Science, Art, Litt, Science based Art & Science Communication
Q: I am confused about a few tips on nutrition. Some say some foods are good. While others say they are bad. Who should we believe?
Recently I read a research paper. It tells us a lot about why this thing happens.
Despite our understanding of nutrition expanding remarkably in recent times, few aspects of our diet continue to confuse and divide the experts like nitrate.
For a long time nitrate has been viewed warily, with previous research showing it could potentially be linked to causing cancer.
However, subsequent research has revealed dietary nitrate also has various cardiovascular health benefits, which could help reduce the risk of related conditions such as heart disease, dementia and diabetes.
Hmmm! Now who do you believe? Take nitrates or not? How can one dietary compound have such contrasting potential risks and benefits?
So some other scientists tried to find the answers and made a review of nitrate research and they say the key may lie in where nitrate comes from.
We get nitrate from three major dietary sources: meat, water and vegetables.
Nitrate's reputation as a health threat stems from 1970, when two studies showed it can form N-nitrosamines, which are highly carcinogenic in laboratory animals.
Nitrosamines (or more formally N-Nitrosamines) are chemical compounds that can form in food as a result of food preparation and processing. They have been found in several types of foodstuffs such as cured meat products, processed fish, cocoa, beer and other alcoholic beverages (1).
Nitrosamines are formed by reaction of secondary or tertiary amines with a nitrosating agent. In foods, the nitrosating agent is usually nitrous anhydride, formed from nitrite in acidic, aqueous solution. Food constituents and the physical make-up of the food can affect nitrosamine formation (1).
Ascorbic acid and sulfur dioxide are used to inhibit nitrosamine formation in foods. Nitrosodimethylamine has been shown to be formed in certain foods as a result of the direct-fire drying process. In this case, oxides of nitrogen in the drying air nitrosate amines in the food being dried. The volatile nitrosamine which occurs most commonly in food is nitrosodimethylamine, and nitrosopyrrolidine occurs to a lesser extent (1).
So nitrate is not good if it comes from nonvegetarian sources. Cooking and processing of food makes it take a dangerous form.
However, no human studies have confirmed its potential dangers, and clinical and observational studies support nitrate preventing cardiovascular disease, if it's sourced from vegetables.
Despite recent research indicating the source of nitrate may affect its health benefits and risks, current dietary guidelines relating to nitrate have been in place since the 1970s and don't differentiate between nitrate from meat, vegetables and water.
Unlike meat and water-derived nitrate, nitrate-rich vegetables contain high levels of vitamin C and/or polyphenols that may inhibit formation of those harmful N-nitrosamines associated with cancer.
The public are unlikely to listen to messages to increase intake of nitrate-rich vegetables, if they are concerned about a link between nitrate intake and cancer. And if this difference between non-veg and veg nitrates is not explained properly, people will get confused and refuse to eat all nitrate containing food.
So current evidence suggests people should aim to get their nitrate from vegetables—but there is no need to go overboard. Dark green, leafy vegetables and beetroot are good sources, and research shows one cup of raw, or half a cup cooked per day is enough to have the benefits on cardiovascular health (2).
Now do you understand why this confusion occurs? Those researchers who are dealing with meat say nitrate can cause cancer. Those who deal with processed foods and cooked meat say it is harmful.
While those researchers who deal with vegetarian food say it is beneficial.
Journalists report these things without clearly mentioning what is what as they themselves cannot understand this or don't have full knowledge.
Only experts/researchers who do meta analyses can differentiate between these different types and clear the matter.
So listen to only experts.
2. Catherine P. Bondonno et al, Nitrate: The Dr. Jekyll and Mr. Hyde of human health?, Trends in Food Science & Technology (2023). DOI: 10.1016/j.tifs.2023.03.014