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Artificial intelligence has helped push major indexes to fresh highs. But according to Jim Cramer (1), that momentum may be exactly why investors should start looking elsewhere.

The AI rally has also become increasingly concentrated, with the 10 largest companies now accounting for roughly 40% of the S&P 500, according to RBC Wealth Management (2).

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With both the S&P 500 and Nasdaq Composite climbing, Cramer is warning that some of the biggest winners (especially in tech) could be vulnerable to a pullback after such a strong run. His takeaway is simple: portfolios that lean too heavily on one trend can quickly get exposed if sentiment shifts.

Instead, he's pointing to a part of the market that's been largely ignored.

Cramer calls health care the "cold" side of the market (3) — not because the fundamentals are weak, but because investor enthusiasm has cooled. That disconnect is exactly what makes it appealing.

While tech stocks tied to AI have surged, many health care names have lagged or even declined. In one recent quarter, health care fell more than 7% while technology gained over 20%, according to investment reports using S&P Dow Jones Indices data (4).

This gap is what Cramer sees as an opportunity for investors looking to rebalance.

He highlighted four companies in particular (5):

CVS Health (NYSE: CVS)

Cardinal Health (NYSE: CAH)

Johnson & Johnson (NYSE: JNJ)

UnitedHealth Group (NYSE: UNH)

Each offers a different way to gain exposure to the sector from insurance and retail pharmacies to drug distribution and pharmaceutical development.

For example, Cramer argues CVS could benefit as competitors shrink or disappear, while Cardinal Health is expanding into higher-growth services beyond its traditional distribution business.

Meanwhile, he says Johnson & Johnson's drug pipeline and UnitedHealth's scale and earnings strength give them staying power even if broader market conditions shift.

The common thread is that these companies aren't riding the AI wave, which may be exactly why they could help cushion portfolios if that wave loses momentum.

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Cramer's advice centers on diversification: a principle that's easy to overlook during a bull run.

When one sector dominates headlines and delivers outsized returns, it's tempting to keep piling in. But that can leave investors overly exposed if the trend reverses.

Adding positions in sectors that behave differently like health care can help smooth out volatility over time. That doesn't mean abandoning tech or AI altogether. Instead, it's about reducing concentration risk.

For everyday investors, that could look like:

Trimming positions that have run up significantly

Reinvesting gains into underperforming sectors

Broadening exposure across industries, not just themes

Health care in particular tends to be less sensitive to economic cycles than other sectors. People still need medical care regardless of whether the economy is booming or slowing, which can make the sector more defensive during downturns.

The bigger message behind Cramer's call isn't just about health care, it's about timing. Markets move in cycles, and today's top performers aren't always tomorrow's winners.

After a powerful rally driven by AI enthusiasm, even a modest shift in sentiment could lead to volatility in tech-heavy portfolios. That's where balance comes in.

By pairing high-growth investments with more stable, overlooked sectors, investors may be better positioned to handle whatever comes next, whether the AI rally continues or starts to cool.

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CNBC (1),(3),(5); RBC Wealth Management (2); Simmons Bank (4)

This article originally appeared on Moneywise.com under the title: Jim Cramer says health care is the 'cold' hedge your AI-heavy portfolio is missing — and shares 4 stocks to consider

This article provides information only and should not be construed as advice. It is provided without warranty of any kind.