Individuals taking lower doses of vitamin D developed COVID at double the rate as those taking vitamin D in higher doses
Vitamin D plays a role in bone growth and remodeling, also supporting functions related to immunity and glucose metabolism while assisting with the reduction of inflammation. The Office of Dietary Supplements indicates that the recommended dietary allowance (RDA) of this vitamin is 15 mcg (600 IU) per day for most adults, increasing to 20 mcg (800 IU) daily for those aged 70 and up, but existing and new research is showing vitamin D in higher doses is safe and effective for fighting viruses and other ailments.
Many dietary supplements contain much higher amounts of vitamin D. According to research this is safe, and, in fact, taking vitamin D in higher doses may be especially beneficial for certain individuals.
Vitamin D intake safety
A 2017 study published in Dermato Endocrinology collected base data from 3,882 participants, then conducted follow-up between six and 18 months later — after participants took supplements containing between 1,000 and 15,000 IU of vitamin D per day. Supplementing with these higher doses did not result in toxicity for the subjects in the study, nor did it negatively affect their body’s ability to regulate calcium stability.
Researchers further reported that having a serum blood level of vitamin D of up to 300 nmol/L was found to be safe. Additionally, vitamin D intakes well above the RDA were often required to achieve serum blood levels of 100 nmol/L or higher. This is important because other studies note that the optimal serum levels of this vitamin are between 100 nmol/L and 130 nmol/L.
Individuals who may benefit from vitamin D in higher doses
Results from the 2017 study suggest that while most people can benefit from vitamin D in higher doses, exceeding the RDA may be even more important for individuals with an above-normal body mass index (BMI).
In the study, the average vitamin D intake needed to achieve a blood serum level of 100 nmol/L or higher was 6,000 IU per day for individuals with a normal BMI. However, individuals categorized as being overweight required vitamin D intakes of 7,000 IU per day to reach this level, and those considered obese needed 8,000 IU of vitamin D daily to achieve the same effect.
Higher blood serum levels of vitamin D may also provide health benefits for certain individuals, such as females entering menopause. In a 2019 study published in the journal Aging, researchers found that for every 5 nmol/L increase in blood vitamin D levels, breast cancer risk for pre-menopausal women decreased by 6%. This benefit was even greater for women of Asian descent.
Another study, this one published in Nutrients in January 2022, looked at vitamin D in higher doses and its effect on the COVID-19 virus. In this case, health care workers took vitamin D3 supplements, some starting at 50,000 IU per day for two weeks before transitioning to 5,000 IU daily, and the remaining subjects taking a consistent daily dose of 2,000 IU.
Individuals taking lower doses of vitamin D developed COVID at double the rate as those taking vitamin D in higher doses. Approximately one-half of low-dose subjects also experienced mild symptoms, while one in four of the high-dose subjects were asymptomatic. Researchers added that while all study subjects increased their blood serum levels after supplementing with vitamin D, only those taking 5,000 IU per day had these levels normalize.
Who should avoid higher vitamin D doses
Individuals who are hypersensitive to vitamin D should not take higher doses. Hypersensitivity can lead to an inability to regulate vitamin D metabolism and, according to research, can result in toxicity. It may even create issues when this vitamin is taken in amounts that are often considered safe for the general population.
Toxicity can also be a concern for individuals with congenital disorders such as Williams-Beuren syndrome, those with granulomatous disorders, and some types of lymphomas. Symptoms of vitamin D toxicity include abdominal pain, recurrent vomiting, confusion, apathy, excessive thirst or urination (polydipsia and polyuria, respectively), and dehydration.