Can you guess what all of these foods have in common?
They are all excellent sources of vitamin C.
Here's something fascinating that I recently learned about vitamin C. The number one storage site for vitamin C in the body is ... the adrenal glands. Your body needs vitamin C to make norepinephrine, an essential hormone and neurotransmitter that's important for your 'fight or flight' response. If you're constantly stressed, this depletes the levels of vitamin C in your adrenal cortex and could compromise your adrenal function.
Unlike most mammals and other animals, humans do not have the ability to synthesise vitamin C and must obtain it from the diet. If you use it and you don't keep eating it, you lose it. And if you lose it, that's a problem. Your body relies on vitamin C to complete many vital functions because vitamin C acts as a cofactor for a number of enzymes that make important things happen in the body. For example, if you don't have vitamin C, your body can't:
Make collagen. You need collagen to maintain connective tissue, heal injuries to tissue, and remodel bone.
Make carnitine. Important for using fatty acids for energy.
Protect immune cells called neutrophils. If you're exposed to bacteria or a virus, neutrophils defend your body and release chemicals to neutralise the threat. In this process, neutrophils soak up vitamin C so that the neutrophil itself doesn't self-destruct in the firing line.
How much vitamin C do you need each day?
This one's a little complicated. Most of the time, the RDA (USA) and RDI (AU) match. But for vitamin C, they don't.
The RDA in the US is 75 mg for an adult female and 90 mg for an adult male.
The RDI is Australia is set at just 45 mg for both females and males.
However, if you dig a little deeper you'll see that in Australia there's also a 'Suggested Dietary Target' set for vitamin C at 190 mg for women and 220 mg for men.* You won't find this in an app like Cronometer though, so remember to factor it into your calculations. We also know that an upper intake level of 2 g/day (that's g, not mg) is sufficient to prevent susceptible adults from experiencing related digestive troubles.
Based on this, I aim for > 200 mg daily. I'd rather be on the optimal end of the scale than on the average side.**
What are some excellent food sources of vitamin C?
Most people think vitamin C = oranges. I'm a big fan of oranges, but there's other fantastic foods that you can add to your day to bump up your vitamin C.
Here's a list of some of my favourite foods in order of vitamin C content based on NCCDB data. I've used realistic portion sizes so that you can easily put this into practice and be able to tally your daily intake.
Red capsicum. The surprise winner. 1 cup of red capsicum contains 117 mg of vitamin C.
Pineapple. 1 cup of pineapple contains 79 mg.
Oranges. 1 medium orange contains about 70 mg.
Kiwi fruit. Just 1 kiwi fruit contains 64 mg.
Parsley. Half a cup of fresh parsley contains 40 mg. (Tip: It's easy to consume that if you chop it finely and toss it in a salad.)
Tomato. 1 large tomato contains 25 mg.
Lemon. The juice from one lemon contains 18 mg.
All up, this plate contains about 320 mg of vitamin C. That's 3.5 x the RDI.
A tip for preparing your foods to maximise vitamin C content
If you can, eat these foods fresh and either raw or lightly cooked. Vitamin C is sensitive to light, air and heat. If you're cooking a food that contains vitamin C you'll still access some of it (for example, broccoli or brussel sprouts), just keep in mind that it loses about 25 % of its vitamin C content due to cooking.
* An SDT is set for nutrients if there is a reasonable body of evidence of a potential preventive effect in relation to chronic disease at levels substantially higher than the RDI.
** There's also evidence that 200 mg is the upper limits for maximal bioavailability. After that, bioavailability starts to decrease an the body excretes a lot more vitamin C.
Linus Pauling Institute, Micronutrient Information Center, Vitamin C.
The Medical Biochemistry, Introduction to Vitamins and Minerals.
Dr Rhonda Patrick. Listen to her episode on the Joe Rogan podcast.
Nutrient References Values for Australia and New Zealand, Suggested Dietary Targets to Reduce Chronic Disease Risk.
Cronometer to access NCCDB data.