Vitamin D

I bet you're not getting enough!

Written By Jim Stoppani, PhD

Updated December 26, 2019

Of all the vitamins, D ranks up there as my number one most critical vitamin to take.

While most of the vitamins, such as vitamin A, the B's, C, and E, are essential, vitamin D is actually a non-essential vitamin. That's because the skin produces vitamin D upon exposure to light. Sunshine triggers vitamin D production in skin by converting cholesterol into vitamin D₃.

There are actually two forms of vitamin D, vitamin D₃ (cholecalciferol) and vitamin D₂ (ergocalciferol).

The liver and kidneys are the primary sites in the body where both forms of vitamin D are converted to the active form, the steroid hormone, 1,25-dihydroxyvitamin D. Any extra D that's not needed by the body is stored in fat tissue for future use. Vitamin D₂ is found in plant sources and some supplements and can only enter the body through the diet. Vitamin D₃, which can be produced through sun exposure or from animal products, such as fatty fish, or supplementation, is the more potent form of the vitamin, as it tends to be more readily converted to the active form in the body.

In theory your body should be able to make all the vitamin D you need.

I'll repeat: in theory: But the reality is that your body does not even come close to making adequate levels of D, regardless of whether it's during sunny summer months or dark and dreary winter.

That's why it is so essential to supplement with vitamin D.

That is if you want to reap all of the benefits that D has to offer.

The most obvious role of vitamin D is in promoting bone health.

Vitamin D helps to maintain bone health by aiding calcium absorption and regulating the movement of calcium in and out of bone tissue. Without D, you would absorb less than half of the calcium you do from food and supplements.

Vitamin D also keeps your immune system up to fight off the germs like colds and flu that can beat you down and leave you missing workouts.

It's been theorized that this is one reason why the flu is so prevalent in the colder darker months of the year. With less sunshine in the winter months, most people have lower levels of vitamin D and an impaired immune system. Vitamin D is important for the immune system because it actually triggers T cells, which are the immune system's killer cells. They basically do the dirty work to "knock off" these invaders.

Vitamin D may also help to protect you from certain cancers.

One study in the American Journal of Preventive Medicine reported that women living in sunnier regions of the world had higher blood levels of vitamin D, as well as a significantly lower risk of ovarian cancer, than those in less sunny regions. Another study found that sun exposure and a diet rich in vitamin D lowered the risk of breast cancer. And sunshine exposure has also been correlated with lower risk of colon cancer.

Vitamin D also has benefits all around for the brain.

Low levels of vitamin D are associated with psychiatric and neurological disorders, as well as a bigger cognitive decline with aging. One study from Washington University School of Medicine (St. Louis) reported that vitamin D deficiency was associated with depression and diminishing cognitive performance. In fact, Georgia State researchers reported that individuals with vitamin D deficiency have an 85% greater risk of developing depression.

In addition to the many health benefits covered above, vitamin D has several physique and performance benefits as well. Considering that Vitamin D actually gets converted in the body to a steroid hormone, it makes sense that it would have effects on muscle fibers.

Vitamin D can help to increase muscle strength and muscle size.

The active form of Vitamin D binds to specific receptors found on muscle cell membranes and in muscle cell nuclei. When it binds to these receptors it enhances muscle contraction and protein synthesis, which is the build up of muscle protein. Research shows that certain types of these receptors may be responsible for greater muscle size and strength. Although you can't alter the type of Vitamin D receptors you have in your muscles, making sure you have adequate Vitamin D levels in your body can help ensure your muscle vitamin D receptors are activated for optimal muscle function, strength and muscle growth.

Vitamin D can help to reduce body fat.

One study reported that college females at the University of Southern California with lower blood levels of vitamin D had significantly higher levels of fat in their muscles than those with high blood levels of vitamin D. You can store body fat under the skin, as well as in your muscles. Having fattier muscles not only means that you have more body fat, but it can also result in weaker muscles with less endurance. The higher fat content of the muscle impairs mitochondrial function, so the muscles produce less energy and can lead to reduced insulin sensitivity. Although they're not sure precisely how vitamin D prevents fat accumulation in muscle, it is well known that vitamin D and calcium work together to encourage fat loss. One recent study published in the journal Clinical Nutrition reported that when men and women consumed a breakfast containing over 500 mg of calcium and about 350 IU of vitamin D, they burned up more calories and fat, and ate 320 calories less throughout the day as compared to when they started the day with a breakfast containing about half as much calcium and D.

Vitamin D is critical for maintaining high testosterone levels.

Since vitamin D is produced in the body from cholesterol, as is testosterone, it makes sense that higher vitamin D levels can encourage higher testosterone levels in men. In fact, Austrian scientists from the Medical University of Graz reported that men with higher blood levels of vitamin D had significantly higher levels of testosterone and lower levels of sex-hormone binding globulin (SHBG) than those with low levels of vitamin D in their blood. Having lower SHBG means that more of that testosterone produced is free to get in the muscles and increase muscle growth. But that doesn't mean that vitamin D necessarily raises testosterone levels. That's why this group of researchers did a follow up study on men to see if vitamin D supplementation actually could raise testosterone levels. And would't you know it, it did! The Austrian researchers reported in a recent issue of Hormone and Metabolic Research that the men receiving just over 3300 IU per day of vitamin D for one year had a 25% increase in testosterone levels while those getting a placebo had no such rise.

That's right, supplementing with a high dose of vitamin D raised testosterone levels by 25%!

Jim's Vitamin D Dosing Recommendations:

To take advantage of all that vitamin D has to offer, such as increased bone health, better immune function, enhanced mood and brain function, higher testosterone levels, increased muscle size and strength, and less body fat, I recommend that go with 2000-6000 IU per day taken with meals. Your best bet is to take it with calcium. Since you can only absorb about 500-600 mg of calcium at a time, I suggest you take vitamin D and calcium two to three times per day. For example, take 1000-2000 IU of vitamin D and 500-600 mg of calcium with breakfast, lunch and dinner. That will nab you a total of 3000-6000 IU of D and 1500-1800 mg of calcium. By the way, high doses of calcium have been found to also raise testosterone levels in men. So guys, be sure to take it!

Regardless of what brand of vitamin D you use, be sure that you supplement with D3. One study from Creighton University reported that D3 supplements were about 90% more potent at raising levels of 25-hydroxyvitamin D, the storage form of vitamin D in the body, than vitamin D2. It also increased stored levels of the vitamin three times more than D2 did.

One note for those taking medication:

If you take any medications regularly, you may want to notify your doctor that you are taking high doses of vitamin D. Vitamin has been found to activate a gene for a liver enzyme known as CYP3A4 that metabolizes about half the drugs routinely prescribed. Don't worry, there's no danger in taking vitamin D with medications. The only problem is that with higher levels of the liver enzyme, your body will break down some medications more quickly, meaning that you may have to take a higher dose. Of course, the sad news is that your doctor will likely have no idea about this. Hopefully, if you do have to take medication, your doctor is the type who keeps up with research.

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