Topic of Current Interest
Colorectal cancer and Supplements
(Previous topics are available in the Archives)
Colorectal cancer is the second leading cause of cancer death in the United States. Polyps, which look like little round bumps and sometimes increase into large growths, are the building blocks of cancer. Several factors may influence the development of polyps. Obesity, cigarette smoking and red meat are linked with colon and rectal cancer. Other dietary factors include the intake of calcium and vitamin D, selenium and vitamin B6 – deficiencies in one or more of these nutrients have been associated with an increased risk of polyp formation and possibly cancer. Calcium and vitamin D can be obtained through diet; however, a large number of Americans may not be consuming enough calcium or vitamin D, particularly those that are either under restrictive diets, such as lactose free diet, a gluten-free diet, or do not have enough sun exposure.
There is solid evidence to support that increasing calcium and vitamin D intake may reduce the development of colorectal polyps and cancer. Other tangible benefits to maintaining adequate nutrition include a possible reduction in bone loss (osteoporosis), or other cancers, such as prostate cancer. Studies also support a possible benefit to selenium and vitamin B6 intake in regards to the prevention of colorectal cancer.
One key factor in the effectiveness of a vitamin or mineral in the form of a supplement is how well it is absorbed. Absorption is influenced by how much of the elemental form of the vitamin is present in the supplement and what the element is compounded with. Dietary calcium is generally the best way to absorb calcium. Some people may not be able to consume enough calcium, such as those with lactose intolerance. Calcium carbonate, the most popular form of calcium, such as in Tums, has high elemental calcium at 40%. Unfortunately, calcium carbonate is poorly absorbed and is greatly affected by food intake--only about 4 percent is absorbed. Calcium citrate, on the other had, has less elemental calcium at 21%, but has much higher absorption and is not so greatly affected by food intake or acid reducing medications. Additionally, the amount of calcium absorbed depends on the total amount of elemental calcium consumed at one time. As the amount increases, the percentage absorption decreases. Absorption is highest in doses 500 mg. So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day. All information regarding minerals and vitamins, including what they are compounded with and how well they are absorbed, is documented on the web at http://dietary-supplements.info.nih.gov/, an official site of the National Institutes of Health.
Vitamin D also comes in various forms. Vitamin D level is now routinely measured by a blood test. A deficiency of vitamin D is associated with colorectal cancer, prostate cancer and osteoporosis. However, vitamin D deficiency can also make someone feel lethargic, fatigued, or weak. Here the form of the vitamin is important. Vitamin D3 (cholecalciferol) is the most active form of the medication in the intestine and blood. However, ergocalciferol (vitamin D2) is traditionally the most widely supplied form of the vitamin.
The goal of vitamin supplementation is to reach a normal steady state of the vitamin in your body and blood. Evidence does not support consuming amounts greater than recommended daily allowance (RDA) or raising blood levels beyond median range. So, aiming to raise low vitamin levels into the average normal range should be the goal.
Colorectal cancer is the only cancer that has shown a decreasing incidence of cancer death. This is due to multiple factors such as early detection through colonoscopy and better surgical and medical treatment. Further improvements in the understanding of the triggers for colorectal cancer, including genetic factors and dietary or social factors, will lead to additional advances in the prevention, detection and treatment of this disease. Ensuring that our patients have a normal amount of calcium and vitamin D as well as selenium and vitamin B6 is an important goal for overall colon health.
Dr. Lustberg, January 2010
Introduction