Thorne Zinc Picolinate 30 mg review: can zinc help testosterone?

Zinc is involved in hundreds of processes in the body, including making sperm and testosterone. Men lose some zinc through sweat, and diets low in meat, shellfish and dairy can leave them short. That's why zinc is one of the most popular supplements for men. This review looks at what the research actually shows and whether Thorne's capsule is a sensible choice.

What is in this product

According to the Amazon listing, each capsule contains 30 mg of zinc as zinc picolinate. The other ingredients are microcrystalline cellulose, a hypromellose (plant cellulose) capsule, leucine and silicon dioxide. The bottle contains 60 capsules. The listing also says the product is NSF Contents Certified, which means an outside lab has checked that the label matches what's inside.

Zinc picolinate is one of several well-absorbed forms. There's no strong evidence that it's better than zinc gluconate or citrate for raising zinc levels.

What the studies found

In a 1996 study by Prasad and colleagues, testosterone dropped in young men who were put on a low-zinc diet. In older men who were mildly low in zinc, it rose after they took zinc for six months. This is the study most often quoted about zinc and testosterone.

Things look different when zinc levels are already normal. In a 2009 trial by Koehler and colleagues, healthy men with normal zinc took a high daily dose, and their testosterone didn't change.

The pattern is the same as with vitamin D: zinc may help men who are low in it, but it is not a booster for men who already get enough.

Who it may suit

• Men who eat little meat, shellfish or dairy
• Men who train hard and sweat a lot
• Men whose doctor has found low zinc on a blood test

Who should be careful

The NIH lists 40 mg a day from food and supplements combined as the upper limit for adults. One capsule gives 30 mg, so with a normal diet you're already near that limit. Taking more than that for months can lower copper levels in the body and weaken the immune system. Zinc can also reduce how well some antibiotics and other medicines work. Talk to a doctor before taking it every day, especially for longer than a few months.

Bottom line

Thorne Zinc Picolinate is a simple, clean, tested product. It makes sense if you may be low in zinc. If you eat a varied diet with meat or seafood, a test is a better first step than a daily high-dose capsule.