Liquid L-carnitine adds about 1.2 to 1.3 kilograms of weight loss over placebo in pooled trials, so a liquid is worth it for an easy, measured daily dose, not for big results.

Red spinach extract carries about 8 times the nitrate of beet powder per gram. Beet root has more research. Compare nitrate, study doses and timing.

Yes, you can put collagen in hot coffee. Heat unfolds whole collagen, but hydrolyzed peptides are already unfolded and cut, and coffee is far too mild to break them.

Yes, modestly. Trials of hydrolyzed collagen in active adults found less joint pain during activity after 12 to 24 weeks. Here is what the research shows and what it does not.

Collagen studies used 2.5 to 15 grams a day. See the dose tested for skin, nails, joints and training, how long results took, and what it means in scoops.

Collagen is not a complete protein and will not build muscle. Whey will not do anything for your skin. Here is what each one is actually for, and whether you need both.

Whey isolate costs more and gives you less powder. Here is what the extra filtering removes, when it is worth the price, and when regular whey is the smarter buy.