Difference between fat-soluble and water-soluble vitamins - and why it matters

If you promised that 2026 was the year you’d get a handle on your health, then you may have already stocked your supplement cupboard to the brim.

But did you know that there are two types of vitamins: water-soluble and fat-soluble vitamins? And the ones you’re choosing to swallow may be doing more harm than good?

Here’s everything you need to know about the essential nutrients, including why taking a ‘food-first approach’ to your dietmay be a safer bet.

What are water-soluble vitamins?

Vitamins such as C and B-complex (thiamine, biotin, folate, among others) are classed as water-soluble vitamins, essentially meaning they dissolve in water.

Unlike fat-soluble vitamins, they can be destroyed by heat or when exposed to the air. Moreover, they can be lost in water, which is why you should use other cooking methods than boiling when preparing vegetables.

It's worth knowing the risks that your vitamins pose (Getty Stock Image)

It’s important to note that water-soluble vitamins aren’t stored in the body and must be consumed each day, as per CSU Extension.

If your body doesn’t need the entire dose, then it will be processed by the kidneys and disposed of via urine.

Good sources include, but are not limited to:

• vitamin C: citrus fruits, broccoli, peppers
• vitamin B-complex: meat, eggs, legumes, and milk

What are fat-soluble vitamins?

Fat-soluble vitamins are only absorbed with the help of fats in the diet. They are stored in the body's fatty tissue and in the liver for long-term use, as per the National Cancer Institute.

Vitamins A, D and E fall into the fat-soluble vitamin category. They are essential for your body to function properly and are used to support the immune system, as per Dr Qianzhi Jiang, a pediatric and family dietitian.

If a doctor diagnoses you with a deficiency, then you have to be extra careful. This is because your body doesn’t get rid of fat-soluble vitamins right away, meaning ‘levels can remain high for weeks to months, even if intake stops’, dietitian and founder of Prime Women Nutrition, Jiliana Vocca, told Prevention.

Fat-soluble vitamins can stay in the body for a prolonged period of time, warned an expert (Getty Stock Image)

“Supplementing with fat-soluble vitamins is appropriate when a diagnosed deficiency exists, or with certain medical conditions, such as celiac disease, cystic fibrosis, or pancreatitis,” added Vocca.

Vocca advises anyone who wants to up their fat-soluble vitamin intake take a food-first approach.

“Nutrients from whole foods are generally safer and more effective,” she explained.

She also explained that it’s possible for vitamin K to interfere with medications, such as blood thinners, so it’s worth checking with your health provider before you begin taking supplements.

Good sources include, but are not limited to:

• vitamin A: dairy, eggs, oily fish, sweet potatoes, and kale
• vitamin D: red meat, breakfast cereals, milk, and fat spreads
• vitamin E: plant-based oils, nuts and seeds, and spinach

Vitamin toxicity

Fat-soluble vitamins have a higher potential for toxicity than do water-soluble vitamins, according to experts at Medscape.

Too much of a good thing can cause symptoms such as severe nausea, kidney damage, joint pain, and in serious cases even death.

Vocca told the outlet that toxicity is most likely to happen when consuming vitamins A and E. This is because the pair ‘share an absorption and transport pathway’.

“Large amounts of one can shift the body’s demand for the other,” she added.

Too much vitamin A can lead to dry skin, hair loss, fatigue, loss of appetite, nausea, and vomiting.