Fat Guide
Fat-soluble vitamins: A, D, E and K
Four vitamins dissolve in fat rather than water — and that single property changes how you absorb them, how you store them, and how easy they are to overdo.
The four, and what they do
| Vitamin | Main roles | Good sources |
|---|---|---|
| A | Vision, immune function, cell growth | Liver, eggs, dairy; beta-carotene in orange and dark green vegetables |
| D | Calcium absorption, bone and muscle function | Fatty fish, fortified milk, sunlight exposure |
| E | Antioxidant protecting cell membranes | Nuts, seeds, vegetable oils |
| K | Blood clotting, bone metabolism | Leafy greens, some fermented foods |
Why "fat-soluble" actually matters
Two practical consequences follow from dissolving in fat rather than water:
- You need dietary fat to absorb them. Eating a carrot with no fat at all means absorbing much less of its beta-carotene. This is one of the concrete downsides of very low-fat diets.[1]
- Excess is stored, not excreted. Water-soluble vitamins are largely flushed out in urine when you overshoot. Fat-soluble ones accumulate in the liver and fat tissue, so high-dose supplementation — particularly vitamin A — can build to toxic levels over time.[1]
Preformed vitamin A vs. beta-carotene
These aren't interchangeable in terms of risk. Preformed vitamin A (retinol, from animal foods and supplements) can reach toxic levels. Beta-carotene from plants is converted as needed and doesn't carry the same toxicity risk.[1]
Keep reading: Vitamin D explained · Risks of very low-fat diets · Healthy high-fat foods