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 health 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 are not the only ones because the benefits often do not outweigh the risks,” says JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Boston, Massachusetts.

This is not to say that certain groups of people do not need to supplement certain nutrients at certain points in their lives; it’s just that most people don’t need to supplement all the vitamins they think they do.

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

Such recommendations are particularly relevant to fat-soluble vitamins.

Soluble in water vs

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

Water-soluble vitamins, which include vitamin C and the eight B vitamins, are dissolved, processed and metabolized quickly in the body, and are not stored for later use.

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

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

That’s why Tolerable Upper Intake Level (UL) safety guidelines are provided by the National Academies of Sciences, Engineering and Medicine to show the maximum amount of certain vitamins that can be safely consumed without adverse health effects.

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

Among the four fat-soluble vitamins, experts say that 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 from natural food sources, such as beef liver, sweet potatoes, spinach, carrots or pumpkin pie in recommended doses – 900 micrograms per day for adult men and 700 micrograms per day for adult women – the vitamin A is considered safe and essential.

The maximum intake limit of vitamin A is set at 3,000 micrograms, although it is important to note that such allowances include the consumption or absorption of everyone sources of vitamin A including food, supplements and creams/lotions containing retinol. (For context, consider that a single 3-ounce serving of fried beef liver contains 6,582 micrograms of the vitamin).

Exceeding the UL is dangerous and “a single large dose can contribute to toxicity,” explains Yufang Lin, a primary care physician at 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 cause harm to the mother and the developing fetus, causing an increased risk of birth defects of the eyes, heart, organs and nervous system central,” says Messer. .

Even in modest amounts and outside of pregnancy, “vitamin A supplements have been linked to skin irritation and an increased risk of bone fractures,” says Manson.

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

There are also problems with the inclusion of vitamin A 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 it’s for this reason that some multivitamin brands only include vitamin A as an ingredient in the form of beta-carotene. (Studies show that beta-carotene is converted into vitamin A in the body, but carries fewer risks associated with other forms).

In addition, although some studies show that vitamin A derived from a balanced diet could reduce the risk of certain cancers; the NIH Office of Dietary Supplements notes that its supplement form could grow up the risk of certain cancers due to the role of vitamin A in the regulation of cell growth and differentiation.

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

Concerns about vitamin E

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

When found naturally in foods such as wheat germ oil, avocados, fish, seeds and nuts such as 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 Department of Nutrition at the Harvard TH Chan School of Public Health notes that the safety profile of its synthetic form is a matter of debate among academics: “Due to occasional reports of negative health effects of supplements of vitamin E, scientists 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 many forms – some of which are more studied than others.

“Vitamin E has eight chemical forms naturally, while most vitamin E supplements are synthetic alpha-tocopherols,” explains Lin. It is this form of alpha-tocopherol that seems to carry more risks than other forms of vitamin E. “This is an argument that it is better to eat foods that are rich in vitamin E instead of taking a synthetic supplement.”

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

There is also some confusion with how much vitamin E can be consumed safely. The recommended dietary allowance (RDA) of vitamin E is 15 milligrams for adult men and adult women, but their daily intake limit is 1,000 milligrams. The NIH Office of Dietary Supplements notes that “taking vitamin E supplements even below these upper limits may cause harm.”

Indeed, clinical research shows that taking just 268 milligrams of vitamin E every day can increase the risk of prostate cancer in men 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 the downsides,” adds Manson. “Randomized trials of vitamin E have documented problems even in moderate amounts.”

Higher doses of vitamin E supplementation can also interfere with blood clotting, which can cause hemorrhages, says Jessika Rose, bariatric dietitian for the University of Maryland Upper Chesapeake Health.

Because of these problems and others, research published by the American Heart Association shows that supplemental vitamin E is no longer recommended at the highest levels needed to help protect against chronic diseases such as cancer, l Arthritis and cataracts.

“Ultimately, it’s about assessing the balance between potential risks and rewards,” explains Messer.

Lack of regulation for dietary supplements

Another area of ​​concern for experts regarding water- and fat-soluble vitamins is that additional nutrients are not regulated by the US Food and Drug Administration (FDA) using the same criteria as foods and drugs.

This can lead to unfounded 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 amount of ingredients claimed, while 40 percent of the supplements did not contain any of the claimed ingredients,” says Messer. “Furthermore, 12 percent of supplements contain undeclared ingredients, which is prohibited by the FDA.”

It is up to consumers, therefore, to choose reputable supplement brands and buy products that have been tested and labeled by established third parties. “Be very careful of any supplement that claims it can treat a disease because supplements are not allowed to make such claims,” ​​says Lin.

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

“It’s a common misconception that vitamin supplements are beneficial for everyone,” says Messer. “They may be beneficial for some individuals in particular situations, but they are not universally necessary, they can be expensive, and they are not entirely without risks.”