Vitamin D

Vitamin D3 vs. Vitamin D2

Vitamin D2 and vitamin D3 are chemically similar and are both well-absorbed in the gut. Where they differ significantly is in their sources:

• Vitamin D2 is naturally found in mushrooms, including shiitake, Portobello, and crimini mushrooms. The vitamin D content increases when these mushrooms are exposed to UV radiation.1
• Vitamin D3 is naturally found in animals and animal-derived products like milk. It is also directly synthesized in the skin when it is exposed to ultraviolet B (UVB) radiation.6

  MedlinePlus. Cholecalciferol (vitamin D3).

Aside from the fact that vitamin D3 is likely easier to consume in your day-to-day diet, unless you are a vegetarian or vegan, vitamin D3 has proven superior to vitamin D2 in two other important ways:

• Vitamin D3 has better bioavailability, meaning more of the vitamin enters the bloodstream and can be used by the body
• Vitamin D3 has a better half-life, meaning it stays in circulation for longer

On the downside, vitamin D3 in supplements has historically been synthesized using lanolin derived from sheep’s wool. This makes it unsuitable for those who choose to avoid animal-based products.

With that said, some manufacturers have been able to synthesize vitamin D3 from algae and lichen.

Vitamin D3 For Those Without Deficiency

Beyond its use in treating vitamin D deficiency, vitamin D3 may offer health benefits to certain people without such deficiency—in particular, those with high blood pressure or osteoporosis.

Hypertension

Hypertension, more commonly known as high blood pressure, is cardiovascular disease commonly seen in people with vitamin D deficiency.

Recent studies suggest that vitamin D3 may help lower blood pressure in people with hypertension and vitamin D deficiency as well as certain groups of people with hypertension only.

According to a 2019 review of studies in the journal Medicine involving 1,687 people, vitamin D3 was able to significantly reduce systolic (“top number”) blood pressure in people over the age of 50 and those with obesity.7

This is important because isolated systolic hypertension can increase the risk of stroke, heart disease, and chronic kidney disease over time.

Osteoporosis

Osteoporosis is a frequent consequence of long-term vitamin D deficiency, so common wisdom would suggest that vitamin D supplements may help prevent or slow the progression of this common, aging-related bone disease. There is some evidence to support this claim.

A 2013 study from the University of Western Australia found that the use of vitamin D3 in nursing home residents aged 70 and over significantly reduced the incidence of hip fractures. In addition, low-dose vitamin D3 (400 IU) also increased bone mass density in the femoral (thigh) bone.8

Sources of Vitamin D3

Whether you are nutritionally deficient or simply want to meet your recommended daily allowance (RDA) of vitamin D, you can obtain ample supplies of vitamin D3 from animal-based foods, dietary supplements, and sun exposure.

Dietary Sources

Food should always be the first source of vitamin D. Here are some of the best dietary sources of vitamin D3 to bolster your intake:

Some manufacturers of fruit juices, dairy products, margarine, and plant-based milk add vitamin D3 to boost their product’s nutritional value, as well.

Supplements

As convenient as they are, supplements should never be your primary source of vitamin D (or any nutrient, for that matter). They are really only intended for when you are not getting enough from your diet.

Vitamin D3 is readily available in supplement form and sold as capsules, softgels, gummies, and liquid drops. Most are formulated in doses higher than you need per day—between 2,000 and 10,000 IUs—but this is not a concern as only a portion will be absorbed. The rest will be passed in urine.

Talk to your healthcare provider about the best dose for you based on your age and medical history.

Sun Exposure

Vitamin D3 is unique in that (unlike vitamin D2) you can get it from the sun.

When exposed to UVB light, an organic compound in the skin called 7-dehydrocholesterol will activate and start churning out vitamin D3. The rate of production can vary by your age and skin tone, with older people and those with darker skin getting the least benefit.

Sunscreen can also decrease production by blocking both UV rays.

Getting a little sunlight every day can help you maintain your vitamin D levels, but it’s not the safest or most reliable way to get it given the risk of skin cancer.

Possible Risks

Vitamin D3 is generally regarded as safe, but it can on rare occasions cause toxic effects if you take too much. This is referred to as hypervitaminosis D.10

With vitamin D toxicity, the balance of minerals like calcium and potassium is upset. This can lead to a condition known as hypercalcemia, in which too much calcium builds up in the body. This can lead to symptoms like:10

• Stomach upset
• Nausea
• Vomiting
• Constipation
• Bone pain
• Muscle weakness
• An increased risk of bone fractures

Vitamin D toxicity was common in the 1940s when daily doses of 200,000 to 300,000 IUs per day were commonly recommended to treat chronic illnesses like tuberculosis and rheumatoid arthritis.10

Today, vitamin D toxicity is considered a rare occurrence.

Recent studies have shown that vitamin D3 doses of 20,000 IUs per day are tolerable in adults with no signs of toxicity.10

Summary

Vitamin D helps you absorb calcium and phosphate from food. It is important for bone and muscle strength and immune function, and it may have other benefits such as helping prevent inflammatory disease.

There are two types; vitamin D3 is more efficient in terms of how it can be used in the body than vitamin D2. You can get vitamin D from food or supplements, and your body can make D3 when exposed to sunshine.