Recommended Daily Dose of Vitamin C 

 

When taken within regular recommended doses, supplements of this medicine are safe and do not cause any toxicity. Its lack of toxicity is because it is water-soluble and does not build up in the body's fat. As such, when you consume too much of it, your body urinates excess amounts. It is only when truly excessive doses, called megadoses, are taken that problems occur. These problems include gut upset, excess iron, and kidney stones.

 

A mega dose of it is the equivalent of consistently taking 30 oranges a day or up to 20 bell peppers each day. It is almost impossible to "overdose on Vit-C" through diet alone. It is difficult but not impossible to reach an overdose with supplements. 

 

The recommended daily level of this nutrient, which is also called ascorbic acid, is between 65 to 90 milligrams (mg) a day for adults.

 

 

Vitamin C Megadose

 

In clinically supervised settings, doses of up to 2000mg are used.

 

Side effects, such as upset stomach and diarrhoea, start to occur above this dose.

 

Kidney stones have occurred in individuals taking 4000mg daily for several months. Those predisposed to kidney stones are more at risk of this side effect of excessive intake of this nutrient -  even at lower doses than 4000mg daily.

 

Clinical trials using mega doses of ascorbic acid for COVID 19 and other infections have used doses of up to 9000mg, but great care is required. 

 

 

Factors that Affect Absorption of Vitamin C

 

Age, race, and gender affect how effectively you absorb Vit-C. For example, the ageing process results in a noticeable down-regulation of one or more subtypes of ascorbic acid transporter. This reduction in this nutrient leads to a reduced immune function, which may increase the risk of cancer and a weaker immune response to infections. In practical terms, this means that a similar level of Vitamin C will significantly benefit the immunity of a younger person rather than an older person. 

 

In general, sticking to a level of 90mg a day, even when combined with a varied healthy diet will not cause problems. If you experience health issues when taking any multivitamin please contact one of our pharmacists or your local pharmacist.

 

Do not exceed the recommended daily dose of any medicine.

 

 

 

 

Upset Stomach

 

Digestive issues such as diarrhoea or nausea are common with higher doses of ascorbic acid. It is suggested that large doses can cause acid reflux, but there is little actual evidence to prove this.

 

Iron overload

 

One of the key benefits of Vit C is that it increases your absorption of Iron. This interaction is beneficial in people who find Iron medicines leave them constipated or with an upset stomach.

 

Ironically, this interaction with Iron is also one of the downsides of taking high doses of this nutrient. Increased levels of ascorbic acid lead to higher levels of Iron in the blood.

 

High levels of Iron is called hemochromatosis. A genetic condition in men often causes hemochromatosis. When you have too much iron in your blood, the body stores it in organs such as the pancreas, heart, and liver. This excess storage of Iron can cause damage to these organs.

 

Signs of excessive Iron include:

  • Abdominal and joint pain.
  • Weakness, fatigue, impotence, and low libido.
  • Heart failure.
  • Liver failure.
  • Diabetes.
  • Greyish/bronze skin colour.

 

It increases the absorption of iron because it can bind to a type of Iron the body finds hard to absorb. This non-heme Iron comes from plants, and usually, the body is relatively inefficient at absorbing it from the diet. When ascorbic acid bonds with non-heme Iron, this type of iron crosses from the gut to the blood and from there to the liver in more significant quantities. Again, this is a great benefit of Vit-C for vegetarians and vegans, but it can cause problems in excess.

 

 

 

Kidney stones

 

One of the beautiful things about this nutrient is that the body only takes in what it needs. When you consume an excess of it, the body excretes it as urine. Before being excreted in the urine, Vit-C goes through a chemical reaction in the body called oxidation. The resultant metabolites or by-product of excessive intake are called an oxalate.

 

In excess, these oxalates can crystallize and form kidney stones. The higher the concentration of oxalates in your urine, the greater the risk of developing kidney stones.  In rare cases, this can lead to kidney failure.

 

 

Bone spurs

 

While there is some evidence that ascorbic acid can help prevent and slow the development of rheumatoid arthritis, there are several papers that highlight that taking excessive or mega does may lead to painful bone spurs. A bone spur is a bony projection found on the edge of bones. They occur at joints and can occur on the spine, foot, hips, etc. They are associated with osteoarthritis and linked to extra-large doses of Vit C. These bone spurs are often unnoticeable and go undiagnosed. Sometimes they develop and cause pain and immobility. Their treatment depends on where the bone spur occurs on the body. More research is still required, given the confusing relationship between this nutrient and a reduced occurrence of rheumatoid arthritis and its positive link with bone spurs. Nonetheless staying within recommended daily doses is essential.

 

 

 

Vitamin C Interactions

 

Food

 

The most obvious way your level of this nutrient may be altered is when you dramatically increase your intake from what you eat. For an adult male, the recommended daily dose is 90mg a day; it is 75mg for a woman. A little more is required when breastfeeding (120mg) and less for children (15mg to 45mg). Certain foods are rich in it:

 

A half a cup of the following fruit and vegetables yield the following amount of Vit-C:

  • Raw red peppers – 70mg
  • Raw green peppers – 60mg
  • Strawberries – 50mg
  • Cooked broccoli - 50mg
  • Cooked Brussel sprouts – 50mg

 

150ml of grapefruit juice gives 70mg, while Orange juice gives over 90mg. 150ml of tomato juice only contains 30mg. 

 

Painkillers

 

NSAIDs include medicines such as Ibuprofen (Nurofen), Naproxen, Ponston and diclofenac. NSAIDs and aspirin both lower blood levels of Vit C . Aspirin blocks the absorption of ascorbic acid while NSAIDs work to increase its excretion in urine. Both interactions lower the body's Vit C levels.

 

There is a second interaction with NSAIDs & this supplement. Vit-C increases the levels of these drugs in the body and extreme doses of either of these medicines can lead to toxicity. Ascorbic acid also increases the level of paracetamol in the blood by blocking its excretion.

Generally, this interaction is mild and only occurs with high doses of either medicine.

 

Antacids

 

This nutrient may increase blood levels of Aluminium-containing antacids such as Gaviscon and Maalox. This interaction is mild at rarely occurs at the recommended daily dose. Losec (omeprazole) a proton pump inhibitor lowers the bioavailability of Vit C.

 

OCP and HRT

 

Oestrogen the oral contraceptive pill and Hormone replacement therapy medicines can increase the excretion of ascorbic acid. Conversely, these medicines' blood levels can rise when you take this nutrient.

 

Warfarin

 

Below 1000mg a day of Vit C there appears to be minimal interaction between these medicines

 

Other Prescription medicines

 

This nutrient may interact with:

  • Barbiturates, 
  • Chemotherapy drugs (as it is an antioxidant it can make these drug regimes more effective), 
  • Nitrates used for angina (itmay reduce their effectiveness), 
  • HIV medicines (it lowers levels of indinavir (Crixivan)) 
  • Antibiotics (it may increase levels of tetracycline, minocycline, and doxycycline).

 

Always speak with your pharmacist before taking any medicine. Generally, if you feel your Vitamin C levels are low or your diet lacks this essential nutrient, a supplement is perfectly safe.

 

 

 

 

 

Ann O’Flynn B.Pharm, MA, BSc, MPSI

 

Ann is the owner of dPharmacy and has a particular interest in Health foods and supplements. Ann is a Tutor pharmacist and has gained numerous qualifications in alternative therapies - which she uses alongside her extensive clinical training. If you have any queries on medicines or health foods please reach out to us by email, text or phone.

 

 

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