The geriatric population in 1st world countries (i.e. England, Germany, USA, Canada) are more at risk of toxicity (too much vitamin A) rather than a deficiency of vitamin A. Toxicity risk increases in the older population for a few reasons: a slower clearance of vitamin A from the kidneys, a higher rate of vitamin A absorption than in younger adults, and widespread use of vitamin A supplementation and fortified foods (i.e. Ensure).
Hypervitaminosis A (a fancy word to use when someone has taken too much vitamin A) occurs due to the over-consumption of preformed vitamin A but, importantly, not dietary carotenoids (naturally occurring vitamin A from fruits and vegetables). Let me explain the different forms of vitamin A!
Sources of Vitamin A
Vitamin A are fat-soluble compounds. Preformed vitamin A (also known as retinol) is found naturally in animal products, dairy, liver, and fish. If you ever looked on a nutrition facts label of cow's milk, you may have noticed that when the fat is taken out of whole milk to make skim, 1%, or 2%, vitamin A is then added back in supplement form. That is because whole milk already has vitamin A and it is removed when the fat is removed.
Other sources of vitamin A in our foods are in the form of carotenoids. These are all plant-based sources of vitamin A. Fruits and vegetables (orange and green colors), sweet potato, and spinach are examples. Dietary sources of vitamin A are considered safe in terms of minimal risk of overdosing. Supplemental vitamin A is when risk increases. Getting the dosage right matters.
Pharmacological doses in the treatment of acute promyelocytic leukemia, retinitis pigmentosa, and various skin diseases is associated with vitamin A toxicity (Linus Pauling Institute, 2019).
Preformed vitamin A is rapidly absorbed and slowly cleared. Toxicity can be caused rapidly with a high dose of vitamin A (preformed) or slowly with chronic low dose. And the elderly may be more susceptible of sub-clinical toxicity than younger adults with the same dosage. Vitamin A toxicity is enhanced by chronic alcohol consumption which narrows the therapeutic window of supplemental vitamin A in alcoholics (Linus Pauling Institute, 2019).
Vitamin A supplements available on the market are in the forms of retinyl palmitate, retinyl acetate, and B-carotene. Linus Pauling Institute (2019) recommends not exceeding the RDA (recommended dietary allowance as detailed below) and warns that Daily Values on nutrition labels are based on the RDA established in 1968 rather than the most recent RDA.
So how much vitamin A per day is recommended?
Recommended Daily Allowance is as follows:
Males: 900 ug RAE/d
Females: 700 ug RAE/d
Tolerable Upper Limit (the highest amount of vitamin A a person can tolerate before it is toxic): 3000 ug RAE/d or 10,000 IU/d (does not apply to dietary carotenoids from fruits or vegetables)
Signs/Symptoms of Vitamin A Toxicity
Acute vitamin A toxicity (more rare) from high dosing of performed vitamin A supplementation: nausea, headache, fatigue, loss of appetite, dizziness, dry skin, desquamation, cerebral edema
Chronic vitamin A toxicity (more common) from long-term supplementation of preformed vitamin A: dry itchy skin, desquamation, anorexia, weight loss, headache, cerebral edema, enlarged liver, enlarged spleen, anemia, bone/joint pain
Severe vitamin A toxicity: liver fibrosis, hemorrhage, coma; thinning of eyebrows; sparse, coarse hair; cheilosis; and bulging eyes
Signs of toxicity are associated with long-term consumption of vitamin A in excess of 10 times the RDA. More research is needed to examine sub-clinical vitamin A toxicity.
Increased cancer risk with excessive B-carotene supplementation. Most notable, increased osteoporotic fracture risk with excessive retinol supplementation. Even “high normal” as well as “high” plasma levels of vitamin A can lead to an increased risk of fracture (Russell, 2000).
Medical Nutrition Therapy
Linus Pauling Institute (2019) recommends not exceeding RDA, and that supplementation in older adults should not exceed 2500 IU (650 ug) of preformed vitamin A (usually labeled vitamin A acetate or vitamin A palmitate) and no more than 2500 IU of additional vitamin A as B-carotene. Avoid high dose supplementation without medical supervision.
Vitamin A should be obtained through dietary sources. Dietary carotenoid sources are safe.
Milk is an easy way to for older adults to obtain vitamin A (Russell, 2000).
References
Linus Pauling Institute. (2019). Micronutrients for older adults. Retrieved from
https://lpi.oregonstate.edu/mic/life-stages/older-adults
Russell, R. (2000). The vitamin A spectrum: from deficiency to toxicity. American Journal of Clinical Nutrition, 71, 878–884.