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We Asked a Dietitian Why Vitamin D Supplements Can Make You Feel Worse
Millions of Americans experience vitamin D deficiency, leading many to turn to supplements in an effort to improve their health. However, reports have surfaced of individuals feeling *worse* after starting vitamin D supplementation. To understand this counterintuitive reaction, a registered dietitian at Lebanon Valley College, Morgan L. Walker, MS, RD, sheds light on the potential causes.
Why Vitamin D Supplements Can Cause Adverse Effects
Walker explains that vitamin D is a fat-soluble vitamin crucial for regulating calcium in the body. One common reason people feel unwell after taking vitamin D is that excess amounts can raise blood calcium levels, a condition known as hypercalcemia. Here’s more likely with high doses taken over time, but some individuals may be sensitive even to moderate amounts.
Certain individuals are particularly vulnerable to adverse effects, including those with kidney disease or disorders that affect vitamin D metabolism. Symptoms of elevated calcium can range from nausea, constipation, and fatigue to muscle weakness, headaches, increased thirst and urination, and a general feeling of being “foggy.” In severe cases, heart rhythm changes or kidney problems can occur.
Beyond Calcium: Other Potential Contributors
The issue isn’t always about too much vitamin D directly. Nutrient deficiencies, particularly magnesium, can also play a role. Magnesium is essential for activating and utilizing vitamin D, and low levels can exacerbate symptoms like fatigue, muscle cramps, headaches, and sleep disturbances as vitamin D supplementation increases demand. Some individuals may experience intolerance to ingredients within the supplement itself, such as carrier oils like soybean, coconut, or corn oil.
How Much Vitamin D Is Too Much?
The general tolerable upper intake level for vitamin D is 4,000 IU per day, though adverse effects can still occur at lower amounts for some people.
What Should You Do If You Feel Worse?
If you experience negative symptoms after starting vitamin D supplementation, the recommended course of action is to temporarily stop taking the supplement and consult with a healthcare professional. Blood tests, including measurements of 25-hydroxyvitamin D, calcium, and kidney function, can help determine if levels are too high or if another underlying issue is present. Walker emphasizes that vitamin D is safest when dosage is individualized based on lab values, rather than self-treating with high doses.
Frequently Asked Questions
Why does vitamin D affect calcium levels?
Vitamin D helps regulate calcium in the body, and excess vitamin D can raise blood calcium levels, leading to hypercalcemia.
Who is more likely to experience negative effects from vitamin D supplements?
Individuals with kidney disease or disorders that alter vitamin D metabolism may be more sensitive to the effects of vitamin D supplements.
What symptoms might indicate a problem with vitamin D supplementation?
Symptoms can include nausea, constipation, fatigue, muscle weakness, headaches, increased thirst and urination, or feeling “foggy.”
Given the potential for both deficiency and adverse effects, how carefully do you consider your individual health needs before starting any new supplement regimen?