Vitamin D is fat-soluble, so it absorbs better when fat is present. Some supplements build that in with a carrier oil. Many do not: dry tablets, powders, and most gummies contain little or no fat, which leaves absorption depending on whatever you happen to eat alongside them. Where a carrier oil is used, which oil it is tends to be decided on cost rather than on anything to do with you.
The short version:
- Vitamin D absorbs better with fat present.
- Some formats build fat in. Dry tablets, powders, and most gummies do not.
- Most products use whichever oil is cheapest at scale.
- Gummies solve the taste problem by adding sugar and other ingredients.
- The carrier position is a good test of how a brand thinks about formulation.
WHY THERE'S OIL IN THERE AT ALL
Vitamin D is fat-soluble. It does not dissolve in water and it needs fat present to cross from your gut into your bloodstream. Research has found that peak vitamin D3 absorption was significantly higher when taken with a fat-containing meal than with a fat-free one.
Which gives supplement makers a decision to make. Either build fat into the product, or leave it to chance and hope the customer takes it with the right meal. Softgels and liquid drops build it in. Dry tablets and most gummies do not.
The carrier is not packaging. It is part of how the vitamin gets into you.
WHAT ENDS UP IN THE CARRIER POSITION
Once a manufacturer decides they need an oil, the question becomes which one. And the honest answer, in most cases, is whichever is cheapest at industrial scale.
That is not a scandal, it is just economics. But it is worth understanding what you are actually choosing between:
| Format | Typical carrier | What else is usually in there |
|---|---|---|
| Softgel | Whichever oil is cheapest at volume | Gelatin or glycerin shell, sometimes colorings |
| Dry tablet | None | Binders, flow agents, coatings |
| Gummy | Little to none | Sugar or sweeteners, gelatin or pectin, flavorings, colorings |
| Liquid drops | An oil, quality varies widely | Depends entirely on the brand |
The gummy case is the clearest illustration. To make a fat-soluble vitamin taste like candy, you have to add the things that make candy. That is a real trade-off, and it is rarely presented as one.
THE THING A LABEL ACTUALLY TELLS YOU
Read the full ingredient list, not the front of the bottle. Three questions:
- How many ingredients are there? A short list is a design decision. A long one usually means the formulation is solving problems other than absorption, like taste, shelf life, or appearance.
- Is the carrier named specifically? "Vegetable oil" is not a specific answer. A brand that has thought carefully about the carrier will tell you exactly what it is.
- What is there for your benefit versus the manufacturer's? A carrier oil aids absorption. Colorings and sweeteners aid sales.
The reason this matters beyond the oil itself: what a brand puts in the carrier position is a reasonable proxy for how it makes every other decision. If the cheapest option won there, it probably won elsewhere.
WHAT D3X USES, AND WHY
Three ingredients. Vitamin D3, vitamin K2 as MK-7, and organic olive oil.
Olive oil is not the cheapest option available. It was chosen because it is a fat, which is what the vitamin needs, and because we would rather name a specific, recognizable ingredient than a generic category. There is no sweetener, no coloring, no flavoring, and no filler, because in a liquid dropper format none of those are necessary.
The bottle is glass rather than plastic. The full ingredient list fits in one line.
That is the whole formulation argument: not that other things are dangerous, but that a fat-soluble vitamin needs a fat, and everything past three ingredients is solving a problem we chose not to create.
See the product, or read the related pieces on why vitamin D needs fat to be absorbed and liquid versus capsule.
Sources
Dawson-Hughes B, et al. "Dietary Fat Increases Vitamin D-3 Absorption." Journal of the Academy of Nutrition and Dietetics, 2015.
National Institutes of Health, Office of Dietary Supplements. "Vitamin D: Fact Sheet for Health Professionals."
About D3X. D3X makes one thing: a liquid vitamin D3 + K2 (2,000 IU D3 / 100 mcg K2 as MK-7) in an organic olive oil base, in a glass bottle, third-party tested and made in the USA. Learn more.
*These statements have not been evaluated by Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Frequently Asked
Why is there oil in vitamin D supplements?
Vitamin D is fat-soluble, so it absorbs better when fat is present. Research has found peak vitamin D3 absorption is significantly higher when taken with a fat-containing meal than a fat-free one. Some supplements build fat in with a carrier oil; dry tablets, powders, and most gummies do not.
What carrier oil is best for vitamin D?
What matters most is that a fat is present at all, since that is what absorption requires. Beyond that, the useful test is whether a brand names its carrier specifically rather than listing a generic category like vegetable oil.
Do vitamin D gummies have fillers?
Gummies typically contain sugar or sweeteners, gelatin or pectin, flavorings, and colorings, because those are what make a supplement taste like candy. They also generally contain little fat, which is what a fat-soluble vitamin needs.
How many ingredients should a vitamin D supplement have?
There is no rule, but a short list is a useful signal. A longer list usually means the formulation is also solving for taste, shelf life, or appearance rather than only for absorption.
What is in D3X?
Three ingredients: vitamin D3, vitamin K2 as MK-7, and organic olive oil. No sweeteners, colorings, flavorings, or fillers, in a glass bottle.
