As you get older, it's generally a good rule of thumb to start lowering your portfolio's risk profile. But that doesn't mean you should swap out all of your stocks for lower-risk investing vehicles like CDs or bonds. There are a fair number of low-risk stocks, after all, that offer outstanding growth prospects.

Armed with this insight, we asked three of our contributors which stocks they think might be suitable investing vechicles for senior citizens. They recommended Celgene (NASDAQ:CELG), Nucor (NYSE:NUE), and Cardinal Health (NYSE:CAH). Here's why. 

An elderly man and woman sitting back to back.

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This biotech offers unusual levels of growth with far less risk than you'd expect

George Budwell (Celgene): The large-cap biotech stock Celgene probably isn't even on your radar if you're a senior citizen. After all, this company operates in a particularly high-risk industry (biopharmaceuticals), and its stock can hardly be construed as a value play at present; Celgene's shares are currently trading at a price-to-sales ratio of 8.8 and a sky-high price-to-earnings ratio of 51.

But there's a lot more than meets the eye with this top biotech stock.

First off, Celgene's 20%-plus compound annual growth rate (CAGR) for its top line over the past three consecutive years makes it one of the fastest-growing companies in the world. Most importantly, though, this astonishing level of growth isn't expected to taper off in a significant manner until the mid-2020s at the earliest.

The commercial launch of its latest blockbuster drug, Otezla -- which is indicated for psoriatic arthritis and plaque psoriasis -- is still in the early stages of its commercial launch, and the company's blockbuster-in-waiting ozanimod is successfully winding its way through a late-stage clinical program for relapsing multiple sclerosis and ulcerative colitis.   

The point is that Celgene's ultra-high growth appears to be sustainable for the next five to seven years minimum -- meaning that its shares are actually much cheaper than they may first appear. And barring any black swan-type of events, this biotech stock is arguably a fairly safe bet, given its strong track record of steadily growing its footprint in the high-value oncology and inflammatory disease drug markets. 

A Trump play that looks fairly undervalued

Neha Chamaria (Nucor): A highly cyclical steel stock may not seem to be the best fit for a senior citizen's portfolio, but Nucor's at a stage where its growth prospects outweigh its challenges, making it a great stock to consider.

Before anything else, knowing that Nucor has increased its dividend for 44 straight years and has found a place in the elite Dividend Aristocrat list proves that the company is run well enough to navigate business cycles and reward shareholders. That itself should encourage any person in their golden years to have Nucor on their radar. What's particularly encouraging is that Nucor's investment thesis has improved considerably in recent months.

The steel sector is visibly springing back to life after a long period of lull. With Beijing confirming its plans to cut steel capacity, steel players are hoping for an improved demand-and-supply situation to boost steel prices further. Most importantly, if President Donald Trump keeps his word and kick-starts spending on infrastructure, Nucor could be a major beneficiary thanks to its dominant position in the U.S. steel industry.

Of course, Nucor shares have already rallied substantially since the presidential election, but the stock has lost a bit of momentum lately and looks like a great value play right now given its growth potential.

First, at a trailing price-to-earnings ratio of about 24, Nucor is trading substantially below the industry average P/E. Second, analysts expect Nucor to deliver exceptional growth in earnings per share this year, as evidenced by its forward P/E of only around 16 times. Third and most important, Nucor generated nearly 1.3 times its net income in free cash flow, coming in at around $1.1 billion during the trailing 12 months. A strong financial footing is a must for any stock that retirees may want to own. The stock is changing hands at around 17 times its FCF, which isn't pricey at all. Factor in a dividend yield of 2.5%, and Nucor looks like a great value stock that senior citizens may want to consider today.

A healthcare titan whose services continue to be in demand

Chuck Saletta (Cardinal Health): Cardinal Health is one of the largest healthcare distribution and services companies in the world. Many of its services are focused on efficiency, and thus they will remain in demand as we search for lower-cost ways to deliver healthcare. Despite the recent run-up in its stock price, its shares remain attractively priced today and could find a home in the stock portion of a senior's portfolio.

Cardinal Health takes care of its investors with a solid balance sheet. It carries a debt-to-equity ratio around 0.85, a current ratio around 1.1, and has over $1.8 billion in cash available to it. That balance sheet indicates that while the company does use debt, it hasn't overleveraged itself, and it looks capable of handling a typical economic stumble. It also suggests that Cardinal Health is not at a substantial risk of running into trouble paying off or financing its debt at any time in the near future.

The balance sheet should help investors sleep at night. What makes Cardinal Health a value, however, is the fact that its shares are trading below what I view as a fair value for its business based on its proven results and expected growth rate. Based on a discounted cash flow model, I recently estimated Cardinal Health to be worth $29.0 billion, a bit above the $25.9 billion where its shares recently traded hands.

As if that weren't enough of a reason to own its shares, Cardinal Health rewards its shareholders with a dividend that it has regularly increased. With a payout ratio of around 42% of earnings, it has room to continue increasing that dividend over time as its business continues to grow.

Put it all together, and Cardinal Health has what it takes to be a value stock worthy of consideration for the stock portion of a senior's portfolio.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.