The U.S. economy is looking strong, and that sent the stock market sharply higher on Thursday. As of 3 p.m. EDT, several indexes were at or near all-time highs, with the Dow Jones Industrial Average (^DJI 0.23%) climbing 264 points to 33,995. The S&P 500 (^GSPC 0.80%) had gained 42 points to 4,167, and the Nasdaq Composite (^IXIC 1.14%) was up 164 points to 14,022.

Up-and-coming disruptive stocks have gotten a lot of headlines lately, but don't count out some of the oldest and best-established blue chip companies in the stock market. Today, both UnitedHealth Group (UNH -0.83%) and PepsiCo (PEP -0.45%) gave investors their latest results, and both businesses look like they have the staying power to keep growing well into the future.

Fit as a fiddle

Shares of UnitedHealth climbed more than 3%, making it the biggest gainer in the Dow. The health insurance giant posted strong first-quarter financial results that pointed to just how solid the fundamentals of the healthcare industry are right now.

Stethoscope, calculator, pen, and insurance benefits paper.

Image source: Getty Images.

UnitedHealth's numbers were impressive. Revenue moved higher by 9%, with gains at both the UnitedHealthcare insurance segment and the Optum healthcare services business. Operating earnings jumped 35% year over year, and that supported a 43% gain in adjusted earnings, which came in at $5.31 per share.

Moreover, 2021 is going better than UnitedHealth originally expected, and so management boosted its guidance for 2021. The company now sees adjusted earnings coming in between $18.10 and $18.60 per share, and that figure includes roughly $1.80 per share in added costs due to impacts from the COVID-19 pandemic. If efforts to fight the pandemic prove successful, then presumably it should result in even better earnings in 2022 and beyond.

UnitedHealth's balanced business approach includes both traditional health insurance and the variety of services and information that the Optum units provide, and it has paid off well over the long run. As conditions get closer to normal, UnitedHealth's business should have even more tailwinds in its favor.

A small pop for PepsiCo

Elsewhere, PepsiCo shares were up less than 1%. However, the snack and beverage company's financial results were stronger than that small move would suggest.

Even with the ongoing challenges of the pandemic, PepsiCo did well in the first quarter of 2021. Revenue was up nearly 7% year over year, and that helped push earnings per share higher by 29% to $1.24. Some of those gains came from acquisitions and other structural changes within PepsiCo's corporate family, particularly in international markets. However, organic growth of 2% systemwide was reasonably good, coming largely from unit volume growth of 1% in food and snacks and 2% in beverages.

PepsiCo also indicated it still anticipated solid performance throughout 2021. Its guidance includes calls for mid-single-digit percentage increases in organic sales, with slightly faster growth in core earnings. PepsiCo remains committed to returning capital to shareholders, mostly through dividend payments and to a smaller extent by way of modest stock repurchase plans.

Investors have been pleased to see PepsiCo take market share away from its key rivals in both the beverage and the snack areas. If those trends persist, then they could help PepsiCo's stock continue to move higher.