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Investors in their 50s still have some time before retirement, but preservation of capital becomes increasingly important as the years pass. Having a risky bet go south may not be a big deal for younger investors, who have decades left in their working lives, but for investors in their 50s, a big loss could negatively affect retirement.

There's still room for taking some risk, of course, but safety should be a major concern. With that in mind, three of our Foolish contributors have found a few stocks that may make sense for investors in their 50s.  

Jason Hall: The steel industry has been hammered (Pun? Sorry.) over the past year-plus:

NUE Chart

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Iron and steel prices globally have tanked, and much in the same way that oil prices have: too much product; too little demand. This situation has led to a number of different reactions, including some illegal ones by some state-owned steel industries in some parts of the world being propped up by their governments. The U.S. government implemented tariffs in 2014, but illegally subsidized steel continues to get imported into the U.S. at prices that some steelmakers just can't compete with. 

And while this sounds like a terrible environment to invest in steelmakers, I think it makes for a good opportunity if you invest in the right steelmakers, such as Nucor Corporation (NUE 1.81%) and Steel Dynamics (STLD 2.39%). 

What makes these two steelmakers exceptions? Their operations are better suited for the ups and downs of the cyclical steel industry, with steel mills and foundries which are much more scalable to meet fluctuations in demand. By having a more variable capital and operating structure, the companies have lower fixed costs that are hugely beneficial in downturns.  

Second, both companies are well run by management teams that focus on operations and maintaining strong balance sheets:

NUE Cash and Equivalents (Quarterly) Chart

NUE Cash and Equivalents (Quarterly) data by YCharts

Bottom line: Steelmaking is ugly today, but it will recover. Nucor and Steel Dynamics will navigate the downturn just fine and be huge winners when things eventually turn for the better. 

Tim Green: Finding a balance between growth potential and preservation of capital is important for investors in their 50s. High-flying growth stocks may be fine for younger investors, but big losses need to be avoided for those in the final stages of their working lives. I think one of the best options for investors in their 50s is Berkshire Hathaway (BRK.A -0.30%) (BRK.B -0.26%), a conglomerate with an unparalleled track record headed by legendary investor Warren Buffett.

Berkshire consists of dozens of separate businesses spanning a broad swath of industries, as well as an investment portfolio valued at over $100 billion. The company generated nearly $200 billion in revenue and about $20 billion in net income in 2014, making Berkshire one of the largest companies in world measured by either revenue or profit.

From 1965 through 2014, Berkshire's per-share book value has grown at a compound annual growth rate of 19.4%, while its per-share market value has grown at a faster 21.6% annual rate. For comparison, the S&P 500 index, including dividends, has grown by only 9.9% annually. While past performance doesn't guarantee future performance, Berkshire's track record is impressive.

Buffett won't be around forever, but Berkshire is positioned well for the future. The company's businesses include Berkshire Hathaway Energy, which operates a variety of energy companies, Burlington Northern Santa Fe Railway, one of the largest railroads in North America, various insurance companies such as Geico and General Re, and dozens of other companies big and small. Berkshire buys companies that have built sustainable competitive advantages, ensuring that they generate ample cash for Berkshire to invest for decades to come.

George Budwell: When buying stocks in your 50s, I think it's important to try to avoid any major risks by focusing on companies with solid balance sheets, top-notch management, and a strong competitive edge. In my view, the mid-cap biotech stock BioMarin (BMRN -9.90%) fits that description nicely. 
 
BioMarin is quickly becoming a leader in the field of drugs for rare diseases, also known as "orphan drugs." Orphan drugs have turned into an extremely important part of the pharma industry because they offer their manufacturers extended periods of exclusivity, premium pricing structures, and tax benefits, and they tend to face little to no competition once they hit the market. And perhaps the best part is that their prices, despite being some of the highest on average among all branded medicines, haven't attracted much attention from payers because of their small target markets.    
 
Turning to BioMarin in particular, this orphan-drug specialist has been able to deliver a CAGR in terms of total revenue of an astonishing 42.5% over the past decade because of management's keen ability to garner marketing approvals for three major orphan drugs. And according to S&P Capital IQ, the Street thinks BioMarin's top line should continue this upward trend by growing another 30% next year, mainly because of the strong sales momentum of its relatively new Morquio A syndrome treatment Vimizim.
 
Perhaps most impressively, BioMarin has been able to deliver this eye-popping level of growth without stressing its balance sheet through gigantic mergers and acquisitions. The company's debt-to-equity ratio, for instance, currently stands at a hair under 30% -- well below the industry average of nearly 65%. Therefore, BioMarin appears, to me, to be a high-growth biotech stock that's built to deliver market-beating results for the long term.