Arsenic and heart disease risk: A global research project
Heart disease doesn't recognise boundaries and nor does research. Dr Rajiv Chowdhury is working on global health projects, including looking at the effects of arsenic on heart disease risk. He tells Sarah Brealey how his international approach helps patients.
Taking a global view of research means we can benefit from the best minds around the world. That’s what Dr Rajiv Chowdhury does at the University of Cambridge. This means collaborating on BHF-funded projects with researchers from South America to South Asia.
“Almost 80 per cent of the global population live outside of western countries,” says Dr Chowdhury. “In these lower and middle income countries we have the majority of global cases of heart and circulatory disease. But the research that has been done in those countries has been minimal.”
The populations of different countries often have a different risk profile and genetic makeup. For example, researchers have discovered new genes linked to heart failure in people in South Asia. This is crucial for developing new drugs. Dr Chowdhury explains: “While important genes are often discovered in specific populations, they offer crucial insights into the mechanisms of disease as a whole, and therefore can progress medicine by developing new drugs that can target those pathways. And if we discover new genes, which can help us develop new drugs, that is very important to western medications and western populations too.”
Arsenic and heart disease risk
Dr Chowdhury is the lead investigator on several collaborative global health projects, which are addressing local challenges and global questions. With colleagues from Cambridge’s Department of Public Health (headed by BHF Professor John Danesh), he works in Bangladesh to study the health effects of arsenic in drinking water and foods.
Arsenic is most often associated with an increased risk of cancer, but Dr Chowdhury is studying how it may also increase your risk of heart disease.
“In the 70s and 80s in Bangladesh there was a heavy burden of waterborne disease, so they dug deep wells underground,” Dr Chowdhury says. “That helped in reducing infectious diseases but also brought arsenic, which is present naturally in the Ganges Delta, into the water supply.”
This isn’t just an issue for people in South Asia – it has relevance for people in the UK and many other parts of the world. Research by the University of Aberdeen in 2008 found that baby rice products on sale in the UK had arsenic levels higher than those that would be allowed in drinking water. The levels depend on where the rice is grown – rice from north India and Nepal has lower levels, while rice from Bangladesh and the US has higher levels.
Toenail arsenic is the gold standard for measuring arsenic
In January 2016, maximum arsenic levels in rice products came into force in Europe, although there is no compulsory testing when rice enters the UK. The UK Food Standards Agency advises that children under five shouldn’t be given rice milk as an alternative to cows’ milk or breast milk, to reduce their exposure.
Around 65 countries worldwide have been affected by toxic mineral contamination, from the US to the UK (unsafe levels of arsenic have been found in drinking water boreholes in Cornwall). It’s in everyone’s interest that we learn more about this problem.
We know arsenic is dangerous, but there’s more to find out. Does arsenic raise the risk of heart and circulatory disease even at the low levels of exposure seen in many western countries? And what happens when arsenic occurs alongside other toxic metals, such as mercury, lead and cadmium?
“We are studying the effects of these metals in combination,” says Dr Chowdhury. “We are also studying arsenic exposure in combination with air pollution, to see how it affects the risk of heart disease, pregnancy outcomes and child development.”
Dr Chowdhury and colleagues (Professor Danesh and Dr Emanuele Di Angelantonio) are gathering information from tens of thousands of volunteers, including dietary surveys, blood samples and toenail clippings.
“Toenail arsenic is the gold standard for measuring arsenic,” says Dr Chowdhury. “It is very stable and reflective of several years of exposure to arsenic. It is a reliable measure and is unaffected by other disease, such as whether you’ve had a heart attack. It works well to compare people who have had a heart attack or not.”
The effects of intermarriage and lifestyle factors
Dr Chowdhury’s group is also looking at the effect of marriages between people who are related. “If your parents are related, you are more likely to inherit a faulty gene. Preliminary reports from his group indicate that intermarriage can significantly increase cardiovascular risk.
“In countries such as Malaysia, Pakistan and Bangladesh, up to 50 per cent of marriages are consanguineous [between blood relatives]. It’s common in many south Asian countries and some north African countries, and in many cases among migrant populations in Europe too.
We are very keen for British scientists to play more of a leading role in global collaborative research
The researchers are also investigating the role of lifestyle factors. “These include the use of certain cooking fats, for example ghee, and chewable tobacco consumption – common in both native and immigrant ethnic populations,” says Dr Chowdhury. “It’s important that we are able to give people information about these potentially preventable risk factors.”
Meanwhile, back in Cambridge, Dr Chowdhury says: “We are very keen for British scientists to play more of a leading role in global collaborative research, and so is the BHF. Grants this Cambridge department has received from the BHF have helped us, as a group, to set up large and hopefully landmark global cardiovascular health studies, looking at new and unexplored areas. The BHF has been crucial to our work.”