Heavy Metal Toxicity and Kidney Disease

Invisible, odourless, and virtually undetectable to us, heavy metals are increasingly being recognised for their damaging effects on our health. 

Some people are surprised to find out that we are all exposed to heavy metals every day. Heavy metals are naturally present in the earth and used in many modern-day applications such as agriculture, medicine and industry. Large amounts of heavy metals get disposed of as industrial waste and they are not biodegradable, which means that they remain in the environment for long periods. For this reason, even though stricter regulations have been enforced by some countries limiting the disposal of heavy metals, high levels are still present in soil, sediment and waterways, resulting in chronic exposure in the general population.   

There are a large number of different heavy metals but they are not all bad for you. We need small amounts of some heavy metals like copper, zinc and iron to keep our bodies healthy. Heavy metals in the environment that are commonly found to be linked to adverse health problems include mercury, lead, cadmium and arsenic. 

Heavy metal toxicity

https://www.sciencedirect.com/science/article/abs/pii/S0278691514001987

Acute heavy metal poisoning happens if you get a high dose of heavy metals at one time, like in a chemical accident in a factory or after a child swallows a toy made with lead. Symptoms of acute toxicity usually come on quickly and vary depending on the toxic metal you were exposed to but may include nausea, vomiting, diarrhoea, confusion, abdominal pain, liver failure and kidney failure. Because of the severity and speed of symptoms, it’s usually easy to identify the cause.

The problem with chronic exposure to heavy metals is that symptoms can be quite nonspecific and present over time, making it difficult to identify heavy metals as the cause. Symptoms of chronic heavy metal toxicity can be similar to other health conditions and may not be immediately recognised as heavy metal toxicity. 

Through the body’s impressive detoxification systems, it is usually able to keep up with some exposure to heavy metals. The problem occurs when exposure is greater than what the body can deal with or when our ability to deal with and detoxify heavy metals is impaired. 

Heavy metal exposure

Heavy metal toxicity may occur as a result of industrial exposure, air or water pollution, foods, medicine, improperly coated food containers or lead-based paints.

Here are some of the more sources of ‘the big four’- mercury, lead, cadmium and arsenic.

Heavy metal toxicity and the kidneys

Being the major route of excretion from the body, the kidneys are highly vulnerable to heavy metal toxicity. While that is bad enough, the other problem is that when the body can’t deal with and detoxify the heavy metals we are exposed to, they start to accumulate in our organs and bones.

• Cadmium– predominantly accumulates in the kidneys and liver.
• Arsenic accumulates in the liver, kidneys, heart and lungs.
• Lead accumulates mostly in the bones but also in the brain, liver and kidneys
• Mercury accumulates in the kidneys and brain

Unfortunately, as you can see, the kidneys are a site of storage for most toxic heavy metals which is just another reason why kidney damage is a potential consequence of exposure to most heavy metals. 

Heavy metals exhibit their damaging effects on the kidneys by:

1. Facilitating oxidative stress and inflammation
2. Competing with essential metals like selenium, zinc and calcium
3. Causing mitochondrial dysfunction
4. Upregulating apoptosis- the death of kidney cells
5. Causing proteinuria (protein loss in urine)

The extent of kidney damage by heavy metals depends on the nature, the dose, route and duration of exposure. Both acute and chronic exposure has been demonstrated to cause nephropathies, with various levels of severity ranging from tubular dysfunctions like acquired Fanconi syndrome to severe renal failure leading occasionally to death. 

Cadmium Exposure and CKD

https://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S2500-50062018000100045

All heavy metals have the ability to cause kidney damage but there’s one that’s probably best known for its link to kidney damage and CKD and that is cadmium.

Cadmium is one of the main contaminants in soil and can accumulate in the body via the food chain or cigarette smoking. The kidneys are the main organ affected by cadmium exposure and toxicity. Around 50% of cadmium in the body is stored in the kidneys. 

Cadmium-induced kidney damage has been widely investigated with several studies showing that cadmium exposure may increase the risk of CKD. Cadmium nephropathy has traditionally been observed in workers exposed to high levels of cadmium, but recent data suggests that even relatively low levels of exposure increase the risk of kidney dysfunction. Cadmium-linked kidney toxicity is observed in people whose intake is well within the provisional tolerable weekly intake set by the World Health Organisation (WHO). Women, children and people with confounding health conditions such as diabetes may be especially susceptible. 

Cadmium toxicity was first described in the 19th century in those working in zinc smelters. In 1948, cadmium was first linked to renal toxicity when industrial workers exposed to cadmium dust in an electric battery plant showed evidence of proteinuria (protein loss in urine).

It’s not just the kidneys that are affected by cadmium exposure. High exposure to cadmium has also been linked to:

•     High blood pressure
•     Coronary artery disease
•     Macular degeneration
•     Diabetes
•     Cancer 
•     Osteoporosis 
•     Infertility 
•     Neurodegenerative disorders

Now we know that diabetes and high blood pressure are the two primary causes of CKD worldwide so as well as causing direct kidney damage, cadmium exposure can also increase the risk of developing CKD by causing diabetes or high blood pressure. 

Assessing Heavy Metal Exposure

There is no one perfect test to assess levels of heavy metals in the body. One of the reasons being that as I mentioned, heavy metals are stored in various organs so measuring blood levels or urine levels may not give an accurate picture of total body burden.

The most common ways to test for heavy metals is through blood tests, urine tests or hair testing. Each of these has its own pros and cons and the most appropriate test may vary depending on the heavy metal you are measuring and whether you are testing for recent or chronic exposure. 

Here are the more common tests: 

• Blood tests: these are used to detect your current heavy metal exposure. When someone is exposed to a heavy metal, it will stay in the blood for about ninety days. If a heavy metal is detected from a blood test, it usually signifies that the exposure was recent. 
• Hair testing: metals remain in the hair for a few weeks after exposure. Hair testing is a simple and effective way to assess levels of certain types of heavy metals, which blood and urine tests can’t. Although a hair test can’t detect the total body load.
• Urine testing: urine tests can be done with or without the use of a chelation agent. Some heavy metals need provocation with a chelating agent for an accurate result. Chelating agents are compounds that bind to heavy metals in your body and help remove them from your system. 

So what next?

So now we know that we are all exposed to heavy metals daily and that they can have widespread and highly damaging effects on our kidneys and virtually every other body organ. So the next obvious question is- what can we do about it?

Below are some general recommendations to help limit the build-up of heavy metals in your body and assist in the detoxification of heavy metals. If you have been tested for heavy metal exposure and have high levels of heavy metals in your system then you must work with a naturopath or functional medicine doctor who can formulate an individualised treatment plan to detox the specific heavy metals from your body. 

1. Avoid exposure- Obviously, the best thing would be to avoid exposure completely. Unfortunately, because of the ubiquitous nature of heavy metals- as in, they really are everywhere!- we can’t completely avoid being exposed to them but we can reduce/limit our exposure where possible. Have a look at the table earlier in this article for some of the more common sources of heavy metals and avoid exposure where you can.
2. Increase intake of detoxifying foods- such as cruciferous vegetables, onions, garlic, green tea, cilantro, berries, and lemon water.
3. Increase your fibre intake- fibre helps in the elimination of heavy metals by directly binding to them and then removing them from the body. Eg. psyllium husks, flaxseeds and vegetables.
4. Eat organic where possible- this will reduce your exposure to heavy metals and other chemicals that can overburden your detoxification capacity.
5. Drink filtered water
6. Maintain optimal nutrient levels- since many toxic metals mimic nutritionally essential metals, they compete for the same transport mechanisms for absorption from the intestines and uptake into cells. Therefore, adequate intake of essential trace minerals may reduce toxic metal uptake. For example, zinc or iron deficiency can increase cadmium absorption, lead absorption from the gut is blocked by calcium, iron and zinc and selenium may block the effects of lead and reduce mercury toxicity.
7. Make sure you’re getting enough antioxidants- seeing as a large amount of the damage caused by heavy metals is due to increased oxidative stress, making sure you are getting enough antioxidants through your diet can help protect against this damage. Eating a wide variety of different coloured fruits and vegetables and cooking with a variety of herbs and spices is a great way to boost your antioxidant intake.
8. Consider supplementing with antioxidants- such as N-acetyl cysteine (NAC), alpha lipoic acid, glutathione, and vitamin C to protect your organs and tissues from damage caused by heavy metal exposure.
9. Consider using Chlorella- can help with detoxification and removal of heavy metals.

Specific important nutrients:

Selenium: may inhibit mercury and lead absorption and increase toxic metal excretion. It can also reduce the toxicity of some heavy metals such as cadmium and mercury.

Vitamin C: can protect against oxidative damage caused by lead, mercury and cadmium. It may also prevent the absorption of lead as well as reduce its uptake into cells and decrease its toxicity.

Alpha lipoic acid: is a powerful antioxidant that has been shown to chelate several heavy metals including cadmium and lead. In an animal study, alpha lipoic acid reduced cadmium-associated oxidative stress and improved the activity of antioxidant enzymes in the kidneys. 

N-acetyl cysteine: helps to increase glutathione production and is effective at reducing oxidative stress due to heavy metal toxicity. In animal studies, NAC increased the excretion of lead, lowered concentrations of mercury and protected against cadmium-induced liver cell damage.

Don’t forget

Make sure you discuss any new supplements with your doctor or naturopath before starting on them to make sure they are appropriate for your use. 

On a final note

If you’re concerned about your exposure to heavy metals and particularly if you have identified ongoing exposure to any of the known sources of heavy metals then getting tested for heavy metal toxicity may be a good idea. This is particularly the case for people who don’t know the cause of their kidney disease.

And for everyone else, implementing some of the recommendations I mentioned earlier will help protect your body against the wide variety of heavy metals we are all exposed to. 

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