Q: In my story, somebody wants to kill a man by sneaking something into his food. The rest of the family ate the same food, but nobody else became ill. What combination of foods could he have eaten or could the family have eaten to change the outcome. He has no known allergies, but the person who wanted to make him suffer winds up tried for murder.
A: There are no foods that will protect someone from the effect of other foods or toxins so that won’t work. And since you’ve ruled out a food allergy and a bacterial agent or toxic poison added to the food wouldn’t fit since it would effect everyone who consumed the food. To varying degrees, but still everyone would be effected in some way. Your best bet is to set up a situation where relatively common foods would harm an otherwise normal appearing person.
I would suggest having your character be on one of the Monoamine Oxidase Inhibitor (MAOI) drugs since these medications can have deadly reactions if certain foods are consumed. These meds are classified as psychotropic drugs (effect the psyche) and are typically used to treat depression. If your character had some degree of depression, his MD could prescribe one of these drugs and he could take it daily. The MAOIs tend to lessen depression and elevate the person’s mood. So far so good.
MAOIs alter the chemistry of the brain by blocking the enzyme monoamine oxidase, which normally breaks down norepinephrine and other neurotransmitters in the brain. Complex biochemistry and it’s not necessary to explain it. Just know that a person on a MAOI must not take certain other meds and must avoid certain foods. If not a Hypertensive Crises could ensue. In this situation the blood pressure (BP) abruptly shoots up and the person can suffer a stroke, heart attack, or sudden death.
Common MAOIs are: Nardil, Pamate, and Marplan.
Drugs that can cause a Hypertensive Reaction when taken in conjunction with one if these MAOIs include:
Diet Pills of all types
Many High Blood Pressure meds
Any Tricyclate Antidepressant such as: Elavil (amitriptyline), Sinequan (doxepin), and Tofranil (imipramine)
The list is very long but the above are a few common ones.
Foods to avoid are those that are high in the amino acid tyramine such as: certain cheeses, fava beans, smoked or pickled meats, fermented sausages (bologna, pepperoni, salami, and summer sausage), alcohol, and caffeinated drinks such as coffee, tea, colas, and chocolate. Again, the list is much longer but this gives you the idea and some choices.
If your character was taking one of the MAOIs for some mild depression, your villain could then slip him an amphetamine or a diet pill or a couple of Paxil tabs and wait.
In the food arena he could feed him one of the above foods or even more diabolical could make a caffeine broth, which he could slip into a bowl of spicy soup. This would be easy in the serving process. Finely ground coffee could be simmered for a while to leach all the caffeine out, the liquid could be boiled down to concentrate it, and then it could be strained. A couple of tablespoons of this potent liquid could easily be added to his bowl of soup—a spicy or very flavorful one to mask the bitter taste of the caffeine—and the killer could sit back and wait.
In a few minutes the reaction would occur. The victim’s blood pressure would shoot up, he would develop a severe headache, blurred vision, shortness of breath, and then collapse. He could or could not have a seizure with this. The elevated BP damages the brain and may even cause bleeding into the brain.
Or he could become short of breath and sweaty, perhaps clutch his chest and complain of chest pain, and collapse. This would look very much like a heart attack and indeed such elevated BP could precipitate a heart attack.
Of course, the ME would find caffeine in his system but if this occurred at a party where coffee and caffeinated soft drinks were available, he might assume that the victim drank some those and this in combination with his prescription medication did him in.
A similar scenario would work if he was unknowingly fed sausage or cheese. These could easily be added to some flavorful food so that he wouldn’t know he was consuming them.