Sunday, October 3, 2010

Vitamin D, Sunshine, and Great-Grandparents

Photo courtesy of Estrilda's photostream

Recently I had a long conversation with a friend about Vitamin D, and the increasing number of people who don't get enough of this very necessary vitamin. My friend is a gardener, and outside in the sun many hours each day. Her question was why did our great-grandparents get enough Vitamin D from the sun while we do not?

My thought at the moment had to do with the possibility of fine pollutants in the atmosphere blocking the particular UV wavelengths needed to strike out skin to make Vitamin D. However, that idea of why we get less Vitamin D than our ancestors kept nagging at me for about a week, until I finally had to dig into it.

The short answer is: our FOOD supply. Actually it's a bit more complex than just that, but once I understood what Vitamin D does in the body, and what makes it work, I became certain our ancestors ate the real foods that helped their skin make Vitamin D from sunshine.

The important beginning point to understand "D", is that it is a fat-soluble vitamin. The other fat-soluble vitamins are A, E, and K and they must ALL be present in order for any of them to work at their primary functions in our bodies. Secondly, consider the term "fat-soluble"... it means exactly what it says. Those vitamins all need FAT in order to get into solution so that our bodies can use them. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats).

What does Vitamin D do? Basically it is critical to bone health (by helping the body absorb use calcium) and immune system functions. Deficiencies have been linked to several major diseases like cancer, heart disease, high blood pressure and osteoporosis. I suspect it might also be linked to S.A.D. but I haven't seen any studies on it.

Healthy skin makes Vitamin D from sunshine. Notice I said "healthy skin"... IF our skin is not well-nourished by Vitamins A, E and K2, all the sunshine falling on the planet will not make Vitamin D in our skin. 

Vitamin D can be broken down into D2 and D3, which are the most common forms of Vitamin D although D2 is not a natural vitamin, and is not present in enough quantity to be detected in the human bloodstream. The Vitamin D added to pasteurized milk is D2, and recently has been linked to calcium mal-absorption. (D2 was patented and then licensed to pharmaceutical companies in the 1920's... and is manufactured by subjecting a plant fungus to ultraviolet light.)

Back to the other vitamin needs in order for Vitamin D to function properly... Vitamin A doesn't come from carrots! Carrots and other orange-colored vegetables only provide beta-carotene, which is just a pre-cursor to Vitamin A and is not very efficiently converted (est 10-12%) to retinol in the small intestine. Retinol is the animal form of Vitamin A, found in egg yolks, liver (even cod livers and chicken livers) and butter. Retinol becomes retinal in the human body, giving us good eyesight, skin health and bone growth. Since conversion of beta-carotene is so poor, the most reliable sources of Vitamin A are animal foods.

Vitamin E works synergistically with Vitamin D; recent research indicates E may act more like a hormone in the body rather than the antioxident is has been thought to be. There is a lot still unknown about Vitamin E in the human body, but we do know Vitamin D needs it to function. Unlike the other fat-soluble vitamins, sources of E are primarily plant-based foods like broccoli, spinach, seeds/nuts and their oils (like olive oil).

Vitamin K is generally less known than the other vitamins. Dr. Weston A. Price identified it many years ago as a compound he called “Activator X”. As with vitamins A and D, there are two main forms of vitamin K, known as K1 and K2. K1 is the predominant form of vitamin K in the diet, coming from plant foods (such as spinach, swiss chard, cabbage, kale, broccoli, avocado and kiwi). K2 consists of MK-4 and MK-7 forms, which are found only in animal foods (egg yolks, butter, beef, hard and soft cheese).

The primary function of K1 is for blood clotting, and K2 to convert a protein molecule to GLA, Gamma-linolenic acid. (GLA is one of the Omega-6 fatty acids.) Along with Omega-3 fatty acids, Omega-6 fatty acids play a crucial role in brain function as well as normal growth and development. Also known as polyunsaturated fatty acids (PUFAs), they help stimulate skin and hair growth, maintain bone health, regulate metabolism, and maintain the reproductive system.

Vitamin K2 is normally produced by the fermentation process of bacteria in the large intestine (if given the proper nutrients in our diet), and dietary deficiency is extremely rare unless the intestines are heavily damaged, unable to absorb the molecule, or are subject to decreased production by normal gut flora, from antibiotic use.

I have read this idea over and over, in many ways and many places, and I'll repeat it here: What's interesting is that the very foods required to give us these essential vitamins are the very foods we are encouraged to reduce or eliminate (dietary fats). I did a label-check while I was at the supermarket... several packaged foods listed the water-soluble vitamin content (like Vitamin C) but none listed any fat-soluble vitamins. The exception was Vitamins A and D added to fat-free milk. What's wrong with that picture?

So, if you want to increase your Vitamin D, increase your real animal food/fat intake. (BTW, it is not understood but somehow the natural, fat-soluble vitamins also work together to avoid any toxic accumulation among them.)


  1. Darius, I think you have made a valid point, but there is more to it than that. You and your friend are not typical Americans. The studies that show we have a vitamin D deficit usually add that the average American spends less than 20 minutes *per week* outside in the sunshine!! Most Americans these days go from building to car to building without spending any time at all in the great outdoors. To compound the problem, doctors have warned us to use sun screen whenever we do expose our skin to sunlight, and sun screen blocks vitamin D as well as the harmful rays. We have developed a sunphobia as a result. So, yes, healthy foods, vitamins and essential fatty acids -- but people do have get outside as well!

  2. Oh I agree completely! Most of us don't get outside enough, especially our elderly who need more Vitamin D than middle-aged adults.

    Hopefully, we'll know about this essential vitamin in the next few years. Just the fact that NIH is considering a review helps.

    I am (or was) a strawberry-blonde and lived with 'suncreen skin' for most of my life. Even with all my gardening and no sunscreen use for several years, I barely tan... and never burn anymore.

  3. Maybe that explains why cholesterol-lowering medication, on average, been shown to have significantly poorer sex life . Although vitamin D is a steroid hormone produced by cholesterol spring valley vitamins


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