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Editor’s Note: This post was updated on November 10, 2018for accuracy and comprehensiveness. It was originally published on August 9, 2017.

Does your daily vitamin routine work? There are conflicting reports.

Some experts tout the benefits of daily vitamins while others consider supplements to be a waste of money and believe these nutrients should come from your diet and regular sun exposure.

Vitamin D deficiency receives a lot of attention because of claims it can prevent a wide range of deadly diseases like cancer, diabetes, and heart disease.

Media coverage of “the need to get enough vitamin D” is so widespread that a 2014 study in the British Medical Journal thought it noteworthy to examine what was being reported. Many news articles framed vitamin D deficiency as a cause of widespread concern and claimed “‘it is impossible to get vitamin D from natural sources’” from just sunlight exposure and diet alone. News sources also made sweeping recommendations–over half the articles asserted that “‘daily supplementation may be necessary for good health.’”

Reported health benefits include:

This attention-grabbing headline is too broad to apply to everyone (more research is needed linking blood pressure) but there’s clear evidence of health benefits for older adults.

In this article, we’ll break down the science behind vitamin D supplementation, identify who may benefit, and how supplements can support healthy aging: muscle growth, fall prevention, and blood sugar regulation.

What Exactly Is Vitamin D?

Vitamin D is a fat soluble nutrient that can be acquired in several ways and supports normal physiologic functions including absorption of minerals such as calcium and zinc. Nature provides this nutrient in two ways: consuming food or supplements and sun exposure

With the exception of fatty fish, most foods in a regular diet provide a relatively small amount. Examples of natural food sources include:

  • Salmon
  • Swordfish
  • Egg yolk
  • Fortified foods, including some milk, orange juices, and yogurts

When your skin absorbs sunlight, your body naturally produces vitamin D through a series of chemical reactions. Be aware that the time of day, cloud cover, sunscreen, and skin melanin content can all affect production, so it’s not always a reliable source.

Aside from nature and food sources, the third common source is manufactured dietary supplements. How much vitamin D you get from a supplement is measured using International Units (IU). However, dietary supplements are not regulated by the Food and Drug Administration, so when buying any supplements, look for brands that have been certified by an independent company to ensure they contain the listed amount of nutrients.

The vitamin usually comes in two main forms: vitamin D2, and vitamin D3. Vitamin D2 is commonly found in fortified foods while Vitamin D3 can be found from animal food sources and sun exposure. Without getting into the chemistry of these two forms, it’s important to know that vitamin D2 may have lower potency. So if you are choosing to supplement, you may want to stick with vitamin D3.

After Vitamin D enters your body, it goes through your liver and kidney and gets converted into its active form,  known as a prohormone, which is is then circulated in your blood. Prohormone is essential to normal physiological function and supports the skeletal muscle system.

Building Muscle – The Vitamin D Approach

Vitamin D has long been known to play an important role in bone health, but more recently it has been reported to influence muscle quality. This could have important implications for adults as they age.

Skeletal Muscle Mass tends to decrease as we age, primarily as a result of decreasing activity. Muscle loss diminishes functional performance on tasks requiring strength and coordination. When this loss of muscle mass becomes significant enough, it becomes a condition known as sarcopenia which can impact your ability to live independently.  But there is hope. Treatments which include proper nutrition, exercise, and yes, vitamin D supplementation was found to not only slow down muscle loss but help regain muscle mass and strength.

But what reports that older adults that skeletal muscle receptors for vitamin D decrease with age. How can older adults take advantage of supplementation if their muscles have fewer receptors?

There is strong evidence that Vitamin D supplementation may still be effective, especially in older adults whose blood levels are moderately low.

One study found that supplementing with 4,000 IU per day increased muscle fiber size after just 4 months, even without weight training. Not only that, but the most substantial gains were made in type II muscle fibers. These are the fibers responsible for short bursts of movement like getting up out of a chair or lifting something overhead.

Another study found that taking 1000 IU of vitamin D daily resulted in a whopping 25% increase in leg strength along with an increased concentration of the nutrient in the blood. This kind of improvement could be important for helping older adults maintain independence as they age.

But don’t neglect the importance of resistance training to support healthy aging. A daily dose of vitamin D can support muscle repair and recovery from exercise, and result in quicker adaptation and even better chance to gain muscle mass.

Can Vitamin D Keep You on Your Feet?

Falls are the number-one cause of fatal and nonfatal injury among older adults, and low vitamin D levels may be partly to blame.

Although it may not directly linked, there is strong correlation that vitamin D deficiency may increase fall risk in older adults.

The connection likely has to do with the effects on muscle strength and function. A trial involving nearly 250 older adults found that a daily vitamin D (plus calcium) supplementation improved quadriceps strength, postural control, and daily functions, like standing up and walking, after one year.

Most impressively, falls decreased by over 25% after 12 months compared with patients who only received calcium, and by almost 40% after 20 months. Not only did the supplements help these people counter the effects of aging and inactivity on their muscle, but it was important in the prevention of a potentially disastrous fall that could result in injury.

The benefit of supplementing may be especially noticeable in people who have a history of falls. One study showed that recurrent falls were significantly lower in people taking a supplement with vitamin D and calcium, compared with calcium alone. Improvements in muscle strength and function seem to be especially important for this group, since improving vitamin D status resulted in an increase in strength and functional performance and a decrease in fall risk.

But does all this mean older adults can just rely on vitamin D to reduce their fall risk and forget about regular strength training sessions?

Absolutely not.

It is probably best to think of getting enough vitamin D as an extra step you can take to supplement your exercise and strength training routine that will keep you upright and your muscles healthy.

Keeping Your Blood Sugar in Check

With the tremendous benefits that Vitamin D has on your muscle health, it’s no surprise that researchers have a link connecting muscle mass, vitamin D status, and blood sugar. Insulin, the hormone that allows blood sugar into your muscles, tends to be better in people with greater muscle mass. People with blood vitamin D levels over 26 ng/dL had a significantly lower risk of hyperglycemia than those below recommended levels.

That association does not necessarily mean this is the only thing you need to do to keep your blood sugar low. But research shows a daily vitamin D supplements in combination with calcium slowed the long-term rise in blood sugar in people with prediabetes.

Although adequate vitamin D levels may prevent the progression of hyperglycemia, the jury is still out on the effectiveness of supplementation for people with diabetes. It could be worthwhile to monitor blood for vitamin D levels and look out for any deficiency. Research indicates that supplementation is beneficial in people who are classified as having deficiency, although not for people who have an insufficiency or normal levels.

So, How Much Do I Need?

National guidelines say adults should target a dietary intake of 600 – 800 IU per day. For most healthy adults, sunlight and nutrient-rich diet may just be enough to maintain blood levels at an adequate level. Remember that vitamin D occurs naturally in foods that provide a range of other nutrients, so supplements are never a substitute for a healthy and diverse diet. But due to the risk of skin cancer from sunlight exposure, it is probably safer to obtain your vitamin D from dietary sources. Many of the studies that show a benefit from supplementation in aging populations deliver around 800 IU per day, but the dosages vary widely.


When considering a vitamin D supplementation, remember that the media attention is probably blown out of proportion. If your diet contains foods rich in vitamin D like salmon and fortified cereals and you receive daily sun exposure, you probably won’t receive any noticeable benefits from supplements.

But if you are concerned about vitamin D deficiency as you age, keep in mind that maintaining adequate levels is important in the prevention of:

  • Muscle mass and strength loss
  • Elderly Falling
  • The progression of hyperglycemia

While supplements can be beneficial for older adults, it can also benefit pregnant women and people trying to lose weight. Since various groups of people may need vitamin D supplements in an addition to daily sunlight exposure and diet, regularly monitoring levels (as well as other nutrients) and your body composition is always important to prevent the development of diseases and support a healthy lifestyle.


Max Gaitán, MEd is an exercise physiologist and a USA Triathlon Certified Coach. When he’s not coaching, studying, or writing, Max spends most of his time outdoors training for triathlons.

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