Bad Stuff in Food: Risk Analysis and Political Commentary: Personal Dietary Risk Assessment

Public vs Individual Health

A public decision is about public welfare. Decisions made by the Federal government, where I used to work, are invariably about the welfare of the U.S. population in general. It’s not about you. Yes, you have a voice, but so do a lot of other people who may want something different than what you want. If you have a loud voice or you have enough money to buy a politician or three, your opinion will be considered more. That is as true in the Public Health Service as it is in the rest of the Federal government. It’s called politics.

But, there is another reason why public health risk assessments tend to focus on populations; it’s easier. Information about potential health risks usually come, at least in part, from epidemiology studies that compare what happens in different populations with different variables that may be causally linked to a particular disease. Discerning a causal relationship for any individual in a study is usually impossible. Therefore, risk assessments based on epidemiological data almost always provide risk estimates that either involve the frequency of a disease in a population, or the average magnitude of an effect in a population. But, you are not an average person, and neither is anyone else. Everyone knows that, but an estimate for a fictional average person is far easier to produce that an estimate for each and every individual. It’s not about you.

Consumption Advice for Chemical Contaminants in Food

For a chemist, food is made up of chemicals. Some are natural, some are not. Virtually any chemical constituent, including water, can be poisonous if consumed in large enough quantities. Yet consumption advice for toxicological reasons is rare. The main reason for this is that any chemical that is added to food (I.e. is not natural) must be approved first. If there is a risk worthy of consumption advice, it won’t be approved. Naturally occurring chemicals are another story. They are not as tightly regulated because they can’t be. Often the choice is whether or not the food that the chemical is in can be sold or not. For example, a handful of raw bitter almonds that contain high levels of cyanogenic glycosides can be lethal, and as a result cannot be sold in the United States. But, there are also unintentional chemical contaminants that are present in food that wouldn’t be considered safe if they were added. Yet, they also aren’t poisonous enough to warrant banning the food. So, consumption advice may be the only viable option.

But, if someone like the U.S. Environmental Protection Agency, the U.S. Food and Drug Administration, or Consumer Reports advises you to modify your diet, you would like to know why, right? At least I would if I didn’t already. I don’t necessarily want to be “safe” or “protected”, especially if I’m really the one who has to do the protecting. If there is a risk of eating too much of something, I want to know what the risk is. Is it big like smoking or driving on the beltway, or small like getting hit by a meteor? If it’s the latter, I’m probably going to eat it anyway. I take my chances with meteors. Hell, back when I had to get to work, I even drove on the beltway several times a week. I’m cutting back on that now.

Providing individual risk information to consumers is rare, but it can be done. The impact of smoking on life expectancy is a familiar example. Jha et al (2013) who estimated that a lifetime of smoking reduced life expectancy by about 10 years, which is useful information when considering the possibility of starting the habit of smoking. Furthermore, the risk will be reduced if you stop. Shaw et al (2000) provided an alternative way of presenting information about reduced life expectancy by estimating a reduced life expectancy of 11 minutes per cigarette.

An Individual Dietary Risk Assessment Paradigm

So, if you really want to know what your risk is, you are going to have to figure it yourself. Since I’m retired and don’t have anything better to do, I’ll help. Here’s the process:

Hazard Identification. As far as I’m concerned, the grocery store aisles are a sea of risks. Take your pick. Actually, as far as me helping goes, I only plan on putting up some risk assessment software (probably Excel worksheets, but maybe I can do something web-based) for methylmercury in fish and arsenic in rice because they are the subject of current consumption advice. Maybe I’ll add more if there is some demand for it.
Exposure Assessment. This is where substantial personalization is possible. You know what you eat and what your body weight is, I don’t. I can help with the amount of the chemical in the food. That will allow us to estimate the amount of the chemical you consume, otherwise known as your “dose”.
Dose-Response Modeling. A dose-response model is a mathematical equation that describes the causal relationship between exposure and a bad outcome that would be nice to avoid. Usually, these are models based on population studies that may not be quite right for you. Therefore, since we don’t know if you are more or less susceptible than an “average” person, most of the population variability that anyone knows about, will end up being an uncertainty for you. Also, since the risks are small and unmeasurable, educated guesses are the best thing going. Unless you want to volunteer for a toxicology experiment, that’s the best anyone can do. So, expect lots of uncertainty. There, you have been warned.
Risk Estimation. Plug the dose from the exposure assessment into the dose-response model and then you will have it -- a highly uncertain risk with a specific magnitude. Welcome to my world.
Risk Management. In general, the issue is this: The health effects that might occur from even the worst chemical contaminants in food, like methylmercury in fish and arsenic in rice are “marginal”, which means somewhat more than negligible, but far short of alarming. They may be worth considering, but don’t lose any sleep over it. In fact, the stress might be the bigger risk -- but that’s not my area. In any case, you decide. Because this time, it is about you.

References

Jha P, Ramasundarahettige, C, Landsman, V, Rostron B, Thun M, Anderson RN., McAfee T and Peto R (2013). 21st-Century Hazards of Smoking and Benefits of Cessation in the United States. N Engl J Med 368:341-350.

Shaw M, Mitchell R, and Dorling D (2000). Time for a smoke? One cigarette reduces your life by 11 minutes. BMJ 320: 53.