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One childhood memory that stands out for me is when my mother arrived home with a new bottle of cod-liver oil. The morning ritual consisted of trying to get mom distracted so she would forget the tablespoon of cod-liver oil. Today, it seems that source of Vitamin D is taking on new importance once again.
Vitamin D is a prohormone, which means that our bodies covert it to various hormones integral to keeping us in peak shape. New studies suggest that Canadians may not be getting enough of this vital substance. It also appears that adequate levels may help prevent breast and colon cancer.
Vitamin D is produced in our skin by a reaction requiring sunshine having a UVB index over 3. In the northern hemisphere, getting enough exposure to the sun can be a real problem. Since this process takes place deep in the skin, persons with dark skin containing lots of melatonin require more sunlight. When an active form is needed, the liver or kidney convert it into the active hormone called 1,25-D or calcitriol. When active, it circulates around and binds to a receptor within the nucleus of certain cells. It is instrumental in the absorption of calcium and the constant rebuilding and remodeling of our bones that goes on daily. It has been shown to be able to repair radiation damage, and influence how our immune system works, with implications to things such as heart disease, diabetes and dementia. In animal studies, it was shown to be able to promote killer cells into action shrinking some tumors which have Vitamin D receptors in their cells.
When your Vitamin D levels drop, calcium cannnot get into the bones where it is needed. Bones get thinner and osteoporosis is possible. Populations with low Vitamin D levels tend to have higher blood pressures, and respond to inflammation poorly. Calcium and Vitamin D are in tight control in our bodies by small glands in our necks called parathyroid glands. Too much Vitamin D can result in kidney stones, headaches and fatigue.
So, what is the real deal with the sun? The problem stems from the sunlight itself which is a mixture of energy carried at different frequencies - some good and some strong enough to do damage. You can tell if you are deficient by measuring levels of calcidiol in your blood, but the test is rather costly to the system. Extreme deficiency produces a disease of bone deformity called Rickets. But how much is enough?
There is a push to revise what the normal levels are in our system. Cod liver oil is the highest food source of Vitamin D. Other good food sources include tuna, sardines and herring. Calcium supplements routinely contain Vitamin D. Adequate daily intake of Vitamin D is 200 IU (5 micrograms), but those who are low should aim for supplementation well over 1000 IU. Sunlight is still our best way to get your Vitamin D. I am a big proponent of walking, especially when it is sunny. I encourage people to build more walking into their day, whether it is running an errand or just for recreation. Supplements are a reasonable alternative too. See you on the sidewalk!
Related resources:
● 15 Health Benefits of Vitamin D, According to Science (+15 Best Vitamin D Foods) from Jen Reviews.
● What are the Vitamin D Side Effects? You Might be Surprised ... from Easy Immune Health.
● Vitamin D from Wikipedia, the free encyclopedia.
● Dietary Supplement Fact Sheet: Vitamin D from Office of Dietary Supplements, National Institutes of Health (NIH).
● Vitamin D: Boning up on the sunshine vitamin from IN DEPTH
Health, CBC News.
● Vitamin D : Recommendations and Review Status from Health Canada. What Is Vitamin D?
What Are DRIs? "Dietary Reference Intakes (DRIs) are a comprehensive set of nutrient reference values for healthy populations established by Canadian and American scientists."
What Are the DRIs for Vitamin D? "The Adequate Intake (AI) values for vitamin D, as currently expressed in the DRI tables, are as follows:
0-1 year: 200 IU per day
2 -50 years: 200 IU per day
51-70 years: 400 IU per day
> 70 years: 600 IU per day
The Tolerable Upper Level of Intake (UL) for vitamin D for one year old and over is 2000 IU per day."
● Are You Getting Enough Vitamin D? By Kathleen M. Zelman, MPH, RD, LD, WebMD, Reviewed by Brunilda Nazario, MD.
● The Miracle of Vitamin D by Krispin, Sullivan, Krispin, Consumer Health Organization of Canada.
● Vitamin D Casts Cancer Prevention in New Light by Martin Mittelstaedt, Globe and Mail [Toronto].
● Vitamin D from American Cancer Society. "Vitamin D is an essential vitamin the body needs to regulate the amount of calcium and phosphorus in the body. Other common name(s): the sunshine vitamin, calcitriol, calciferol, ergocalciferol (vitamin D2), cholecalciferol (vitamin D3), 1,25-D. Scientific/medical name(s): 1,25 dihydroxycholecalciferol; 1,25 dihydroxyvitamin D."
● Vitamin D from MayoClinic. "Vitamin D is found in many dietary sources such as fish, eggs, fortified milk, and cod liver oil ... vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), cancer, and several autoimmune diseases ... Rickets and osteomalacia are classic vitamin D deficiency diseases."
● What foods contain vitamin D? "There are only a few food sources of vitamin D. Good sources of vitamin D are fortified foods and beverages like milk, soy drinks, and margarine ... Fish, liver, and egg yolk are the only foods that naturally contain vitamin D.
● Vitamin D from MedlinePlus. "Vitamin D is a fat-soluble vitamin that helps the body absorb calcium. Fat-soluble vitamins are stored in the body's fatty tissue ... Vitamin D is found in the following foods: Cheese, Butter, Cream, Fortified milk (all milk in the U.S. is fortified with vitamin D), Fish, Oysters, Fortified cereals, Margarine ... Vitamin D deficiency can lead to osteoporosis in adults or rickets in children. Too much vitamin D can make the intestines absorb too much calcium. This may cause high levels of calcium in the blood. High blood calcium can lead to calcium deposits in soft tissues such as the heart and lungs. This can reduce their ability to function. Kidney stones, vomiting, and muscle weakness may also occur if you have too much vitamin D."