Ever wonder why people tend to get sick in winter? There’s lot of theories, including that we spend more time indoors and close to others. Another reason is that the flu virus can live longer outside of a “host” in the colder, dryer winter air as proposed in a fascinating study here.
But there’s another reason I believe also completes this puzzle of why the flu only seems to come out in winter: Vitamin D deficiency makes us more susceptible to viral attack (along with zinc deficiency too).
Vitamin D is a steroid hormone (not really a vitamin) that our body creates when it is exposed to direct sunlight. It also comes from foods like pastured meats and eggs, liver, wild fish, sardines, and oysters. Most of us are already low or deficient in Vitamin D because unlike our ancestors who lived outdoors, we live inside offices and Starbucks, and because few of us are eating the foods listed above. About 80% of my clients come into my office with Vitamin D levels in the “deficient” range (see chart below).
Those of us in the northern hemisphere above the 35th parallel likely produce little Vitamin D in our body between October and March. I have not yet found a way to invent a computer screen that emits vitamin D creating light (but if you steal my idea, I expect half the profits – honor system here, folks). The vitamin D theory of the winter illnesses holds some water as evidenced by research here, here, and perhaps most forcefully in a 2009 study published in JAMA here.
Of course the Naysayers have some studies suggesting Vitamin D has no effect on your ability to fight the flu. After reviewing such research, it appears these studies only looked at the dosing, not the participants’ actual levels. You could give someone all the Vitamin D in the world, but if it’s not raising their blood levels within an optimal range, the study is not reliable.
So what is an optimal level of Vitamin D?
No one knows and researchers are in a hot debate on this right now. There are basically two camps: the 35-50ers and the 50-70ers. And then there’s the Philadelphia 76ers, but no one likes them and they don’t have anything to do with this discussion anyway.
I’m in the camp of the 50-70ers, with one exception: that level should be achieved at least in part through sunlight and food over supplementation. I know people who take mega-doses of refined vitamin D supplements for long periods of time to get that level, which I don’t recommend. And there is some evidence that those dealing with very serious illnesses can benefit from extra high, therapeutic levels.
I base this opinion in part on studies that look at the levels of those modern hunter-gatherers and societies who live outdoors most of the time – like we did more than 10,000 years ago. Studying people in traditional cultures that are relatively free from “western” diseases is often a good way to know what may be optimal for the rest of us.
A study last year of the Masai people showed their average levels at 48ng/ml (range: 23-67). And the Hadzabe averaged 44ng/ml (range: 24-68). My recommendations in the attached graphic are based in part on this study:
In winter (October – March) I personally take 4,000-6,000 IUs of D3 (cholecalciferol) from a supplement and a teaspoon of Green Pasture Fermented Cod Liver Oil / Butter Oil Blend or a tablespoon of Carlson Cod Liver Oil (containing about 1200 IUs of D3) for a total of 5,200-7,200 IUs per day. In summer, I cut back my supplement to 2,000-4,000 IUs per day and stay on the Cod Liver Oil or Green Pasture Fermented Cod Liver Oil (Have no idea what that is? Learn about it here).
Listen to your body and your chosen team of health clinicians to guide you for the levels that may be right for you. I have had patients who just felt terrible with levels above 50ng/ml before seeing me (possibly because of other deficiencies – see the end of this post) and others who did not get better until they surpassed that. I think the best evidence today suggests that anywhere from 35-70ng/ml would be a widely safe for most adults.
These are just what I need to keep my levels around 55-60 ng/ml. You may need drastically different amounts. It’s always best to get tested which is usually covered by insurance, or you can order your own test kits online.
The best ways to increase your vitamin D:
• SUMMER: Exposing your skin to direct sunlight (not through windows). The rule of thumb is 15-20 minutes of sunlight on 70% of your body between about Noon-4pm or when your shadow is shorter than you are.
• WINTER: If you live above about the 35th Parallel (Washington DC near where I live is at the 38th), you are probably not making any Vitamin D between October and March no matter how much sun you get.
• Cod Liver Oil (I only recommend Carlson and Green Pasture – avoid most others).
• Wild seafood, especially fatty fish, caviar, and oysters. I prefer VitalChoice.
• Eat mushrooms that have been grown or dried in sunlight. See here.
• Vitamin D Supplements (my favorites are Carlson A&D from Cod Liver Oil and Enzymatic Therapy Chocolate Chewables, available here).
A Word About Vitamin D Supplements
It’s important to know that Vitamin D is a family of similar hormones. When you take a pill form of Vitamin D, you are often getting just one isolated form. No supplement will ever fully replace the value of getting your Vitamin D from direct exposure to the sun and from Vitamin-D rich foods.
The Vitamin A-D-K2 Connection
The fat soluble vitamins (A, D, E, and K2) are fascinating, and they work synergistically together. It’s another reason I recommend getting your Vitamin D from food because Vitamin D greatly increases your need for Vitamin A (retinol) and K2, as Chris Masterjohn, PhD has clearly outlined here.
The bottom line is that we now know that getting Vitamin D along with pre-formed Vitamin A and Vitamin K2 in balance is important. Thankfully, if you take a high quality fermented cod liver oil (with a high vitamin butter oil blend) from Green Pasture, you get these in a natural balance. Yet another reason to not rely solely on a refined supplement.