We’ve spent the past couple of weeks in my nutrients class learning about fat-soluble and water-soluble vitamins. It’s important to understand how these different types of vitamins work inside our bodies, so I am going to give quick overviews of each – fat today, water tomorrow.
The four fat-soluble vitamins are vitamin A, vitamin D, vitamin E and vitamin K. ADEK: pretty easy to remember.
Fat-soluble vitamins are obtained from our food. They travel through our digestive tract and then are absorbed first into the lymph, then into the blood. They require bile for absorption. Bile is produced in the liver but stored in the gallbladder, and is made up of water, cholesterol, and other bile acids and pigments (note: you NEED cholesterol to produce bile and absorb these 4 important vitamins!).
Many fat-soluble vitamins require protein carriers to help transport them once inside our blood. These vitamins are stored in our fat cells and are not readily excreted. Rather, they remain stored in our fat cells for weeks, months or even years. The positive aspect of this is that if we go through a period of poor nutrition, whether it be because we are sick or on vacation or just too busy to prepare nutritious food at home, our body can dip into the stores of vitamins A, D, E and K and use them to support our health. The downside of these vitamins being stored for longer periods of time is that it may take months or years for a deficiency to show up. If we are not obtaining enough vitamin E from our diet, or not absorbing it properly, our body will just dip into our stores and we may not know for months or years that our current diet is not supporting our health properly. Also, because fat-soluble vitamins are stored for so long, risk of toxicity can be higher.
The last thing I want to point out before giving some information on the four vitamins is this: in order to store these vitamins, we must include fat in our diets. The no-fat diet trend that has been around for a while now is (in my opinion) bad because people who eliminate fat from their diets completely will be unable to absorb and store fat-soluble vitamins, and will eventually become deficient and create a body that is out of balance. I’m not saying we should all overdose on high fat foods; however, it is okay, and even GOOD, to eat some fat with your vitamins – olive oil, butter, nuts, etc. This will help ensure you are able to fully utilize these vitamins. Don’t be afraid to make your own salad dressing with some olive oil, lemon juice, balsamic vinegar, mustard, salt and pepper. The fats are good! If you stick with the highly processed, store-bought fat free dressing, you may be denying yourself some important vitamins.
Here is a basic overview of each of the fat-soluble vitamins:
Vitamin A: Helps with vision, maintenance of the cornea, health of skin cells, bone and tooth growth, reproduction and immunity. Top food sources include calf liver, chili peppers, dandelion root, chicken liver, carrots, dried apricots, collard greens, kale, sweet potatoes, parsley, spinach, mustard greens, mangoes, cantaloupe and broccoli. Signs of a vitamin A deficiency include night blindness, dry eyes, and impaired immunity. One test my teacher told us about is the light switch test: Go into a room that is dark but not too dark, meaning you can still make out shapes, etc. Turn on the light switch and then immediately turn it back off again (so the light is only on for a flash) and notice how quickly your eyes readjust to the shapes in the dark. If they adjust quickly and easily, you have enough vitamin A in your diet. But if they take longer to adjust and you are blinded for a few seconds, you may be deficient.
Vitamin D: This is an important vitamin for bone health in that it stimulates the absorption of calcium. It also has anticancer properties. Food sources of vitamin D include fortified foods (milk, cereals, etc. – however, I recommend sticking with whole food sources), and also natural food sources such as cod liver oil, cold-water fish such as mackerel, salmon and herring, butter and egg yolks. The best source is, of course, sunshine! But remember that even an spf 2 sunblock will prevent vitamin D from being absorbed through your skin, so you must be outside with no sunblock for 15-30 minutes (depending on your skin type) before applying sunblock. Signs of vitamin D deficiency include rickets in children, and lack of bone strenth and joint pain in adults.
Vitamin E: Vitamin E is used as an antioxidant in our bodies – it stabilizes cell membranes and protects the fatty acids from lead, mercury, and other toxins such as chemicals and drugs. Food sources of vitamin E include seeds, nuts, whole grains, asparagus, avocados, berries, green leafy vegetables and tomatoes. Cooking and processing of foods greatly reduces their vitamin E content. Signs of a vitamin E deficiency include nerve damage, muscle weakness, poor coordination, involuntary movement of the eyes, and anemia.
Vitamin K: The main function of vitamin K is the synthesis of blood-clotting proteins and bone proteins. Top food sources include kale, green tea, turnip greens, spinach, broccoli, lettuce cabbage, watercress, asparagus, oats, green peas, whole wheat and green beans. Gut bacteria can also produce vitamin K, so a deficiency is rare. However, deficiency symptoms would include easy bruising, appearance of ruptured capillaries and hemorrhaging.
Tomorrow we’ll tackle the water-soluble vitamins and in the meantime, get your vitamins A, D, E and K… and don’t forget the fats!