01 Oct Vitamin D- an Undervalued Nutrient
In light of newly released research, and as the weather changes and we spend less time outdoors, this month’s newsletter focuses on Vitamin D. Many individuals (especially those living in North Eastern climates) are deficient in this nutrient which scientific research is showing to be very important and highly undervalued.
Vitamin D is a fat soluble vitamin which is found in a few foods but is also made by our bodies in response to sunlight. Whether ingested or synthesized in the skin, Vitamin D is converted to its most active form within the liver and kidneys.
Why is Vitamin D important?
Vitamin D acts as a hormone in that it sends messages to the intestines to increase absorption of the minerals calcium and phosphorous. It also decreases urinary excretion of calcium. It works with other nutrients and hormones to promote bone mineralization. Most of us know that calcium is of paramount importance in bone health. (For a more complete review of the importance of calcium throughout the body, please see my Newsletter dated September 2006: Got Calcium?). Without Vitamin D, calcium is poorly absorbed and bones become brittle and misshapen.
In addition to its importance in bone health, new research is showing that Vitamin D is essential for maintaining a health immune system. It also plays a role in forming blood cells. In addition, it may play a role in insulin (and therefore blood sugar) regulation as is evidenced by the fact that Vitamin D receptors have been discovered in the area of the pancreas responsible for insulin production. Lastly, new data is shedding light on the role of Vitamin D in regulating cell growth and differentiation; a process which may reduce the risk of cancer.
What are the sources of Vitamin D?
Fatty fish are the best sources of Vitamin D (these include salmon, mackerel, tuna, sardines, herring, and cod liver oil). Eggs are another good source. Milk (cow’s milk and most brands of soy and rice milk) and cereal are often fortified with Vitamin D. But note that dairy products such as yogurt and cheese are generally not made with Vitamin D-fortified milk.
Sun exposure is the most important source of Vitamin D. Vitamin D synthesis in the skin requires direct contact with UV rays. This means that the season, time of day, cloud cover and shade, smog, geographic latitude, and use of sunscreen (with an SPF of 8 or greater) all affect Vitamin D synthesis. I recommend exposure of 10-15 minutes at least twice a week to the face, arms, hands or back without sunscreen on a clear day as a good way to get Vitamin D (and enjoy the outdoors!). Keep in mind that risk of sun damage to the skin should always be balanced with need for Vitamin D; protect yourself adequately
after you’ve had your 15 minutes in the sun and, if you have a history of skin cancer, you should avoid this unprotected sun exposure completely.
Who is likely to be deficient?
At least one in seven adults has been reported deficient in Vitamin D. This has certainly been my experience in my practice. Whether conducting a dietary analysis or laboratory testing, I often find undetected deficiencies in my patients. There are populations who are specifically susceptible to deficiency states. These include:
People who have limited exposure to sunlight or live in polluted areas (perhaps a significant number of people living here in the North East) may suffer Vitamin D deficiency.
In addition, strict vegetarians may be at risk since fish and eggs are the best dietary sources.
Those with darkly pigmented skin have higher melanin content in their skin, reducing the skin’s ability to produce Vitamin D.
Those with a fat malabsorption problem (such as pancreatic enzyme deficiencies, Crohn’s disease, Cystic Fibrosis, Celiac Disease, or surgical removal of part of the stomach or intestines) may require supplementation.
Vitamin D deficiency is also common in those with hyperthyroidism, especially women, and in those with hyperparathyroidism.
Those with liver or kidney disease are not able to convert Vitamin D to its most active form and require supplementation of Vitamin D in that form (1, 25- dihydroxyvitamin D).
Unfortunately, breast milk is not a good source of Vitamin D. The American Association of Pediatrics recommends supplementing exclusively breastfed infants beginning within the first 2 months of life.
The skin’s ability to synthesize Vitamin D and the kidney’s ability to convert it to its active form both decline with age. I recommend that all of my patients, but particularly those of middle age and older get tested for Vitamin D 3 levels.
Note that high caffeine intake (from coffee, tea, chocolate, and some carbonated beverages) may inhibit Vitamin D receptors and has been linked to lowered bone mineral density.
Also, some medications may decrease Vitamin D. These include: antacids, calcium-channel blockers (used to treat high blood pressure and heart conditions), cholestyramine (a cholesterol-lowering medication), some anticonvulsants, and mineral oil.
How much is enough:
The “Adequate Intake” for Vitamin D developed by the Institute Of Medicine (IOM) is a value of between 200 and 600IU a day, with requirements increasing with age. Many medical practitioners argue for far higher intake, as high as 10,000 IU a day. That being said, food consumption studies suggest that current intakes for the general population are far lower than even the values set by the IOM.
When is supplementation important?
I generally recommend boosting dietary intake and moderate sun exposure to all of my patients. I reserve supplementation for those clearly deficient or at risk of deficiency and those with a condition which responds positively to supplementation. Such conditions include:
– Osteoporosis, osteopenia, or those at risk (for example, those taking steroids such as prednisone)
– Osteomalacia and rickets (softening of the bone due to improper mineralization)
– Cancer or strong risk factors for cancer, particularly of the breast or colon
– Those with a strong family history of type 1 diabetes (supplementation is protective)
– Those with high blood pressure or heart disease who have low blood levels may benefit from supplementation
– Those with osteoarthritis who have low blood levels of Vitamin D may also benefit
– Patients with musculoskeletal pain and migraines should be tested for Vitamin D levels. If deficient, Vitamin D and calcium may improve these conditions.
– Multiple Sclerosis occurs more often in areas of little sun exposure. There is some evidence to suggest it may be helpful in the treatment of this disorder.
– Topical Vitamin D preparations may be effective in skin conditions such as psoriasis and vitiligo.
– Research shows that Seasonal Affective Disorder can be alleviated through the use of Vitamin D.
How much is too much?
Vitamin D toxicity has been reported in rare cases. Those with hypersensitivity to Vitamin D (such as hyperparathyroidism, hypercalcemia, some forms of lymphoma, or sarcoidosis) may be particularly susceptible to toxicity symptoms such as loss of appetite, nausea, vomiting, constipation, weakness, weight loss, excessive thirst and increased urination. Toxic doses of Vitamin D can also increase blood levels of calcium causing mental changes (such as confusion), heart arrhythmias, and deposits of calcium in the body (such as kidney stones). The large majority of published cases of toxicity have occurred at levels of intake above 40,000 IU per day.
Should you supplement with Vitamin D?
I recommend that many of my patients request Vitamin D testing (25-OH-Vitamin D is the most accurate indicator) from their physicians. This is particularly true during the winter months and in those who do not get enough sun exposure or who have other risks for deficiency. If your test results reveal low levels, you should increase your consumption of foods containing Vitamin D. You should also aim to increase your sun exposure to 15 minutes a few times a week. Supplementing with about 1000IU a day in an adult for a few months will likely be all that’s needed to increase your serum levels.
Have your physician check both calcium and Vitamin D levels again to ensure your levels have stabilized.
Vitamin D supplementation at high levels should be monitored by a physician. Supplementing with Vitamin D3 is more effective and carries potential for fewer side effects than Vitamin D2.
Get outside while the weather is still great… A fish barbeque on the deck would be a fantastic idea! (And, if you can, have a doctor or naturopath assess your Vitamin D intake and blood levels).
Please Note: This information is for educational purposes only. Consultation with a licensed health care practitioner is recommended for anyone suffering from a health ailment. You are free to use the information in this newsletter or pass it on to others, but please keep it intact and credit it to Dr. Leat Kuzniar, ND.