Many people are not aware that there are two types of vitamins, at least in regards to absorption.
The first group is water-soluble vitamins. They’re called “water-soluble” because they only require water to be absorbed and transported. Since our body has plenty of water, absorption isn’t usually a problem. The group of water-soluble vitamins includes all the B vitamins (B1/thiamin, B2/riboflavin, B3/niacin, B6, folate, B12), vitamin C, and several more. They’re essential, but that’s not what this post is about.
The second group of vitamins is said to be “fat-soluble”. As you may have guessed, they require more than water to be absorbed – they require fat. Fat molecules act as helpers for these vitamins to be absorbed in the intestines. Here’s a quick summary of the fat-soluble vitamins:
Functions: Promotes vision and also has roles in reproduction and growth.
Sources: Deep orange (like carrots and sweet potatoes) and dark green (like broccoli and spinach) vegetables are great sources. Beef liver and egg yolks are especially high in vitamin A and contain fat to enhance absorption.
Functions: Bone growth is the primary function, but some research indicates vitamin D is important in immunity, brain health, and possibly even fighting tumor development.
Sources: Our body can create its own vitamin D with moderate exposure to sunlight; luckily, you don’t need to eat fat to absorb this form of vitamin D. Dietary sources include fortified dairy products, egg yolks, liver, and fatty fish such as salmon and sardines.
Functions: It’s an important antioxidant, helping to prevent chronic diseases and inflammation.
Sources: Vegetable oils, leafy greens, whole grains, nuts, seeds, liver, and egg yolks.
Functions: Facilitates blood clotting and assists with building bones.
Sources: Your body can actually obtain vitamin K from bacteria in your intestines! Food sources include leafy greens, Brussels sprouts, and liver.
Another difference between fat-soluble and water-soluble vitamins is how they’re stored. Fat-soluble vitamins can be stored for relatively long periods of time in the liver and adipose tissue (body fat), while water-soluble vitamins are easily excreted via urine. This means that water-soluble vitamins need to be consumed more consistently, while a single, large intake of a fat-soluble vitamin can last someone for days, weeks, or even months. It also means, however, that fat-soluble vitamins can reach toxic levels much more easily than water-soluble vitamins.
What’s the takeaway? Your body needs fat for a variety of reasons, but absorbing and transporting these essential vitamins is a major one. Eating a meal of plain vegetables is unlikely to lead to your body obtaining these vitamins, so including fat as a boost for absorption is beneficial. Keep in mind the fat source doesn’t need to be directly on the vegetables, it just needs to reach your stomach around the same time.
With recommendations for vitamin D supplementation continuing to increase, it’s also important to note that these supplements should be taken with a meal or snack – otherwise you risk missing out on the benefits this nutrient provides.