March 2010 Archives

Multiple factors influence vitamin D levels

Vitamin D is produced in the body via sunlight. It is also obtained from foods such as oily fish (salmon, mackerel, sardines), fortified milk, cereals, and from supplements. Low vitamin D levels may be caused by a lack of sun exposure, lack of dietary vitamin D, malabsorption, side effects from medications or supplements, chronic diseases such as kidney or liver disease, and other causes. In addition, seniors, infants and toddlers, dark-skinned people, and pregnant or breastfeeding women may be particularly at risk for low vitamin D levels. Now, we are discovering there are other factors that may affect vitamin D levels.

The new study explored the importance of skin pigmentation, total cholesterol, and baseline blood levels of vitamin D (measured as 25- hydroxy vitamin D) on vitamin D production after ultraviolet B (UVB) exposure. Participants in this study had four UVB exposures several days apart to the chest and back, and each exposure was equivalent to about 30 minutes of sun exposure in the middle of a clear summer day in Denmark. Results showed:

• Of the 182 participants screened for baseline vitamin D, 67% were considered vitamin D insufficient and 18% were vitamin D deficient

• Baseline levels of vitamin D were higher in people who ate fish at least once a week

• Among a group of 50 participants, researchers found significantly higher vitamin D production after UVB exposure in participants with a low baseline vitamin D level compared with those with a higher baseline level

• Fair-skinned and dark-skinned people had similar increases in vitamin D levels after UVB exposure

• There is an association between total cholesterol and vitamin D production, and a low cholesterol level might hinder vitamin D production

Checking vitamin D levels

Here are some tips regarding vitamin D levels:

Talk with a doctor. A healthcare professional can help you decide whether or not it is important to check your vitamin D level. People who live in areas with little sunlight or who are at risk or suffering from chronic diseases such as cardiovascular disease or cancer may especially want to discuss the topic of vitamin D with a doctor.

Be careful with sun exposure. Many physicians recommend brief amounts of time (less than 15 minutes a day) of sun exposure for general health, but studies have shown that sun exposure may not be enough to raise vitamin D levels that are low. Further, excess sun can increase the risk of skin cancer, and the authors of this study do not recommend UVB treatment for low vitamin D levels for that reason. Instead they recommend treating low vitamin D levels with vitamin D supplements. Talk with your doctor about treatment strategies for low vitamin D levels.

(J Invest Dermatol 2010;130: 546-53)

• Talk with a professional. Being overweight increases a person's risk of a number of medical conditions such as type 2 diabetes, high blood pressure, and high cholesterol. If you are overweight, talk with a knowledgeable doctor to come up with a good program for you, and work with a nutritionist who can educate you about what to eat and help you stay motivated and on track for a healthy weight. As this study showed, people who attended more dietary counseling sessions lost greater amounts of weight than those who attended less.

• Identify triggers that lead to cravings or overeating. It is important to ask yourself questions such as "Why do I choose foods that are not healthy for me?" and "What feelings or circumstances lead me to crave unhealthy foods or to overeat?" Answering such questions can help you learn how to manage the cravings and feelings that lead to overeating, and help you plan ahead with healthier alternatives in situations where you might normally make unhealthy choices.

• Choose the right foods. You know the recommendations by now, but have you taken specific steps to improve your diet? The body needs an abundance of fruits and veggies--at least 5 servings every day--and a source of protein every day in order to optimize health and prevent disease. Eating foods high in sugar increases cravings, so reach for low-sugar, low-fat, nutrient-dense foods when eating regular meals and when snacking.

• Plan ahead. Sit down and plan your meals for the week. Try grocery shopping on a Sunday in order to stock the refrigerator with healthy foods to get you through the week. Don't bring high-sugar, high-fat foods into the house, which may increase the temptation for overeating, but keep looking for healthy foods that you really enjoy so you have options if a snack attack hits.

• Exercise regularly. Guidelines recommend 60 minutes of exercise every day for healthy adults and 90 minutes for children. Exercise helps reduce cravings and overeating and also improves risk factors for chronic disease such as high blood pressure, glucose and cholesterol levels. If the optimal amount is too overwhelming either because of your schedule or fitness level, remember that everything helps. Get the all-clear from your doctor, and then start slowly and build over time. As your fitness improves, you will naturally enjoy longer exercise sessions, rather than slogging through. Exercise buddies and cross-training are also good tricks for keeping yourself going.

Genes are not destiny

To study diabetes risk, researchers enrolled 5,535 healthy British men and women, with an average age of 49 years into a study. After following these people for 10 years, 302 of them developed type 2 diabetes.

The researchers studied how well the Cambridge and Framingham risk scores predicted who developed diabetes in the group. They also looked at how 20 genetic changes that increase diabetes risk affected the ability to predict type 2 diabetes risk in the group.

Adding the genes to the risk scores did not significantly improve the ability to determine who would develop diabetes. In other words age, gender, family history of diabetes, body weight, smoking, and blood levels of cholesterol, triglycerides, and blood sugar are more effective for determining diabetes risk than genes.

You have the power to defeat diabetes

The most exciting thing about this study is that it tells us that we each have the power to positively affect our own health. Two important factors that affect diabetes risk--body weight and smoking--are within our control. By maintaining a healthy body weight and not smoking, we can lessen the chances that we develop diabetes, even if we have "diabetes genes."

You can't change your family medical history, age, or gender, but you can make your health a priority starting today. A healthy diet and regular exercise will keep obesity at bay and reduce diabetes risk.

(BMJ 2010;340:b4838. doi:10.1136/bmj.b4838; National Diabetes Information Clearinghouse. National Diabetes Statistics, 2007. Accessed February 13, 2010. Available: http://diabetes.niddk.nih.gov/DM/PUBS/statistics/#allages)