Some vitamins are good for your health but others are not, even can be dangerous.
Aim to get 55 micrograms of selenium from natural sources like Brazil nuts, tuna, and beef. Some people take selenium to prevent cancer, especially prostate cancer. But those good intentions could actually be working against you — one major study found that taking selenium could actually increase risk of high-grade prostate cancer in men who were already high in the mineral. (One real prostate-cancer prevention? Ejaculating. Find out how many times to ejaculate every month to cut cancer risk.) Selenium could also be one of the worst supplements for diabetes. Another 2007 study found a 50% increased risk of Type 2 diabetes in people who took 200 micrograms a day. Bottom line: Don't take it.
Toxicity in vitamin A is known as hypervitaminosis A. Symptoms of vitamin A toxicity are mild headaches, nausea, hair loss and blurred vision. Major adverse effects of vitamin A toxicity include birth defects, liver abnormalities, reduced bone mineral density, and central nervous system disorders, according to the NIH. The UL for adults is 3,000 micrograms of vitamin A daily. The recommended daily intake, however, is just 700 micrograms for women and 900 micrograms for men.
3.Excessive Vitamin E
There are at least 8 related types of vitamin E. This family of fat-soluble compounds have similar antioxidant activity, particularly alpha-tocopherol but also including other isomers of tocopherol and the compound tocotrienol. We can obtain vitamin E through our diet as it is found in fish, vegetable oil, nuts, sunflower, wheat, and green leafy vegetables. Vitamin E acts as an antioxidant and free-radical scavenger in lipophilic environments. Bile is required for absorption. Vitamin E is fat-soluble and is stored in adipose tissue (fat tissue), as well as in the liver, and muscle. Vitamin E may block the absorption of vitamins A and K. Moreover, vitamin E decreases low-density lipoprotein (LDL) cholesterol levels at doses more than 400 IU/day.
Vitamin E was once heralded as a way to prevent cardiovascular disease, cancer, and Alzheimer’s disease. Paradoxically, subsequent research has shown that excessive vitamin E may harm one’s health, increasing the risk of cancer and death. The Cochrane systematic review found that the overall risk of death was higher in men and women who supplemented with a high dose of vitamin E than in those who didn’t. The participants in these studies were taking 400 IU of vitamin E – or more daily. Supranormal doses that are practically impossible to obtain from food alone.
Perhaps the most popular single vitamin supplement, vitamin C occurs in plentiful amounts in many fresh fruits and vegetables. In the early days of global exploration, sailors often died from scurvy, caused by the lack of vitamin C. Way back in the 1700's, Scottish doctor James Lind famously conducted an experiment that proved that citrus fruit cured scurvy, although vitamin C itself wasn't discovered until the 1930s.
Vitamin C gained its current popularity through the woefully misguided efforts of Linus Pauling, who published a book in 1970 recommending mega-doses of C to prevent the common cold. Although Pauling was a brilliant chemist (and Nobel laureate), he was completely wrong about vitamin C, as Paul Offit explains in detail in his new book, "Do You Believe in Magic?"
Aim to get 400 micrograms of folic acid, found in fortified bread and breakfast cereal, legumes, and asparagus, every day. Because it's been shown to reduce the risk of neural-tube defects in newborns, some women take it while pregnant. But some doctors warn supplementation of food with folic acid could be fueling rising rates of colon cancer. Bottom line: Only women who are pregnant or may become pregnant are advised to take it. If you're a mom-to-be, you'll relate to these thoughts every woman has with a positive pregnancy test.
Excess vitamin D accumulates in the liver and can cause bone calcification, headaches, weakness, nausea, vomiting, constipation, kidney stones and frequent thirst and urination. Severe symptoms range from kidney damage and bone weakness to growth retardation in infants and children. The UL for vitamin D is 100 micrograms per day, and you need just 20 micrograms daily to maintain your health.
7.Excessive Vitamin B-6
B vitamins are essential for optimal health, helping our bodies convert our food into fuel and promoting overall good memory and healthy skin. Most people who eat a healthy diet get enough B vitamins from food.
Vitamin B-6, also called pyridoxine, is found in fish, pork, poultry, grains, and legumes. Vitamin B-6 supplements usually contain between 5 and 500 mg per tablet. Vitamin B-6 aids in protein and amino acid metabolism. Bodybuilders use the supplement, as do people with the following conditions, including, carpal tunnel syndrome, schizophrenia, premenstrual syndrome (PMS), childhood autism and attention deficit hyperactivity disorder (ADHD).
Research shows that taking more than 100 milligrams of vitamin B-6 over an extended period – considered to be a large dose – can cause a form of nerve damage called neuropathy, which causes an abnormal sensation in the nerves.
This is the big one. With nearly 40% of Americans taking a multi-vitamin, they must be good for you, right? But a huge study that I wrote about last year, looking at 38,772 women over 25 years, found that the overall risk of death increased with long-term use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc, and copper. Death, one must admit, is a pretty bad outcome.
On the evidence, supplementing your diet with any of these 5 vitamins carries little or no benefit, and may cause you harm. This is why we do science, people. Our intuitions aren't always right: just because a little bit of something is good for you does not mean that a lot of it is even better.
Vitamins don't "boost your immune system," they don't promote joint health, they don't reduce stress, and they don't help prevent colds or other common ailments.
Foods rich in vitamin B12 include fish and shellfish, lean beef, and fortified breakfast cereal; it's a vitamin that vegetarians and vegans tend to be low in. Aim to get 2.4 micrograms from those sources every day. Vitamin B12 deficiency, which can cause anemia and dementia, is a problem for some seniors, so supplements can help. But high doses of B12 have not been proved to prevent cognitive loss, and they don't boost energy. Bottom line: Take it only if your doctor recommends it. Ask your doctor whether you've been showing signs of nutrient deficiency.
The daily recommended allowance for zinc — found in oysters, lean beef, and breakfast cereal — is 11 milligrams for males and 8 milligrams for females. There are claims that the mineral can prevent and treat symptoms of the common cold, but the evidence doesn't hold up. A few studies suggest that cold symptoms are less severe and resolve sooner in zinc users, but others show no benefit. Plus, high doses can actually weaken the immune system, so you may want to stick with these ways to treat a cold instead. Bottom line: Don't take it except for occasional use of zinc lozenges or sprays for colds.