I find it hard to get enough omega-3 and vitamin-d as well as potassium just from food alone as recommended dosages is 2-3g; 1000iu and 4700 ?

Food then supplement: Evidence currently suggests that eating healthy is best way to stay healthy. Attempts to isolate specific factors from food and sell said factors as supplements have not demonstrated much benefit. With that said, if you don't like or can't eat enough fish, dairy & fruits/veggies, i suppose you could/should take supplements. But i'd still recommend real food first. Btw, fda doesn't approve suppleme.

SupplementsNOTneeded: A new study shows that fish oil (omega3source) does not prevent heart events as we thought earlier. Vitamin d is not needed as long as you are exposed to sunlight and remember milk is fortified with vitamin d. Also, the average diet has plenty of potassium. Potassium supplement can be harmful if you have unrecognized kidney disease.Your doc can check potassium, chemistry and vit d blood levels.

Supplements: You are right. Omega 3 supplementation is safe and beneficial. Purity matters. Vit D supplementation is safe and helpful. Take 1000 iu. Potassium you can getfrom food. Citrus, melons, tomato, potato, peaches, apricots, mango,