Recent research reveals that vitamin D deficiency is strongly linked to increased death in adults, and is particularly associated with diabetes-related deaths. These findings are especially worrisome for black people who are disproportionately affected by vitamin D deficiency and type 2 diabetes.
Vitamin D is often referred to as the “sunshine” vitamin because it can be made in the skin after exposure to sunlight. Vitamin D deficiency is primarily attributed to lifestyle and environmental factors that reduce exposure to sunlight. However, black people are at increased risk of vitamin D deficiency because of pigmentation. Dark skin tone can reduce vitamin D production in the skin by over 90 percent. There is also evidence that links vitamin D deficiency to reduced insulin secretion and insulin sensitivity, which are risk factors for type 2 diabetes.
How Much Vitamin D Do You Need?
The amount of vitamin D you need each day depends on your age. Recommended intake for adults between the age of 19 – 70 years is 600 International Units (IU) daily.
Very few foods naturally have vitamin D. Fatty fish such as salmon, tuna, and mackerel are among the best sources. Beef liver, cheese, and egg yolks provide small amounts. Fortified foods provide most of the vitamin D in American diets. Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart, and so are many of the plant-based alternatives such as soy milk, almond milk, and oat milk. But foods made from milk, like cheese and ice cream, are usually not fortified. Vitamin D is also added to many breakfast cereals and some brands of orange juice, yogurt, and margarine.
The best measure of one’s vitamin D status is blood levels of 25-hydroxyvitamin D. In general, levels below 30 nmol/L are too low for overall health, and levels above 125 nmol/L are probably too high. Levels of 50 nmol/L or above are sufficient for most people. Blacks tend to have the lowest levels and whites the highest levels of vitamin D.
The study, referenced above, found that vitamin D levels of 10 nmol/L or less were associated with 2-3 times higher risk of death, with the largest effect being observed in patients aged 45 to 60 years. Levels of 90 nmol/L or higher were associated with a 30-40% reduction in death, again with the largest effect being found in the 45 to 60-years-old age group.
Can vitamin D be harmful?
When amounts of vitamin D in the blood become too high, it causes toxicity. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. Too much vitamin D can also raise blood levels of calcium, causing confusion, disorientation, and problems with heart rhythm. Excess vitamin D can also damage the kidneys.
Vitamin D toxicity almost always occurs from the overuse of supplements. Excessive sun exposure doesn’t cause vitamin D poisoning because the body limits the amount of this vitamin it produces.
Vitamin D Test
If you are black and have type 2 diabetes, you are at increased risk of vitamin D deficiency. Not sure if you’re getting enough or too much vitamin D? Talk to your health care provider about a blood test to determine your vitamin D levels.
An award-winning registered dietitian, certified diabetes educator, and former spokesperson for the Academy of Nutrition and Dietetics, is the author of the Diabetes Guide to Enjoying Foods of the World; The African American Guide to Living Well With Diabetes.