Vitamin A is a vital nutrient that supports the body’s development and strengthens the immune system. Because our bodies do not naturally produce vitamin A, some choose to take supplements. However, too much vitamin A is likely to harm bone health, researchers warn.
Normally, we derive vitamin A form the food we eat, such as carrots, sweet potatoes, beef liver, salmon, and several dairy products. How much vitamin A someone needs depends on their age, as well as other factors. The National Institutes of Health (NIH) state that the ideal daily intake of vitamin A is 900 micrograms retinol activity equivalents for men and 700 mcg RAE for women aged 19-50.
Over time, supplementation of vitamin A might lead to an overload of this nutrient, which can actually increase a person’s risk of experiencing bone fractures. Researchers from the Sahlgrenska Academy at the University of Gothenburg in Sweden reported in the Journal of Endocrinology that taking too much vitamin A can make bones “thin out,” thereby putting them at risk of fracturing easy.
Dr. Ulf Lerner and team administered doses of vitamin A the equivalent of 4.5-13 times the RDA for humans – for 1, 4, or 10 weeks. The scientists saw that after only 8 days of oversupplementation, the mice’s bone thickness had started to decrease. Over 10 weeks, the rodents’ bones became increasingly fragile and prone to fracturing.
“Overdose of vitamin A could be increasing the risk of bone-weakening disorders in humans but more studies are needed to investigate this. In a majority of cases, a balanced diet is perfectly sufficient to maintain the body’s nutritional needs for vitamin A.” – Dr. Ulf Lerner
Most supplements on the market today combine vitamin A with vitamin D and are well below the levels used in this study. Clinically, I seldom supplement vitamin A but I have used it in patients with a compromised immune system.
The bigger concern is Accutane, a synthetic derivative of vitamin A used to treat acne. The dosage is 0.5-1.0 mg/Kg/day. It comes in 10, 20 and 40 mg capsules all way above the levels used in this study. The lowest dose is 11 times the RDA for adult males and 14 times the RDA for women. However, this drug is primarily used in teenagers.
Although the drug is often effective at reducing acne, I have had several patients stop it because the side effects of bone and muscle pain were too severe. They generally report they “just feel dried out inside.”
Vitamin A supplementation is not necessary for most people if they eat red, yellow and orange vegetables daily. You may want to supplement a low-dose vitamin A to help with vitamin D absorption if the diet is suspect. More importantly, avoid synthetic vitamin A prescription drugs. The dosage is sky high and the side effects common and numerous.
Source: October 10, 2018 NIH