What Is Vitamin D3? A Plain-Language Ingredient Guide

The short answer: a vitamin with a long chemical name

Vitamin D3 is one form of vitamin D, a nutrient that belongs to the group of oil-soluble vitamins. Its chemical name is cholecalciferol, which is the word you will often find in brackets on a Supplement Facts panel. If you have ever wondered why a label says Vitamin D3 (as cholecalciferol), the answer is simple: the first part is the common name, and the second part tells you exactly which compound the manufacturer used.

Vitamin D is a little unusual in the vitamin world. Most vitamins are things we only obtain from what we eat or drink. Vitamin D, by contrast, is a compound that animals and people can also form naturally when sunlight reaches the body, which is why it is sometimes called the sunshine vitamin. That nickname is a handy way to remember it, though it does not tell you anything about how the vitamin is made into a capsule ingredient.

In this guide we stay with the basics: what vitamin D3 is, which foods carry it, how the different forms are named, and how it appears on a label such as the one on a bottle of LungFresh. It is an explainer, nothing more.

D2 and D3: two members of the same family

Vitamin D is really a family name. The two forms you are most likely to meet on shelves are vitamin D2 and vitamin D3. They are close cousins with slightly different chemical structures and different origins.

Vitamin D2 is known as ergocalciferol. It originates from plant and fungal sources, for example mushrooms that have been exposed to ultraviolet light. Vitamin D3, or cholecalciferol, is the form associated with animals, and it is also the form made when sunlight reaches the body of people and other animals.

Because the two names look alike, labels can be confusing at first glance. A quick way to keep them straight is to remember that the number in the name matches the second half of the chemical name: D2 goes with ergocalciferol, D3 goes with cholecalciferol.

• Vitamin D2: ergocalciferol, usually from fungal or plant sources
• Vitamin D3: cholecalciferol, the animal-associated form and the one named on the LungFresh label
• Both belong to the same vitamin D family and both are listed under the heading Vitamin D on a Supplement Facts panel

Where vitamin D3 occurs in food

Natural food sources of vitamin D3 are fewer than for many other vitamins, which is one reason people pay attention to it on labels. The foods usually named are oily fish such as salmon, sardines, herring and mackerel. Egg yolks and some organ meats contain smaller amounts. Cod liver oil, a traditional kitchen-cupboard product in many countries, is another widely known source.

Many everyday products are also fortified, meaning vitamin D has been added during manufacturing. Depending on the country, this can include milk, plant-based milk alternatives, breakfast cereals and some spreads. Reading the ingredient list or the nutrition panel will show whether a particular product has had vitamin D added.

If you follow a plant-based way of eating, you may have noticed that traditional food sources of D3 are mostly animal-derived. Some supplements therefore use a form of D3 obtained from lichen, a type of organism that is not an animal. Where a product is suitable for vegetarians, the label or the brand description generally says so, so it is worth checking the packaging for that detail.

How vitamin D3 appears on a label

On a Supplement Facts panel, vitamin D usually appears as one of the first lines in the vitamin section. You may notice it written in several ways, such as Vitamin D3, Vitamin D3 (cholecalciferol) or Vitamin D (as cholecalciferol). All of these refer to the same thing.

The amount may be shown in micrograms, abbreviated mcg, or in International Units, abbreviated IU. Labels in the United States have been moving toward micrograms, but you may still find both on the same panel. As a conversion fact, one microgram of vitamin D equals 40 IU. The panel also usually shows a percent Daily Value next to the amount, which is a standard reference figure and not a promise about anything.

LungFresh lists Vitamin D3 (cholecalciferol) among its named ingredients, alongside Vitamin E, Selenium and a botanical blend. The exact amounts are printed in the Supplement Facts panel on the bottle, so that is the place to look rather than any web page or blog post, including this one.

Why it appears in capsule formulas

Vitamin D3 is a very common ingredient in daily supplements, partly because it is well known and easy to recognize on a label. Brands often pair it with other named nutrients so that one capsule routine covers several line items on the panel.

In the case of LungFresh, the brand describes the product as a daily dietary supplement in capsule form. The suggested use is two capsules a day with a glass of water, about six to eight ounces, or as the label directs. A bottle holds 60 capsules, which makes a 30-day supply at that pattern.

Because vitamin D is oil-soluble, some people like to pair a capsule routine with a regular meal. That is simply a matter of personal habit and convenience, and the bottle label remains the guide to how to take the product.

Reading and comparing labels with ease

When you compare supplements, a few small checks make vitamin D entries easier to understand. First, look for the form: D3 or D2. Second, check the unit: mcg or IU. Third, look at the serving size at the top of the panel, because amounts are always listed per serving, not per capsule unless the serving is one capsule.

With LungFresh, the serving is two capsules, so the figures on the panel refer to that pair together. A bottle of 60 capsules gives 30 servings.

It also helps to ask a few practical questions of any product: is the form named, is the unit stated, and are the other ingredients listed in a way you can follow? A label that answers those questions makes shopping calmer and quicker.

• Find the form: D2 or D3
• Check the unit: mcg or IU
• Check the serving size before comparing amounts
• Look at the other ingredients and the suggested use line