Vitamins A and E: Why they can do more harm than good

There are many important supplements that benefit people with specific deficiencies or certain medical conditions; but research shows, and experts say, that some synthetic vitamins may do more harm than good.

“Everyone is always looking for that magic pill that will give them great health, but dietary supplements just aren’t it because the benefits often don’t outweigh the risks,” says JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Boston, Massachusetts.

This does not mean that some groups of people do not need to supplement certain nutrients at certain times in their lives; it’s just that most people don’t need to supplement with all the vitamins they think they do.

“In general, I don’t recommend the use of vitamin supplements unless there is a specific reason to do so,” says Walter Willett, a professor of epidemiology and nutrition at the Harvard TH Chan School of Public Health.

Such advice applies especially to fat-soluble vitamins.

Water soluble versus fat soluble

Water- and fat-soluble nutrients are absorbed differently in the body.

Water-soluble vitamins, which include vitamin C and all eight B vitamins, dissolve, process and metabolize quickly in the body and are not stored for later use.

“Excess water-soluble vitamins are excreted in the urine,” explains Alice Lichtenstein, director of the cardiovascular nutrition team at the USDA Jean Mayer Center for Human Nutrition Research on Aging at Tufts University.

On the other hand, the fat-soluble nutrients vitamins A, D, E, and Kare are stored in the liver and adipose (adipose) tissue throughout the body for future use. While this helps build up vitamin D stores during the summer sun to compensate for less sunlight exposure during the winter months, it also means that these vitamins can accumulate to potentially toxic levels.

For this reason, the National Academies of Sciences, Engineering, and Medicine provide Upper Tolerable Intake Level (UL) safety guidelines to indicate the maximum amount of certain vitamins that can be safely consumed without adverse health effects.

“Fat-soluble vitamins have a lower UL compared to water-soluble vitamins, emphasizing the need for caution when consuming them,” explains Jen Messer, registered dietitian and president-elect of the New Hampshire Academy of Nutrition and Dietetics.

Among the four fat-soluble vitamins, experts say vitamins A and E require more caution than others.

Vitamin A concerns

Vitamin A is important for vision, growth, reproduction and immune health. When consumed through natural food sources such as beef liver, sweet potatoes, spinach, carrots or pumpkin pie in the recommended doses of 900 micrograms per day for adult men and 700 micrograms per day for adult women, vitamin A is considered safe and essential.

The maximum upper limit of daily intake of vitamin A is set at 3,000 micrograms, although it is important to note that such amounts include consumption or absorption all sources of vitamin A, including foods, supplements, and creams/lotions that contain retinol. (For context, consider that one 3-ounce serving of fried beef liver contains 6,582 micrograms of the vitamin.)

Exceeding the UL is dangerous, and “one large dose can contribute to toxicity,” explains Yufang Lin, a primary care physician at the Cleveland Clinic’s Center for Integrative Medicine. Such toxicity can cause problems such as joint pain, liver damage and birth defects.

“Vitamin A is essential for normal fetal development, but too much can harm both the mother and the developing fetus, causing an increased risk of birth defects in the eyes, heart, organs and central nervous system,” says Messer. .

Even in modest amounts outside of pregnancy, “vitamin A supplements are associated with skin irritation and an increased risk of bone fractures,” says Manson.

Research published earlier this year suggests that vitamin A toxicity may also result from topical vitamin A (retinol) used to treat acne and psoriasis.

There were even problems with including vitamin As in multivitamins. “At one point there was concern about the amount of vitamin A in multivitamin supplements and bone loss in older women,” explains Lichtenstein. She says that for this reason, some multivitamin brands now only include vitamin A as an ingredient in the form of beta-carotene. (Studies show that beta-carotene is converted to vitamin A in the body, but carries fewer risks associated with other forms.)

Furthermore, although some studies show that vitamin A obtained from a balanced diet can reduce the risk of certain cancers; The NIH Office of Dietary Supplements notes that its supplement form could size up the risk of certain cancers due to the role of vitamin As in regulating cell growth and differentiation.

“Long-term high-dose vitamin A intake can also lead to liver disease, elevated blood lipids, bone and muscle pain, and vision problems,” says Kate Zeratsky, a registered dietitian at the Mayo Clinic in Rochester, MN. “Early signs of vitamin A toxicity can include dry skin, nausea, headache, fatigue, enlarged liver and hair loss, among other possible symptoms.”

Vitamin E concerns

Vitamin E is an even more controversial fat-soluble supplement.

When it occurs naturally in foods like wheat germ oil, avocados, fish, seeds and nuts like almonds, hazelnuts and peanuts, vitamin E is a powerful antioxidant that protects cells from the effects of free radicals and improves skin and eye health.

But the Harvard TH Chan School of Public Health’s Department of Nutrition notes that the safety profile of its synthetic form is a matter of debate among academics: Because of occasional reports of adverse health effects of vitamin E supplements, scientists have debated whether these supplements could be harmful. and even increase the risk of death.”

One of the points of controversy and confusion regarding vitamin E is the fact that the nutrient has multiple forms, some of which have been studied more than others.

“Vitamin E occurs naturally in eight chemical forms, while most vitamin E supplements are synthetic alpha-tocopherol,” Lin explains. This form of alpha-tocopherol appears to carry more risk than other forms of vitamin E. “This is an argument that it is better to eat foods rich in vitamin E than to take a synthetic supplement.”

Zeratsky agrees. “I believe there is a need to better understand how the different forms of vitamin E work and function in our bodies,” she says.

There is also some confusion about how much vitamin E you can safely consume. The Recommended Daily Allowance (RDA) of vitamin E is 15 milligrams for both adult men and adult women, but its upper daily intake limit is 1,000 milligrams. The NIH Office of Dietary Supplements notes that taking vitamin E supplements even below these upper limits can cause harm.

Indeed, clinical research shows that taking just 268 milligrams of vitamin E per day can increase a man’s risk of prostate cancer by 17 percent. The form used in supplements has also been linked to lung cancer.

“And you don’t have to reach toxic levels to experience downsides,” Manson adds. “Randomized trials of vitamin E have documented problems even in moderate amounts.”

Higher doses of vitamin E supplements can also interfere with blood clotting, which can cause bleeding, says Jessica Rose, a bariatric dietitian at the University of Maryland Upper Chesapeake Health.

Because of these and other problems, research published by the American Heart Association indicates that supplemental vitamin E is no longer recommended at the higher levels needed to protect against chronic diseases such as cancer, arthritis, and cataracts.

“At the end of the day, it’s about assessing the balance between potential risks and rewards,” explains Messer.

Lack of regulations for dietary supplements

Another area of ​​concern for experts affecting water- and fat-soluble vitamins is that the US Food and Drug Administration (FDA) does not regulate supplemental nutrients using the same criteria as foods and drugs.

This can lead to false claims and even labels that misrepresent the ingredients in each supplement bottle. “According to a recent independent analysis of 57 dietary supplements, 84 percent of them did not contain the required amount of ingredients, while 40 percent of the supplements did not contain any of the listed ingredients,” says Messer. “Furthermore, 12 percent of the supplements contained undeclared ingredients, which are prohibited by the FDA.”

So, it is up to consumers to choose reputable supplement brands and to purchase products that have been tested and labeled by established third parties. “And be very careful with any supplement that claims it can treat a disease because supplements are not allowed to make such claims,” ​​Lynn says.

It is also important to check the daily dose recommendations and upper limits of dietary supplements and to make sure that one supplement you are taking will not interfere with another. “Talk to your doctor or a dietitian to help you determine the specific nutrients you need,” Rose suggests.

“It’s a common misconception that vitamin supplements are good for everyone,” says Messer. “They may be useful for certain individuals in certain situations, but they are not universally necessary, they can be expensive and they are not completely without risk.”