Is exceeding the US RDA for vitamin C dangerous?

Question

When I travel I take vitamin C supplements. The product I use has 1000 mg of vitamin C. When traveling I take multiple doses every day. This way exceeds the US RDA of 90 mg for adult males. Is it bad to take too much vitamin C?

Answer 1

Vitamin C (ascorbic acid - an antioxidant and reducing agent) is water soluble (so dietary excesses not absorbed), and excesses in the blood rapidly excreted in the urine. It exhibits remarkably low toxicity , however LD₅₀ in humans remains unknown given lack of any accidental or intentional poisoning death data.

Government recommended intake:

• United States vitamin C dose recommendations:

  • Recommended Dietary Allowance (adult male): 90 mg per day
  • Recommended Dietary Allowance (adult female): 75 mg per day
  • Tolerable Upper Intake Level (adult male): 2,000 mg per day
  • Tolerable Upper Intake Level (adult female): 2,000 mg per day
• 40 milligrams per day or 280 milligrams per week taken all at once: the United Kingdom's Food Standards Agency,
• 45 milligrams per day 300 milligrams per week: the World Health Organization,
• 80 milligrams per day: the European Commission's Council on nutrition labeling,
• 90 mg/day (males) and 75 mg/day (females): Health Canada 2007,
• 60–95 milligrams per day: United States' National Academy of Sciences,
• 100 milligrams per day: Japan's National Institute of Health and Nutrition, however the NIHN did not set a Tolerable Upper Intake Level.

Based on US upper level recommendations taking up to 1g per day is still fine, however it depends on your body tolerance and previous intake (as for some 5-10g could be still normal), especially if your body needs it for optimum health and to meet stresses or infections. Although the body's maximal store of vitamin C is largely determined by the renal threshold for blood.

However if you exceed the upper limits of your body/bowel tolerance, in general any drug overdose is dangerous causing some side effects. Relatively large doses of ascorbic acid may cause indigestion, particularly when taken on an empty stomach and it can case diarrhoea. In one trial in 1936 (6g doses) toxic manifestations were observed in 5/29 adults and 4/93. Symptoms of Vitamin C overdose could include: skin rashes, nausea, vomiting, diarrhoea, facial flushing, headache, fatigue and disturbed sleep. As well as itchy skin (prurutis), dizziness and abdominal pain.

It's usually advised to take smaller doses more frequently (e.g. ever hour), than larger doses in short amount of time in order to simulate endogenous production and increase your tolerance threshold. On the other hand your body would "learn" daily intake and it will expect similar doses on daily basis.

Source: Vitamin C

Answer 2

Overloading on vitamin C won't cause death. At around 1000 mg, you will probably have nausea, diarrhea, and stomach aches. 2000 mg is the daily limit, and if you get that high, you will experience more severe side-affects such as severe headaches, vomiting, heartburn, insomnia, and even kidney stones. You probably shouldn't have that much vitamin C, so if you have to take multiple 1000 mg doses everyday, you should talk to your doctor.

In conclusion, taking that much vitamin C is not necessarily "dangerous", but it can lead to major discomfort and could possible put you in the hospital.

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^{Vitamin Overdose: Taking Too Many Vitamins Can Be Bad For Your Health, But How Many Would It Take To Kill You?}

Answer 3

There are two important types of vitamins.

Fat soluble and Water Soluble.

Your body will store fat soluble vitamins but will discard excess water soluble vitamins in your urine. Because of this fat soluble vitamins carry a greater risk of toxicity while water soluble carry a greater risk of deficiency.

Some examples of fat soluble ¹ A, D, E, K

and water soluble ² B, C

You're fine with taking 1k of C everyday but it's unlikely to benefit you anymore once the body absorbs the 90mg it needs. Splitting a pill up into quarters (250mg) and consuming it with food (to increase chance of absorption) could work too.

As for the dangerous part, yes. Despite what it may seem, more does not equal better. Balance and moderation is key. Anything is dangerous if overdosed, including water, oxygen, or ____

Answer 4

While taking 1 gram or even more may not be acutely toxic as pointed out in the other answers, you should consider the question of why humans or other animals have not evolved to rid themselves of free radicals to the same degree as when one takes 1 gram or more of vitamin C. So, one can question if the naive picture of free radicals is actually correct, some recent research results suggest it may not be, see e.g. here:

It is important to consider that free radicals are not always damaging to cells; in many cases, they serve as signals to adapt muscle cells to exercise via modulation of gene expression (9, 33). We have found that training causes an increase in 2 major antioxidant enzymes (Mn-SOD and GPx) in skeletal muscle. We were surprised to see that vitamin C prevents these beneficial effects of training. On the basis of the paradigm that enzymatic antioxidant systems such as Mn-SOD and GPx provide a first-line defense against ROS, it is expected that exercise may induce these protective mechanisms. Moderate exercise increases life span and decreases disability in rats (12) and humans (15). We report here that exercise training causes an increase in the expression of antioxidant enzymes, which is prevented by the administration of vitamin C.

So, it is likely harmful and you should not use it. You can also take this perspective. We don't know all the relevant facts about free radicals, the way the human body gets rid of them, all the self repair mechanisms that the body does in addition to removing the free radicals, any use of free radicals in the immune system etc. etc. The simplistic idea to just flood the body with vitamin C is not based on a deep understanding of how the body actually works. The relevant mechanisms have evolved over more than 600 million years.

Now, we know that vitamin C is produced by animals themselves who don't get it in their diet. Only when the diet contains sufficient amounts of vitamin C will the production of vitamin C have stopped. But this implies that more vitamin C is not better, because otherwise our bodies would just produce vitamin C itself in addition to what we get from food. In fact, the more we get from food the harder the body will work to remove it, but that takes a bit of time and with 1 gram per day you are going to get an equilibrium situation where there is just too much vitamin C in the body.

Any theoretical argument why 1 gram per day is good should be based on a deep knowledge of the relevant facts which has never been presented. To the contrary, there are only good arguments why it is harmful (in the sense of not optimal for health). But of course, one can always do clinical trials, but those that have been conducted point to harmful effects consistent with the theoretical arguments.

Answer 5

According to Dr. Cathcart's data (10 years, 9,000 patients) a normal person can tolerate 4 to 15 grams of vitamin C divided into 4 to 6 doses over a period of 24 hours without having diarrhea.