The dangers of excessive vitamin supplementation

Most nutrient supplements are still safe, but there are some nutrient supplements that are harmful in excess, such as beta carotene, vitamin E, and vitamin A.

1. Excessive beta-carotene increases cancer risk

After reviewing the current evidence, the U.S. Prevention Task Force found that beta-carotene supplementation instead increased the risk of death from cardiovascular disease associated with it.

Supplementation of 20 mg or 30 mg of beta-carotene or equivalent beta-carotene + vitamin A per day significantly increased the risk of lung cancer in people who smoked or had asbestos exposure in the workplace.

20mg β-carotene is equivalent to 3333μg RAE vitamin A, which not only far exceeds the recommended intake (reference intake) for adults over 18 years old, but also exceeds the maximum tolerated dose.

Excessive consumption of beta-carotene does bring health hazards, but for people who cannot get enough vitamin A from their daily diet (fish, liver, egg yolk, mushrooms, etc.), compared with the use of vitamin A supplements, Beta-carotene supplements are still safer.

In addition, cod liver oil products and livers, such as chicken liver, foie gras, pig liver, etc., also contain a lot of vitamin A. If you like to eat animal liver, it may also lead to vitamin A poisoning.

2. Vitamin E increases the risk of hemorrhagic stroke

Vitamin E supplementation did not significantly reduce the risk or mortality of cardiovascular disease or any cancer, nor did it reduce all-cause mortality.

Conversely, when supplementing with 110IU or 200IU per day, there may be an increased risk of hemorrhagic stroke.

This point is indeed worth noting. At least a dozen years ago, I often met some nutrition scholars who would take 400IU of vitamin E a day based on experience.

For the adult population in my country, the recommended intake of vitamin E is 14 mg/d, and the maximum tolerated dose is 700 mg/d, 1 mg vitamin E = 1 IU vitamin E.

3. Vitamin A reduces bone density, risk of hepatotoxicity and teratogenicity

In addition to the aforementioned increased risk of lung cancer in high-risk individuals when combined with beta-carotene, moderate doses of vitamin A may reduce bone density and significantly increase the risk of hip fractures in women; high doses of vitamin A may Hepatotoxic or teratogenic effects.

4. High-dose vitamin B6 increases hip fracture risk

High-dose supplementation ≥ 35 mg/d was associated with an increased risk of hip fracture compared with low-dose 2 mg/d.

The recommended intake of vitamin B6 in "Chinese Residents' Dietary Nutrient Reference Intakes" is 1.4 mg/d, and the maximum tolerated dose is 60 mg/d.

5. High-dose vitamin D may increase the risk of hypercalcemia and kidney stones

In adults without underlying medical conditions, high-dose vitamin D supplementation with a daily supplemental dose of ≥ 1000 IU may increase the risk of hypercalcemia and kidney stones.

90% of the vitamin D in the human body comes from the synthesis of the skin after being exposed to ultraviolet rays, and the diet accounts for only a small part. The average person gets less than 150 IU of vitamin D from food a day.

However, many factors (regional latitude, air pollution, cloud cover, age, use of sunscreens, etc.) can affect UV exposure, especially the increase in indoor activities, which is an important factor affecting UV exposure in modern society, especially in winter.

Therefore, it is sometimes unrealistic to get enough vitamin D solely from sun exposure. It is also not recommended to increase unprotected sun exposure for vitamin D supplementation.

6. Vitamin C Linked to Increased Risk of Kidney Stones

In addition, two cohort studies in men showed that vitamin C supplementation was associated with an increased risk of kidney stones.

The recommended intake of vitamin C for adults aged 18 and over in the "Reference Intake of Dietary Nutrients for Chinese Residents" is 100 mg/d, and the maximum tolerated dose is 2000 mg/d.