3 Things Everyone Should Know About Vitamin D

1. Vitamin D is inextricably linked to your overall health.

“Low vitamin D status is linked to a number of different conditions. These include certain cancers, muscle weakness and types I and II diabetes—possibly even schizophrenia and multiple sclerosis,” says Professor James Fleet, of Purdue University.

Vitamin D isn’t just about strong bones

It plays a role in cardiovascular disease, estrogen excess, brain cell growth and the inflammatory immune response.

Vitamin D Benefits

Vitamin D can affect the risk of breast, colon and ovarian cancers, possibly due to its role in the cell life cycle or its ability to block excess estrogen.

Various studies have found lower incidence of childhood asthma and Type I diabetes in children that live closer to the equator. These children have higher levels of sun-synthesized vitamin D.

A Framingham Heart Study found that low vitamin D in those over 59 years old contributed to two times the risk of experiencing a cardiological event (heart attack, heart failure or stroke) in the following 5 years of life.

Our immune cells contain receptors for vitamin D. Vitamin D seems to prevents prolonged or excessive inflammatory response which is linked to many autoimmune disorders: multiple sclerosis, rheumatoid arthritis, irritable bowel disorders, hypertension and psoriasis.

2. Vitamin D isn’t actually a vitamin.

What we know as vitamin D is really a precursor to a steroid hormone: it is also known as provitamin D.

The conversion of vitamin D happens first in the liver and then in the kidneys before it becomes the compound that is biologically active: calcitriol.

Vitamin D’s major role is the metabolism and maintenance of calcium. Calcium levels rise with added vitamin D supplementation and rising calcium may shut off vitamin D.

Increased calcium can cause mental confusion, heart rhythm problems and kidney stones. Calcitriol works with the parathyroid hormone to maintain calcium levels.

When vitamin D levels are low, the parathyroid becomes overactive. Hyperparathyroidism results in drops in phosphorous. Without phosphorous, calcium and other compounds cannot mineralize in bone. Therefore, vitamin D is also responsible for maintaining phosphorous levels in the blood.

Since vitamin D affects the ability of calcium to bind to proteins, it is believed that it is also linked to vitamin K (which has a lot to do with these proteins as well.)

Iron deficiency may slow vitamin D absorption and potassium may help conserve calcium in the body, thereby influencing vitamin D.

3. Milk is NOT your best source of Vitamin D

The dairy industry would have us think that milk is our best source of vitamin D. In fact,pasteurized milk is linked to both calcium and vitamin D deficiency disorders.

The best source of vitamin D is sunlight. Ultraviolet rays convert vitamin D into the form that our bodies use, and unlike food and supplement sources, it is very difficult to get too much vitamin D this way.

Your skin is able to regulate this vitamin D conversion according to heat and other factors, store pre-vitamin D for future use and destroy amounts above and beyond what is safe.

As little as 5 minutes of natural sunlight can cause vitamin D production in the body and 20 minutes produces 20,000 international units (IU).

It’s very difficult for those who live in northern latitudes to produce adequate vitamin D during winter months.

Tanning beds that emit 2-6% UVB radiation may help but research needs to be done on this.

Few foods naturally contain bioavailable sources of vitamin D. Fish is one of the best sources. A decade or so ago, the USDA listed the vitamin D content of dietary foods, but little research had been done at that time and analysis methods are still lacking.

Food Food Amount Vitamin D
IU (International Units) /
% Recommended Daily Value
Cod Liver Oil 1 Tablespoon 1,360/340
Salmon 3.5 Ounces 400/100
Mackerel 3.5 Ounces 345/86
Sardines 1.75 Ounces 250/63
Tuna 3 Ounces 200/50
Egg 1 20/5
Beef Liver 3.5 Ounces 15/4

Milk does not naturally contain vitamin D, raw or otherwise. Synthetic vitamin D is added to cow’s milk, soy milk and rice milk but there are problems with products enriched with vitamin D.

Synthetic vitamin D is only half as effective as natural and can block natural vitamin D’s effects. It can be toxic and affect calcium levels.

The precursor to vitamin D is found in both plant and animal products but animal-derived products contain the building block that we need to create calcitriol—the compound we make best use of.

Vitamin-D-fortified foods and dietary supplements mostly contain ergocalciferol (D2) rather than cholecalciferol (D3). D2 is created by irradiating yeast and other molds, D3 by irradiating animal oils and cholesterol.

D3 from animal cholesterol is closest to what sunlight produces in humans and is converted 500 times faster than D2. It’s estimated that D3 is 4 times more effective in humans than D2 and “vitamin D2 should no longer be regarded as a nutrient appropriate for supplementation or fortification of foods.”

No clinical trials have shown D2 to be effective at preventing bone fractures, for instance, while every trial of D3 does.

Some supplement manufacturers are switching over to D3 but a supplement that provides the actual food source of the vitamin, along with all of the other enzymes and compounds that naturally help us to utilize it, are more effective than the isolated vitamin alone.

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