Humacyte Chairman and CEO Carrie Cox is a 35-year veteran in the pharmaceutical industry and a longtime board member for three S&P 500 companies. Over the past five years, these companies have well-outperformed their S&P 500 peers. So, what does it take to help bring that kind of success to a company? She says the key to being a good director is staying committed and knowing when it's time to step down.

"It's important that if people are going to join a board that they have to be at all the board meetings; they have to be there in person; [and] put the time into the work that happens between board meetings," Cox said in a recent interview with TheStreet. "Every board member needs to make sure that they are still an active contributor because at the point where you are not it's time to move on."

In addition to leading North Carolina-based start-up, Humacyte, a regenerative medicine firm, Cox is also a long-time director to Texas Instruments (TXN) - Get Report , Celgene (CELG) - Get Report and Cardinal Health (CAH) - Get Report . Compared to the S&P 500's five-year return of 51.5%, Texas Instruments shares have seen a 60.5% rise, while Cardinal Health's stock is up 79.6%. Celgene shares have jumped 251% over five years. 

One of the things that separates Cox's service from others is that she serves on boards that also outperform when it comes to gender diversity.

Cox is one of five women sitting on the 12-person board for Texas Instruments, the Dallas-based semiconductor manufacturer. She has been a director there since 2004. At Celgene, a biotech company that makes drug therapies for cancer and inflammatory disorders, she is one of four women sitting on a board of 11 directors, and has been a director for the past seven years. Cardinal Health counts four women on its 12-person board. Cox has been a director there since 2009.

This year, gender inequality in the boardroom is in the spotlight, given that there are seven companies in the S&P 500 that have no women on their boards. The lack of gender diversity at these big companies as well as those companies that have minimal presence of diversity in the boardroom is a problem not just for women in corporate America, but for investors, too. Research shows that companies with a higher proportion of women directors tend to perform better.

Cox was one of 10 women highlighted last month by TheStreet as directors with strong resumes who can be great additions to any company's board -- especially those with no women on them.

Before she became CEO of Humacyte, Cox served as chairman of Prism Pharmaceuticals, a company that was acquired by Baxter (BAX) - Get Report in 2011. From 2003 through 2009 she was president of the global pharmaceuticals division at Schering-Plough until it merged with Merck (MRK) - Get Report in 2009.

We spoke with Cox to talk about gender diversity in the boardroom and what it takes to be an effective director. Here is an edited transcript of TheStreet's conversation with Cox.

TheStreet: Does it surprise you that there are large public companies with no women on their boards?

Carrie Cox: I would say probably not because it's been a slow process to get pretty consistent gender diversity. It needs to continue to change, but I am not surprised to hear that this hasn't completely finished changing yet.

TST: There is an increasing association of company performance to board diversity. Is this stating the obvious?

CC: There are a whole range of things that your board is tasked with doing and should be focused on. Gender diversity being an important one, but clearly one of many. If you're doing that well you are probably doing a lot of other things well, which may in fact be tied to better performance.

TST: Why should investors care about gender diversity in the boardroom?

CC: It goes far beyond the traditional role of management succession and audit committee responsibility. The more different perspectives you bring into a board, chances are [you will have a] stronger discussion or debate and ultimate outcome.

TST: What traits or skills can a woman bring to a board as well as upper management that perhaps are less obvious to a man?

CC: It's really the ability to recognize the power of a diverse group of people and build a team of people who have different perspectives, backgrounds, viewpoints, ethnic backgrounds and geographic backgrounds. The stronger you can build a team [like that], the likelihood of better performance is greater. Women can clearly be a part of that, but I don't [think it's about separating] gender specific traits.

TST: You sit on several boards -- how do you find the time for all of this and still run a company? Do you worry at times that you are spreading yourself too thin?

CC: Over the course of a career -- especially a global career -- you get very good at handling a lot of different tasks and being very efficient with your time. Here is one of the ways where having children early in life is a great way to prepare you to multitask really well.

I work really effectively on airplanes. There's no magic to it. I've never had the feeling that I was dropping the ball.

TST: There has been an increasing discussion about "overboarding." Credit Suisse had a report out recently on the topic, positing that companies where board members sit on just one board perform better. Do you agree?

CC: It's important that if people are going to join a board that they have to be at all the board meetings; they have to be there in person; [and] put the time into the work that happens between board meetings. I wouldn't say it's a specific number of boards as much as it is making sure that when you make a commitment to a board that you fulfill it in terms of all the things that that particular board needs. It's going to be different for different boards, but there is a lot of work that has to happen outside of the board room.

TST: What is it about each of these companies that intrigued you to sit on their boards -- and stay for so long?

CC: They are great companies and you will note the theme is innovation and technology. I have a real fondness and focus on health care and then in the case of TI, the technology that they practice and the innovation they bring is really impressive.

For me I also keep assessing do I continue to bring value to the board? It's clear that I continue to enjoy these boards, but I think every board member needs to make sure that they are still an active contributor because at the point where you are not it's time to move on.

TST: Now for your day job, what does Humacyte do and what is the company is doing in the area of regenerative medicine?

CC: Humacyte is a clinical stage company in biomedical engineering. We are developing products that can be used for hemodialysis access.

A patient whose kidneys begin to fail over time have to go in to have their blood cleansed ... and they need a way to enable that dialysis to take place. The current standard of care is where there is certain room for improvement. So we're trying to bring a better product forward and base it on regenerative medicine ... so that we can hopefully create a new human tissue based vessel that can be implanted into any patient. So it's very cool high-science technology.