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I am a Doctor and Beg You Never Swallow This Vitamin

7 vitamins experts warn to stay away from.
FACT CHECKED BY Emilia Paluszek

According to John Hopkins Medicine, "Half of all American adults—including 70 percent of those age 65 and older—take a multivitamin or another vitamin or mineral supplement regularly," but are taking vitamins really healthy? Some experts believe vitamins are beneficial and help supplement nutrient deficiencies, but others say they're a waste of money. While that debate won't be settled anytime soon, many are in agreement that some vitamins can be harmful. Read on to find out more—and to ensure your health and the health of others, don't miss Already Had COVID? These Symptoms May "Never Go Away".


What To Know About Vitamins Before Taking Them

Female doctor talking while explaining medical treatment to patient through a video call with laptop in the consultation.

Dr. Jacob Teitelbaum, M.D., author of the best-selling From Fatigued to Fantastic shares, "Fully half of the vitamins and minerals in our food are lost in food processing. Which makes it very difficult to get optimal levels of all the vitamins and minerals without taking a daily multivitamin. Although the RDA (Recommended Daily Allowances) are adequate to prevent diseases like scurvy, they are nowhere near the optimal amounts. I do recommend multivitamins have at least 50 mg of most of the B vitamins and 150 mg of magnesium. Taking multivitamins can have powerful benefits for decreasing the risk of Alzheimer's, heart disease, and numerous other conditions. Saying that people should avoid taking multivitamins because 'they just go out in the urine' is like telling people 'don't drink any water, because it just goes out in the urine.'"

Robert Alesiani (PharmD), Chief Pharmacotherapy Officer at Tabula Rasa Healthcare says, "While available without a prescription, certain vitamins and other supplements may not only exacerbate certain medication conditions (e.g.: asthma) but may also affect (reduce or enhance) certain other chronic medication(s) absorption. Prior to starting a vitamin regimen, you should consult your physician or pharmacist to review the proposed vitamin therapy and how it may affect your current medications or chronic conditions."



Portrait of smiling young woman with Omega 3 fish oil capsule

Dr. Teitelbaum warns, "There are many forms of vitamin A, and people need a balanced amount of each. Taking over 5000 units a day of beta-carotene will make you deficient in other components of the vitamin A family, and can increase the risk of cancer,"


Vitamin E

young woman in white shirt looking at pill and holding glass of water
Shutterstock / fizkes

"This is another vitamin that has many different forms that the body requires. If you have too much of one form, it's hard for your body to find the other forms when it needs it. Think of having a drawer full of silverware. If it contains five forks and spoons but a thousand knives, it's hard to find a spoon when you need it. This is how it is with vitamin E. Too much of one type, and your body can't find the other types when it needs it. Most vitamins have the alpha-tocopherol form of vitamin E, because it is stable and low-cost. Limit the vitamin E in your multivitamin to 100 units a day, as otherwise it can cause a secondary vitamin E deficiency, and increase cancer risk. But again, I stress that by definition all vitamins are critical, and no vitamin should be avoided completely."



niacin supplements

Dr. Alesiani explains, "Over-the-counter Niacin may be used to help reduce high cholesterol and/or triglyceride levels. However, when used in conjunction with a statin, it increases the risk of myopathies or rhabdomyolysis, a condition where certain proteins, enzymes and electrolytes may be released into the blood from damaged muscles leading to muscle pain and weakness. In severe cases, this can further damage the kidneys, and heart causing permanent disability."


Potassium Supplements

Woman in white blouse holding in hand wooden spoon with suplement.

According to Dr. Alesiani, "While over-the-counter potassium supplements are far less potent than their prescription counterparts, when used in conjunction with certain prescription cardiac drugs, they may lead to unexpected and preventable side effects.  Add to this, one of the first recommendations made for people newly diagnosed with hypertension is to reduce salt intake. Most all "salt substitutes" replace sodium chloride (table salt) with potassium chloride. When these supplements are used in conjunction with ACE Inhibitors, Angiotensin Receptor Blockers (ARBs), Aldosterone Antagonists and other potassium sparing diuretics,  one's kidneys may retain more potassium allowing blood levels to increase to dangerous levels."  



Smiling young lady looking at her vitamins

"This is another form of vitamin A, and is the form found in cod liver oil," Dr. Teitelbaum says. "For women taking over 8000 units a day of retinol, it can markedly increase the risk of birth defects as well as causing loss of bone density. In women, I would keep this form of vitamin A to 5000 units daily or less as well."


Saint John's Wort

Fresh St. John's wort flowers in a bowl, top view

Dr. Alesiani states, "Saint John's Wort is often obtained over-the-counter and used as a mood elevator for patients with depression and/or post-menopausal vaso-motor symptoms ('hot flashes').. While studies do support its benefits, it may also induce a liver and gut enzyme called CYP3A4 as well as P-glycoprotein, responsible for the elimination of many prescription drugs. This can lead to reduced efficacy of these medications as they may be excreted faster than they have an opportunity to reach an effective blood level. In cases of HIV (protease inhibitors) or post-transplant anti-rejection medications, this interaction could be fatal. Also, due to its direct effect on Serotonin levels, the additive effect seen when taken with many antidepressants could lead to Serotonin Syndrome — a situation of excessive neurotransmitter, serotonin."


Vitamin K

Smiling woman taking a pill.

"Needed for healthy clotting, this vitamin is found in some supplements and green leafy vegetables like Spinach, Broccoli, Kale, etc," says Dr. Alesiani. "People taking Warfarin, an anticoagulant used to prevent blood clots, should maintain a consistent intake of all Vitamin K sources. Using Vitamin K found in supplements or changing one's intake of 'greens' may reduce or enhance the efficacy of the prescription and increase the risk of clotting or bleeding (the lesson here isn't 'not to use'… it's maintained consistency)." And to protect your life and the lives of others, don't visit any of these 35 Places You're Most Likely to Catch COVID.

Heather Newgen
Heather Newgen has two decades of experience reporting and writing about health, fitness, entertainment and travel. Heather currently freelances for several publications. Read more about Heather