Vitamin C is one of the most talked-about vitamins. The nutrient gets special buzz for its immune-boosting potential but plugging vitamin C’s ability to shorten the common cold only scratches the surface of its role in the body. Wondering why we recommend vitamin C as part of our Kidney Disease Solution Program? Read on to find out.
Even before its discovery in 1932, nutrition experts recognized that something in citrus fruits could prevent scurvy, a disease that killed as many as two million sailors between 1500 and 1800. That something turned out to be vitamin C!
Vitamin C is an essential nutrient for humans and is required in the diet on a regular basis, as we are one of few species of animals that can’t synthesize it. This is because humans lack the enzyme L-gulonolactone oxidase, which is required for the conversion of glucose into vitamin C.
Actions of Vitamin C
Vitamin C is vital for our health. It helps form and maintain bones, skin, and blood vessels and is a potent antioxidant. Let’s take a look at some of vitamin C’s key actions within the body:
- Helps the body produce collagen and maintains connective tissue
- Required for the production of some neurotransmitters
- Helps the body absorb iron
- Boosts the immune system
- Enhances wound healing
- Is an important antioxidant
- Reduces inflammation
- Reduces cardiovascular risks
- Essential for the normal function of blood vessels
- Protects against diabetes and diabetic complications
Risk factors for Vitamin C deficiency
As I mentioned, our body isn’t able to make vitamin C, so we rely on our diet (or supplementation) to make sure we’re getting enough. Being a water-soluble vitamin, there is very little storage of vitamin C in the body, so we need a constant supply.
Many of us will associate vitamin C deficiency with sailors dying from scurvy during the ‘Age of Exploration.’ However, it has now become evident that vitamin C deficiency is certainly not a thing of the past.
Risk factors for vitamin C deficiency include:
- Reduced intake of fruit and vegetables
- High alcohol use
- Disorders of the GI tract like Inflammatory Bowel Disease
- Exposure to high levels of pollution
- Higher body weight & BMI
- Genetic variants
- Medical conditions including cardiovascular diseases, cancer, chronic inflammatory states, diabetes, and kidney disease
- Acute infectious diseases
- Major surgery
Symptoms of Vitamin C deficiency
Some early symptoms of vitamin C deficiency include:
- Easy bruising
- Swollen and/or bleeding gums
- Poor wound healing
- Poor appetite and weight loss
- Emotional changes such as irritability and depression
- Vague muscle and joint pains
Why do we recommend vitamin C for people with CKD?
There’s no one answer to this question. Vitamin C performs a variety of actions that make it a key nutrient for people with CKD.
Firstly, we know that plasma vitamin C levels are lower in people with CKD which is due to a variety of reasons such as reduced dietary intake for those following low potassium diets, increases levels of oxidative stress and inflammation, proteinuria which causes an increase in urinary loss of vitamin C and use of medications known to deplete vitamin C such as aspirin and diuretics.
Let’s dig a little deeper into what some of the key actions of vitamin C are that make it such an important nutrient for those with CKD.
Antioxidant and Anti-inflammatory
Now, if you’ve read any of my other articles, you’re probably familiar with the negative effects that oxidative stress and inflammation have on the kidneys but let’s recap anyway.
Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) or ‘free radicals in cells and tissues and antioxidants that neutralize these free radicals. When we have too much oxidative stress in the body or not enough antioxidants, we get damage to the body’s cells, proteins, and DNA. Oxidative stress can also cause or worsen chronic inflammation. Oxidative stress and inflammation are involved in the development and progression of many chronic diseases and the kidneys are especially vulnerable to inflammation, oxidative stress, and damage from free radicals.
High levels of oxidative stress have been found in the early stages of CKD and they increase in parallel with the progression of CKD and this is further exacerbated in dialysis patients.
The progression of CKD is closely associated with systemic inflammation and oxidative stress, which are responsible for the manifestation of several complications associated with CKD including malnutrition, atherosclerosis, coronary artery calcification, heart failure, anemia and mineral, and bone disorders, as well as enhanced cardiovascular mortality. For this reason, the treatment of inflammation and oxidative stress is of primary importance in CKD.
But what does this have to do with vitamin C?
Well, vitamin C is one of the most important water-soluble antioxidants. It acts as an antioxidant and free-radical scavenger that protects cells and organs from oxidative damage and its antioxidant and anti-inflammatory actions are responsible for many of the health benefits vitamin C provides.
Vitamin C is oxidized instead of lipid membranes, proteins, carbohydrates, and DNA to protect these structures from being damaged.
Vitamin C also participates in the recycling of other important antioxidants, for example, vitamin C is known to regenerate vitamin E, basically giving it a second chance at life so it can continue to quench free radicals and exert its beneficial effects on the body.
Vitamin C has been shown to reduce oxidative damage, inflammation, and kidney injury in several animal models and in kidney injury caused by nephrotoxins and lack of oxygen.
One of vitamin C’s other superpowers is its beneficial effects on endothelial function.
The endothelium is a thin membrane that lines the inside of the heart and blood vessels. Endothelial cells release substances that control contraction and relaxation of blood vessels, enzymes that control blood clotting, immune function and platelet adhesion (the attachment of platelets to blood vessel walls or other cells).
Endothelial function refers to the ability of the endothelium to adequately perform its physiological role such as the regulation of blood pressure and preventing and stopping bleeding. When there are disturbances in the endothelium it plays a central role in the pathogenesis of a number of diseases including high blood pressure, peripheral vascular disease, stroke, heart disease, diabetes, insulin resistance, and chronic kidney disease.
Don’t forget that the kidneys are made up of blood vessels- arteries, veins, and capillaries- so when there is dysfunction in the endothelium the kidneys are one of the organs that are affected. In people with CKD, endothelial damage is thought to be a central process towards progressive kidney damage.
Vitamin C has consistently been shown that improves endothelial function. In fact, a meta-analysis from 44 clinical trials found there was a significant positive effect of vitamin C on endothelial function with stronger effects in those at higher cardiovascular disease risk (such as people with CKD).
Vitamin C increases nitric oxide bioavailability in endothelial cells which is a major player in preserving the integrity of blood vessels and elicits vasodilation or relaxation of blood vessels helping to lower blood pressure and improve blood flow throughout the body, including to the kidneys.
Vitamin C supplementation was shown to reduce the risk of cardiovascular disease by 25% and has been associated with significant regression of atherosclerosis (build-up of plaque in arteries). Atherosclerosis increases the risk of heart attacks and strokes and blocks blood flow and oxygen delivery throughout the body including to the kidneys. Lack of blood and oxygen to the kidneys is another cause of kidney damage.
Blood Pressure Regulation
High blood pressure is the second leading cause of CKD and people with CKD are at a greater risk of developing high blood pressure which doesn’t just contribute to the risk of developing the cardiovascular disease but also contributes to further kidney damage.
A meta-analysis of 29 studies found that vitamin C supplementation significantly reduced systolic blood pressure and diastolic blood pressure. It lowers blood pressure largely through improving nitric oxide activity and improving endothelial function
Diabetes is the leading cause of CKD and like people with CKD, people with diabetes have been shown to have lower plasma vitamin C levels. Studies have also shown that lower vitamin C levels are associated with an increased risk of developing diabetes.
Studies have shown that type two diabetics supplementing with vitamin C had a significant decrease in fasting blood sugar, triglycerides, LDL cholesterol, HbA1c, and serum insulin.
Improving glycaemic control is super important when it comes to preventing diabetic damage like kidney disease (diabetic nephropathy). High glucose levels cause increased levels of oxidative stress which is a large part of what causes complications like kidney disease or nerve damage (diabetic neuropathy). This means that vitamin C isn’t just beneficial from a blood sugar lowering perspective but also to reduce the oxidative damage that elevated glucose levels can cause.
Vitamin C and Kidney Stones
Now to the question we frequently get asked by people following our Kidney Disease Solution Program- ‘Why do you recommend vitamin C when it causes kidney stones?’
Well, here’s the thing- there is very little evidence that supplementing with vitamin C causes kidney stones. Vitamin C may increase urinary oxalate concentrations which have prompted the belief that vitamin C will then cause kidney stones even though most studies do not back this up.
I’m not going to go into this any further here because this is something we’ve addressed in another article so if you’re interested in having a better understanding of how vitamin C doesn’t cause kidney stones you can find that article here.
So let’s review why we recommend vitamin C as part of our Kidney Disease Solution Program:
- It reduces inflammation and oxidative stress
- It lowers blood pressure
- It improves blood flow throughout the body and to the kidneys
- It Improves endothelial function
- It reduces cardiovascular disease risk factors
- It reduces the formation of plaque in arteries
- It reduces blood clot formation
Before starting any new supplements, make sure you discuss this with your healthcare provider to ensure they are appropriate for your use.
Hopefully, you’ve learned a few things about vitamin C that you didn’t already know and have a better understanding of why it’s of benefit for people with CKD. If you’ve found this article useful please let me know by clicking the ‘SHARE’ button below and head over to our Facebook page to leave any questions or comments.