Two of my favorite foods have been in the news in the past several months, dark chocolate and flaxseeds because sadly, high levels of the toxic metal have been found in many brands. Cadmium transfers to plants from soil at a higher rate than other toxic metals and thus it's ubiquitous in our food supply and there is no safe level of cadmium in food. If you are someone with bones (kidneys or lungs) you should care. I see many women with osteoporosis and in many cases cadmium is an issue. In this article I will share some more information about cadmium, its impact on bone health, and discuss the Consumer Reports on cadmium levels in chocolate and the recent Consumer Labs report cadmium in flaxseed and share which brands have the lowest and highest levels.

For too long, the way we have learned about the ill effects on human health of such toxicants has been through the fall out of pollution. Such is the case with cadmium. In 1968, Toyama Prefecture, Japan, recognized the harmful effects of cadmium on bone when metal mining contaminated the water supply with cadmium, which then spread to the rice grown in the water. Those who ate the rice developed itai-itai (it hurts, it hurts) disease, which caused kidney stones, kidney failure, hypercalciuria, bone pain, and osteoporosis. Measuring body load of cadmium is difficult, as the level in urine only indicates current exposure and weakly correlates with body load. Cadmium has a long biological half-life and accumulates in kidneys and bones. Even a low urinary cadmium level of 0.5 μg/g creatinine increases the risk of osteoporosis, fracture, kidney disease, and various cancers. Safe levels of cadmium in humans have not been established.  

A study in Sweden showed that women with higher cadmium levels, even non-smokers, had a higher risk of osteoporosis. Another study showed that women with urinary cadmium levels between 0.50 and 1.00 μg/g creatinine had a 43% higher risk for hip-BMD-defined osteoporosis compared to those with lower levels. Increasing evidence suggests that in the US female population aged 50 years or older, the primary cause of cadmium-related osteoporosis risk is dietary cadmium rather than tobacco. Another challenge for women is that low iron stores, common in those with heavy periods and multiple pregnancies, can lead to higher cadmium retention, and thus toxicity. While comparable research on bone health has not yet been conducted on men, I have no doubt that men's bones are susceptible as well.  

How Does Cadmium Cause Bone Damage?  

Environmental Toxins are a Major Cause of Bone Loss by Pizzorno and Pizzorno explains how cadmium negatively affects bone metabolism through several mechanisms, with the most significant being the impairment of essential kidney functions and direct damage to osteoblasts. Vitamin D requires two hydroxylations, one in the liver and the other in the kidneys, to produce its most active form, vitamin D3, also known as calcitriol. 1) Cadmium disrupts this process by poisoning the kidney enzyme responsible for the conversion of inactive vitamin D (25-OH-D) to active vitamin D3 (1,25-OH-D3) which then acts on the small intestine, bone, and kidney to regulate calcium and phosphate metabolism. Active vitamin D3 enhances calcium and phosphate absorption from the intestines, promotes bone mineralization, so important for bone health. 2) Cadmium also impairs the kidney's ability to excrete toxins and reabsorb essential molecules and minerals, leading to increased calcium loss in urine. So, if you have high urine calcium, cadmium toxicity could be a potential cause. Moreover, cadmium inhibits the activity of alkaline phosphatase, produced by osteoblasts, which deposits calcium into newly formed bone. 3) Cadmium also decreases bone collagen content by stimulating osteoclast formation and activity, which breaks down the collagen matrix as part of normal remodeling. 4) Finally, cadmium activates toxic response pathways in bone cells, further stimulating osteoclast bone resorption.

Cadmium in Food

The amount of cadmium intake in an average person can be estimated through the Total Diet Study (TDS) and food frequency questionnaires (FFQ). TDS is a food safety monitoring program that collects samples of foodstuffs from supermarkets and retail stores to analyze food additives, pesticide residues, contaminants, and nutrients. This program provides an effective way to determine the contribution of each food item to the total intake of cadmium, with staples that are frequently consumed in large quantities found to have the highest levels of cadmium. TDS data is available for limited countries such as the United States, Australia, Sweden, France, Chile, Spain, Serbia, and Denmark, and indicates that the average consumer's cadmium intake ranges from 8 to 25 μg/day, with staples like rice, potatoes, and wheat contributing 40-60% of the total dietary cadmium intake. Other sources of cadmium include shellfish (ie clams, oysters, mussels, scallops), crustaceans (ie shrimp, lobster, crab), mollusks (ie squid, octopus, snails), offal (organ meats), and spinach. This information was reviewed in a study by Satarug et al. 

The amount of cadmium present in food is not the only factor that determines dietary exposure to the metal; consumption patterns are also important. Some foods, such as organ meats, have high cadmium levels but are not frequently consumed by the general population and therefore do not significantly contribute to overall intake. On the other hand, foods with low cadmium levels but high consumption rates in certain populations can be major sources of cadmium. For example, I and many of my patients consume A LOT of dark chocolate and flaxseed, which is why the recent December 2022 Consumer Reports study findings on cadmium (and lead) in popular brands of dark chocolate bars and the Consumer Labs report on cadmium in flaxseeds stood out to me and prompted me to share this information with you all. 

The Consumer Reports study on lead and cadmium in dark chocolate found several brands to be safer including: Mast Organic Dark Chocolate 80% Cocao, Taza Organic Deliciously Dark Chocolate 80% Cacao; Ghirardelli Intense Dark Chocolate 86% Cacao and Intense Dark Chocolate Twilight Delight 72% Cacao, and Valrhona Abinao Dark Chocolate 85% Cacao. These brands had lower levels of both lead and cadmium compared to other brands tested in the study. In the Consumerlab.com report on flaxseeds, the 365 [Whole Foods Market] Whole Flaxseed was found to be the safest choice for adults and children. Several other brands had either toxic levels of cadmium or levels known to be unsafe for children. However, it's important to note that even these "safer" brands still contain measurable levels of these heavy metals. 

Strategies to Decrease the Body Burden of Cadmium 

We cannot hide from it as cadmium is naturally occurring at low levels in the earth's crust, and as a result, all foods may contain small amounts of cadmium, particularly if the soil is deficient in zinc. However, crops grown with high-phosphate fertilizers typically contain higher levels of cadmium, as these fertilizers can have cadmium amounts of up to 300 mg/kg. Exposure to cadmium can be increased by living close to a smelter or mining operation. 

Per Environmental Toxins are a Major Cause of Bone Loss by Pizzorno and Pizzorno, there are three ways to decrease the body burden of cadmium.

1) The primary strategy for reducing exposure to cadmium is to avoid it. This includes stopping direct and indirect exposure to cigarette smoke, avoiding the consumption of oysters, scallops, and shellfish from coastal waters contaminated with cadmium, and avoiding all foods grown with high-phosphate fertilizers (ie non-organic soy beans). Additionally, air particulates are an under considered source of cadmium (and other toxins) by the average person. Not allowing outdoor shoes to be worn inside the house, dusting regularly, and using air filters such as MERV-12 (preferred) or above in whole house forced-air systems or HEPA filters in frequently used rooms are other ways to minimize exposure. Further, children's jewelry imported from China should be avoided since a 2010 analysis by the US Consumer Product Safety Commission found that 12% of 103 analyzed items contained at least 10% cadmium, with one item containing a staggering 91% cadmium.

2) The second strategy is to ensure adequate consumption of foods rich in trace minerals that compete with cadmium, such as copper, iron, zinc, and selenium.

3) The third strategy is to increase excretion, but this must be done with great care to avoid increasing tissue release of cadmium faster than excretion, which can cause redistribution and further toxic effects. At this point, based on the research of Dr. Stephen Genuis and his team, saunas seem to be the safest and most effective method, though they are slow.

The majority of chronic diseases can now be attributed to toxicant exposure. This quote by my colleague Joseph Pizzorno, ND really strikes home for me as more and more we are seeing how we cannot hide from these environmental toxins:

"Somewhat independent of people’s choices, the things which in the past have been normally considered healthy, or at least neutral, are now becoming significant sources of toxins for people." ~Joseph Pizzorno, ND

All of us are exposed to cadmium and due to dietary, health and genetic differences, some of us have a larger body burden than others. Exploring the body burden of environmental toxicants is an important aspect of prevention. The good news is that naturopathic doctors, like myself, are trained in this and naturopathic medicine has a lot to offer those who are dealing with a high burden of cadmium and other toxicants. If this is an area that you have yet to explore, it's important and I'd love to help. Environmental medicine is a passion of mine, when we can remove even just one burden from a person's toxic load, it is amazing how the body can shift back into balance and so many other areas of health then improve!

Dr. Sarah Giardenelli is a naturopathic doctor, acupuncturist, and owner of Collective Health Center in downtown Leesburg, Virginia, with a passion for helping people explore root causes of their health concerns, including environmental toxicants which are now a driver of most chronic disease. When we identify and address root causes healing can begin.