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Exceeding this dose will cause poisoning! What is the safe upper limit of vitamin D?
Vitamin D is an essential nutrient that supports human health, but overdose can cause health problems, including poisoning. According to existing research, the normal range of vitamin D is that in adult blood, the concentration of 25-hydroxyvitamin D should be between 20 and 50 nanograms per milliliter (ng/mL). If the concentration exceeds 150 ng/mL, adverse effects may occur.
"The Endocrine Society recommends a safe upper limit of 100 ng/mL."
The main risk of overdose of vitamin D is high blood calcium concentrations, which can lead to abnormal calcification of bones, soft tissues, heart and kidneys. In addition, high blood pressure is a potential complication. When overdose is taken, symptoms of vitamin D poisoning may include dehydration, vomiting, diarrhea, loss of appetite, irritability, constipation, fatigue and muscle weakness. Symptoms usually appear several months after overdose.
"In almost all cases, complete recovery can be achieved within a month with a low-calcium diet and steroid drugs."
Some symptoms of vitamin D overdose may also be caused by vitamin K deficiency. Some studies have shown that co-ingestion of vitamin K can reduce the negative effects of vitamin D, but this result has not yet been tested in humans.
Safe intake limits of vitamin D
To protect people from the toxicity of vitamin D, the National Academy of Medicine has established a Tolerable Upper Intake Level (UL). These recommended daily amounts vary based on age and gender:
- 0–6 months: 25 mcg (1000 IU)
- 7–12 months: 38 mcg (1500 IU)
- 1–3 years: 63 mcg (2500 IU)
- 4–8 years: 75 mcg (3000 IU)
- 9 years and older: 100 mcg (4000 IU)
- Pregnant and lactating women: 100 micrograms (4000 IU)
"Excessive intake of vitamin D has been observed at levels of 1,925 micrograms (77,000 IU) per day."
In the case of acute overdose, it may take days to months to cause poisoning at doses ranging from 15,000 mcg (600,000 IU) to 42,000 mcg (1,680,000 IU).
Effects of long-term intake of vitamin D
Overexposure to sunlight does not cause vitamin D poisoning because the body regulates its production. Under UV exposure, vitamin D precursors in the skin reach equilibrium and any further vitamin D produced is broken down. This process is less effective in skin with abundant melanin.
"Endogenously produced vitamin D3 is mainly transported through vitamin D transport protein, but it does not easily enter the plasma."
Oral supplementation of vitamin D will quickly reach the liver and increase calcifediol in the plasma. In this regard, long-term supplementation of vitamin D may cause a lot of controversy, especially whether the requirements for vitamin D are consistent among different ethnic groups.
Relevance of cardiovascular disease
There is evidence that dietary vitamin D may be transported by lipoprotein particles to cells in the arterial wall and into atherosclerotic plaques, where it may be converted into an active form, which raises the question of the role of vitamin D in atherosclerotic plaques. The impact of sclerosing calcification and cardiovascular risk has been questioned.
"Active vitamin D levels are inversely related to coronary artery calcification."
The vitamin D needs of different ethnic groups may be affected by the interaction between genetic factors and environmental influences, so it is not appropriate to generalize. In some sun-exposed areas, vitamin D levels in people's bodies still fail to reach normal standards, which shows the importance of vitamin D supplementation from a public health perspective.
Consideration of ethnic differences
Differences in physiological pathways between ethnic groups, particularly due to the influence of skin melanin, may prevent vitamin D intake recommendations from being universal. Some studies have found that vitamin D concentrations in some groups do not increase significantly even when exposed to sunlight.
This has led people to think about a question: How to evaluate the needs and safe upper limits of vitamin D among different ethnic groups to avoid unnecessary health risks?
