It's not worth getting sick over. But, you could also tactfully suggest since he is doing the cooking, you could help him clean up.
This reminds me of when my brother and his wife accepted a dinner invitation from a person from the hall, who lived in a half-way house.
She served them noodles with ketchup, dessert was philadelphia cream cheese on graham crackers with strawberries poured on top.
My sister-in-law just pretended to eat. My brother ate really fast, hoping to escape really fast. The woman just piled more food on his plate. This resulted in my brother being sick for weeks,so sick in fact, he lost 20lbs. The loss of the 20lbs. was the only good thing taken from the experience.
So, be careful.
