Did You Know Just That Many Cancers Are Linked To A Vitamin Deficiency?

Fat-Soluble Vitamins and Cancer

By Maureen, M.S., and Daniella Chace, M.S.
WebMD Medical Reference from "What to Eat if You Have Cancer"

Fat-soluble vitamins are intimately related to lipids. They need fat to be absorbed, and when cancer treatment interferes with fat absorption, a deficiency of these vitamins may occur. This chapter explains how the fat-soluble vitamins protect healthy tissues while enhancing the strength of the immune army.

There are four families of fat-soluble vitamins: vitamin A, vitamin D, vitamin E, and vitamin K. These vitamins need to be dissolved in fat before they can be absorbed in the intestine. Low-fat and low-calorie diets, whether by chance or by purpose, risk not providing enough of these vitamins.

Dietary fats and the fat-soluble vitamins are absorbed into the lymph vessels, bypassing the portal blood system that takes water-soluble nutrients to the liver. After a long climb up to your shoulder, they are dumped into the left subclavian artery.

Vitamins A and D can be toxic in large amounts when taken over a long period. They are stored in fatty tissues and the liver, and they can accumulate over time. Unlike vitamin C and the B complex, the fat-soluble vitamins are very stable. They are better able to stand up to the heat of cooking and processing.

Vitamin A, Retinol, Retinal, Retinoic Acid, Retinyl Esters

The vitamin A or retinoid family contains several forms, natural and synthetic, that have vitamin A activity. In addition, a number of vegetable foods contain compounds that the body can convert into vitamin A, such as the alpha, beta, and gamma carotenes. Absorption of retenol requires bile, pancreatic enzymes, and antioxidants. In the form of retinoic acid, it is absorbed directly. A six-month supply of vitamin A is stored in the liver as retinyl esters.

Vitamin A can be toxic in dosages over 15,000 RE, but much of this toxicity can be prevented by also taking vitamin E. Vitamin E and vitamin A work together.

Vitamin A can promote differentiation in epithelial cells and regression of premalignant lesions. It inhibits the development of cancerous tumors. A lack of vitamin A will decrease antibody formation, while vitamin A supplementation increases cytotoxic action of T cells, NK cells, and macrophages.

Fat-Soluble Vitamins and Cancer

Vitamin D, Cholecalciferol (D3), Ergosterol (D2), Calcitriol

The vitamin D family has two possible sources: preformed from the diet and synthesized by the skin. Vitamin D is called the sunshine vitamin, because the large amounts of the precursor 7-dehydrocholesterol in the skin, when exposed to the ultraviolet light from the sun, are converted into cholecalciferol (vitamin D3). It is estimated that up to 80 percent of the body's needs for vitamin D can be obtained this way. How much is produced depends on how much melanin pigment is in the skin (melanin competes with the precursor for the light), how much skin is exposed, and how much sun reaches the skin. This means that dark-skinned people who live in cold climates (reducing skin area open to sun) and any people who live in low-sun areas (Seattle or England, for example) probably cannot rely on manufacturing enough of their own vitamin D. The elderly are also at risk, since they often cannot get out and do not eat fortified foods.

Vitamin D is a hormone that regulates mineral balance. It stimulates intestinal absorption of calcium and phosphorus, works with the parathyroid hormone to mobilize calcium from bone, and stimulates the reabsorption of calcium from the kidneys. It also plays a role in cellular differentiation and development.

Sources of vitamin D include sunshine, fortified cows' milk and soymilk, deep-sea fish and fish oils, and egosterol in plants.

Vitamin E, Tocopherol, Tocotrienol

The vitamin E family is a group of eight closely related fat-soluble compounds made up of four tocopherols (alpha, beta, delta, gamma) and four tocotrienols. Vitamin E is stored in all areas of the body in fatty deposits, the liver, and the muscle. Eating a lot of linoleic acid and polyunsaturated fatty acids decreases the amount of vitamin E absorbed by reducing the micelle formation which is necessary for absorption. Vitamin E is an antioxidant. It works in partnership with vitamin C, protecting the lipids in the cell as vitamin C protects the watery contents. It protects vitamins A, C, and the carotenes from oxidation.

Vitamin E may protect healthy cells from some of the toxicity of radiation therapy and decrease the toxicity of certain chemotherapy drugs. It also appears to stimulate the immune system and protect the lipids in the cell membrane from damage.

Sources of vitamin E include wheat germ oil, germ of cereals, egg yolk, and nuts.


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