Phenylalanine comes in several forms as a supplement:
L-phenylalanine is an essential amino acid. It's also found in protein in the foods we eat.
DL-phenylalanine, which contains both the D- and L-forms
Over the years, people have taken tribulus in an attempt to enhance athletic performance and for a wide range of health issues that may include heart and circulatory conditions and sexual issues.
But does it work? Limited studies show it might be helpful in lessening symptoms of angina and in enhancing athletic performance. There have also been some studies that show some benefit to people with certain sexual problems and to those suffering from infertility.
Evidence is lacking that shows benefits of tribulus for other health conditions.
With a lack of research to draw on, it's not clear what a safe dosage is. Also, quality and active ingredients in supplements may vary widely from maker to maker. This makes it difficult to set a standard dose. However, one standardized extract is used at a dose of 85-250 milligrams daily.
Can you get tribulus naturally from foods?
No. In fact it is unsafe to eat the spine-covered fruit. There have been reports showing that eating it may cause collapsed lungs.