It’s not how many vitamins you take, but how many you absorb that matters most. Some vitamins you can absorb easily because they’re water soluble or dissolve in water. These include B-vitamins and vitamin C. However, there are four vitamins that your body can’t easily take up unless you consume them with a source of fat. If you take one of these vitamins as a supplement, you might miss out on much of their benefit if you take them without food. Let’s look at the four vitamins you need fat to absorb.
Vitamin A
Vitamin A is a fat-soluble vitamin that you absorb best with a fat source. It comes in various forms called retinoids, abundant in animal-based foods, but there’s another form called carotenoids that you find in certain fruits and vegetables. An example is beta-carotene in carrots. Your body must convert beta-carotene to vitamin A, but carotenoids have benefits independent of their vitamin A activity. For example, they have antioxidant and anti-inflammatory activity. The retinoid form of vitamin A is vital for a healthy immune system, cellular health, reproduction, and for vision, especially night vision.
Since vitamin A is a fat-soluble vitamin, you need fat to absorb and get the full benefits. However, the retinoid forms of vitamin A are in foods that contain fat, particularly liver, dairy, eggs, and fish oils. So, they’re packaged in a way that helps you best absorb them. However, carotenoids are harder to absorb without eating a meal that contains fat. Foods that are high in carotenoids, like leafy greens, carrots, and squash, naturally lack fat, so they’re not prepackaged for easy absorption.
How can you make carotenoids more absorbable? When you eat a salad that contains green, leafy vegetables and other carotenoid-rich foods, add a source of fat, such as nuts or avocado, or use an olive-oil dressing.
Vitamin D
The best source of vitamin D is exposure to sunlight. Your skin converts a vitamin D precursor called dehydrocholesterol to an intermediary that your liver and kidneys convert to active vitamin D. Since many people don’t get enough sun exposure, vitamin D supplements are popular as a way to make up for the shortfall. However, you may not absorb as much of it without a source of fat.
Vitamin D absorption from supplements is a bit tricky. Studies show you’ll absorb the most by taking it with a meal that contains a low-to-moderate quantity of fat. However, too much fat can reduce the absorption of vitamin D too. The optimal amount of fat appears to be around 11 grams, as it outperformed 35 grams and 0 grams in a study.
How much does a fat-free meal reduce the absorption of vitamin D? Around 15 to 30% You’ll still absorb some but not the full amount if you don’t consume vitamin D with a fat source. Most foods don’t contain substantial quantities of vitamin D, but those that do also contain fat. These include butter from grass-fed cows, liver, egg yolks, and fatty fish. Manufacturers also fortify some products with vitamin D such as dairy milk, milk alternatives, yogurt, and breakfast cereal.
Vitamin E
Vitamin E, like vitamin A, is an antioxidant vitamin, one that fights oxidative stress and inflammation. Because of its anti-inflammatory effects, getting enough of it could lower the risk of cardiovascular disease, but vitamin E supplements may not have the same protective benefits. In fact, some research shows taking vitamin E in supplement form may be harmful.
Vitamin E comes packaged in foods that contain fat. Some of the best sources are olive oil, canola oil, almonds, meat, and dairy. So, unless you’re taking a vitamin E supplement, you’ll likely get enough fat to absorb respectable amounts of vitamin E. If you’re taking a vitamin E supplement though, take it with a meal that contains fat to enhance absorption. Check with your physician before taking vitamin E in supplement form, too.
Vitamin K
Vitamin K, a vitamin you need for blood clotting, is another fat-soluble vitamin you won’t absorb well without a source of fat. There are two main forms of vitamin K: vitamin K1 and vitamin K2. You’re probably more familiar with vitamin K1, the type in leafy greens and other green vegetables. New research suggests that vitamin K2, in grass-fed beef, natto (fermented soy product), dairy products, and eggs, may play a key role in bone and heart health. It activates an enzyme called osteocalcin that directs calcium toward bone, supporting healthy bone density, and away from the inner walls of arteries where it could contribute to cardiovascular disease.
Absorption of both forms of vitamin K is enhanced by dietary fat. Since most sources of vitamin K1 are vegetables that are low in fat or fat free, you won’t absorb as much vitamin K1 unless you add fat to your meal. For example, saute greens in olive oil. Doing this will also help you absorb more of the beta-carotene (Vitamin A precursor) from green, leafy vegetables.
If you’re taking certain types of blood thinners, your doctor may tell you to avoid eating green, leafy vegetables and other sources of vitamin K since vitamin K can interfere with the activity of blood thinners.
The Bottom Line
These are the four fat-soluble vitamins that you should take with a meal that contains fat to ensure adequate absorption. For some, like vitamin E, the food source itself contains fat while for others like vitamin K1, the source often doesn’t contain fat, so you’ll need to add some. For these vitamins, most health care providers recommend taking them with an evening meal that contains dietary fat.
References:
Examine.com. “How much fat do I need to absorb vitamin D?”
National Institutes of Health. “Vitamin A”
Clarke MW, Burnett JR, Croft KD. Vitamin E in human health and disease. Crit Rev Clin Lab Sci. 2008;45(5):417-50. doi: 10.1080/10408360802118625. PMID: 18712629.
National Institutes of Health. “Vitamin E”
Medscape Family Medicine. “Vitamin K2 Steps Into the Spotlight for Bone and Heart Health”
MedicalNewsToday.com. “Health benefits and sources of vitamin K”
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