be ingesting large amounts of Vitamin D when you eat good protein. The absolute best food source for Vitamin D is, unfortunately, something not many people enjoy: beef liver. If you like it (hello Germans out there), don’t be shy. Eat as much as you can.

If there are any vegetarians out there, getting Vitamin D from fruits and vegetables is more challenging but can be done via Almonds and mushrooms, particularly maitake, portabella and chanterelle mushrooms. In the case of vegetarians, extra sunshine and supplementation is recommended.

As winter sets in (even here in North Carolina), I urge you to take your Vitamin D levels more seriously. This is the most challenging time of year for our immune systems, and this alone will give you a powerful defense.

Dr. Aaron Ernst, D.C. is host of News Talk 1110 WBT’s “AskDrErnst” show and clinic director of Maximized Living Charlotte.

He specializes in providing customized nutritional and detoxification total body healing programs, utilizing the 5 Essentials of Maximized Living.