A Word from Dr

A Word from Dr. Pfenninger About…Vitamin D

The definition of a vitamin is “an element that the body cannot make and that must be consumed or obtained from other sources”. Vitamins A, D, E and K are fat-soluble, which means they are stored in the fat. Because of this, it is more likely that a person can accumulate toxic levels. Consequently, for all the fat-soluble vitamins (versus the water-soluble, like C and the B vitamins) there has always been a caution about consuming too much. However, there is some new thinking and research going on regarding Vitamin D.

My mother told me that when I was young I was diagnosed with rickets. Rickets is a disease in children who have a deficiency of Vitamin D. Bones do not develop correctly, and the mere handling of children can cause them pain. I was being fed on a formula that consisted of corn syrup and cow’s milk – common in those days. Once Vitamin D was added to my diet, my condition resolved. Because rickets was so common in the past, Vitamin D is now routinely added to milk. Many cereals are also supplemented. This has virtually eliminated rickets in the United States.

In adults, Vitamin D continues to be essential for bone health. With aging, not only is the diet more likely to be deficient in Vitamin D, but the absorption process is less efficient. As anyone with osteoporosis knows, when calcium supplements are recommended, Vitamin D is also advised. Many calcium supplements already contain Vitamin D. Without Vitamin D the body cannot absorb calcium from food or supplements no matter how much calcium is consumed. When the blood levels of calcium are low, the body will produce hormones that dissolve the calcium from bone so that circulating calcium levels are adequate. Thus, the bones become very thin and have a tendency to fracture.

New research has revealed many other functions for Vitamin D. Studies show that low intake of the vitamin has been associated with numerous cancers including bladder, esophageal, rectal, colon, cervical, Hodgkins, and others. It may also be associated with prostate cancer. On the other hand, an adequate level of Vitamin D appears to reduce heart disease and lower blood pressure. Multiple sclerosis and diabetes seem to be lessened with higher levels of Vitamin D intake. A reduction in rheumatoid arthritis and gingivitis (gum disease), and improvement of the immune system have also been noted.

USDA Guidelines suggest RDAs (recommended daily allowances) for the various vitamins. From birth to 50 years of age, 200 international units (IU) daily are recommended. From 51 to 70, it is 400 IU, and after 70 it is 600 IU. Remember, these guidelines are based on what is needed to prevent problems caused by too little of the vitamin (Rickets, osteoporosis, etc.). Many experts wonder if increasing the daily amounts wouldn’t actually prevent other diseases like those mentioned above. Most researchers feel that when the new RDA Guidelines are published in 2008, the RDA for Vitamin D will be at least 1000 IU. That amount is certainly safe for everyone. Even 2000 IU have not been shown to cause a problem, but “more” is not necessarily always “better”.

Excessive Vitamin D can cause nausea, vomiting, loss of appetite, and constipation. It can cause heart and kidney damage. It must be used with caution when antacids containing magnesium are used concurrently. When used with a diuretic, it could cause excessive calcium absorption, also leading to kidney problems. Doses over 2000 IU have been reported to cause toxic symptoms in some people.

In addition to diet, Vitamin D is also made when the body is exposed to UVB light. This same UVB light is also responsible for various skin cancers, however. If you use sunscreens, the benefit of the sun in producing Vitamin D is blocked. But, as little as 15 to 30 minutes per day in the sunshine will produce enough Vitamin D to be beneficial for the body. The body will not make excessive Vitamin D with more exposure to the sun. However, in northern climates like ours, think of how little time most of us spend outside. In the summer, it is too hot so we stay inside with the air conditioning. In the winter it is too cold and we are all wrapped up when we go outdoors and are very minimally exposed to the sun. Small children, as well the elderly who may be in assisted living or nursing homes, rarely receive enough sun exposure.

Dietary sources then are the main source for Vitamin D. We already mentioned Vitamin D supplemented milk and cereals. Cod liver oil (1360 IU per tablespoon) is extremely high in calcium and Omega 3’s (another desirable element). Salmon, mackerel, tuna in oil, and sardines in oil, all have about 300 IU -per serving. One cup of fortified milk has 100 IU of Vitamin D. On average, a daily multi-vitamin supplement contains 400 IU.

When calculating how much Vitamin D is being consumed, all foods must be considered. The importance of Vitamin D is being clarified through on-going research. It appears to be much more valuable than just preserving bone health. Current RDA recommendations may be too low, and an optimal level and an upper safe level of intake still are unknown.