Ah, vitamin C. The most popular nutrient! Somehow everybody knows that you take vitamin C when you get a cold, or feel that flu coming on. For centuries people understood that something in fresh fruits and vegetables – especially citrus fruits –prevented scurvy, a debilitating disease that often affected sailors (since they would go months without any fresh food). So what’s this vitamin all about? Let’s start with its understanding in Western physiology.
Vitamin C has a broad range of functions in the body, acting as a cofactor for numerous enzymes as well as functioning as an antioxidant. It helps protect every cell in the body from damage by free radicals, and also regenerates both vitamin E and glutathione, important antioxidants. This is especially true for white blood cells, as they generate free radicals in order to destroy invading microorganisms; vitamin C protects these cells from damage. Because of this relationship vitamin C is important for proper immune function. Vitamin C is also necessary for demethylases and thus plays an important role in gene expression.
Vitamin C is also necessary for the synthesis of numerous compounds, such as neurotransmitters, collagen, carnitine, tyrosine, various hormones, steroids, and aldosterone. It helps increase the absorption of iron from the GI tract by reducing iron ions, and thus helps prevent anemia. Vitamin C also decreases histamine levels in the blood by increasing diamine oxidase, the enzyme that breaks down histamine. This is crucial because high levels of histamine create a very allergic and reactive body, where even the smallest stimulus sets off a big allergic reaction.
Humans are among the animals that cannot manufacture vitamin C, but must obtain it from the diet. Generally this isn’t a problem, because vitamin C is present in most plant foods, as well as the various glands and organs of animals. The classic deficiency symptoms of scurvy start with fatigue and malaise, poor wound healing, easy bleeding and bruising, and progress to hair loss, loose teeth, more serious hemorrhaging, anemia, seizures, and ultimately, death.
Like all nutrients vitamin C has a place as an element of Spleen qi. In the case of this vitamin there are a number of other aspects that align it with Spleen function. The first is its role in making collagen, a key structural component of almost every part of the body. This substance literally holds the body together, and when it starts to weaken due to vitamin C deficiency the tissues just fall apart. This is the cause of easy bleeding, easy bruising, loosening of the teeth, and muscle and bone pains. Easy bleeding and bruising is a classic sign of Spleen qi deficiency, and now we see the connection to vitamin C.
The connection between the Spleen and the Lung is also highlighted by vitamin C. Though the connection is not as strong as vitamin A or D, vitamin C’s role in immune function and its role in wound healing both point towards the Lung. Due to its sour nature as an acid vitamin C likely helps to gather and contain wei-defensive qi. This also fits with its role as an antioxidant, which is a more yin function, and could be conceived of as gathering and quenching the fire of metabolism.
Vitamin C, similar to the other vitamins, also highlights the role of the Spleen in creating Blood. At the level of the Stomach it helps the body to absorb iron, particularly from non-heme sources (plants, as opposed to animals). It’s contribution to the yin element of Blood is also reflected in its effect on histamine levels. An allergic reaction can come from heat in the Blood, or from the Blood failing to contain ministerial fire. The inherent density of the Blood should buffer the sensitivity of the body to external stimuli so that the body responds appropriately, and vitamin C assists with this process. In this way vitamin C also correlates with ying-nutritive qi, and shows a bridge between ying qi and wei qi in its support of both the Blood and immune function.
Vitamin C is also connected to Kidney function. This is evident through its role in the production of steroid hormones and aldosterone, important hormones produced by the adrenal glands. This highlights the connection between the Kidney and Spleen: how Kidney yang supports Spleen yang, and how Spleen qi is the basis for Kidney qi.
Finally, similar to other vitamins, vitamin C has a jing-essence component to it. The fat soluble vitamins in particular have been studied for their effects on gene expression and cell development, and vitamin C also has DNA-level effects. Its role in demethylation reflects a jing-level activity, as it participates in DNA expression and epigenetic changes.
Vitamin C, due to its functional relationship to the Spleen, Blood, Kidney, and jing, should be grouped with the B vitamins, as they share many functions in Chinese physiology. At a chemical level it is also water soluble and thus set apart from the fat soluble vitamins. It appears in foods alongside B vitamins, and is similarly destroyed by heat.
If eating a varied diet that includes plenty of fresh fruits and vegetables vitamin C deficiency will never be an issue. For people that live traditionally in very high latitudes vitamin C is obtained from the organs of animals, such as the liver and the adrenals. Supplementing extra vitamin C doesn’t seem to help much except in people who are doing a lot of strenuous physical activity. Since physical activity would generate more free radicals increasing vitamin C consumption would help increase antioxidant activity to compensate. This would certainly be true for the B vitamins as well.
This would also apply to getting sick, as metabolism and immune activity would go up and require more of these vitamins to help keep things balanced. However, studies haven’t shown a decrease in colds for the general population. I would theorize that vitamin C (and likely B vitamins) would be useful for people that are experiencing adrenal fatigue/Kidney deficiencies, and for these people supplementing with vitamin C during a cold or flu would be helpful.