The patience to invest over the long, long run is one of the factors that differentiate a good investor from a great investor. But doing so carries its own risks, as trying to predict the future can be a fool's errand.

However, your inability to predict the future shouldn't prevent you from making educated guesses about where things are headed. And indeed, this is the essence of great long-term investing. In this column, I'll make such a guess about three stocks that I see as set to profit over the next 100 years.

Profiting from global growth
Absent a world war or an environmental catastrophe (at which point your investments won't matter much anyway), it appears that the world's population will continue to grow throughout the 21st century. Just the other day, we exceeded the 7 billion mark, not bad when you consider that the world's population was only about 1.65 billion in 1900.

So how do you profit from this as an investor, as there's no such thing as a futures contract for population growth?

The agricultural option
One way is to invest in agricultural commodities. More people mean more demand for necessities like food and clothing. Take corn, for example. As you can see in the chart below, both the amount of corn produced and its price have increased markedly over the past 50 years. Assuming the population continues to grow, this is bound to continue.

Source: USDA feed grains database.

If you don't want to buy a farm or trade commodity futures, the best way to profit from a continued increase in agricultural commodity prices is to invest in companies that have exposure to these trends.

Deere (NYSE: DE) provides a great example. As the company noted in its most recent monthly sales presentation, agricultural output must double by 2050 to feed the increasingly large and rich global population. To do this, farmers will need to buy equipment, and lots of it, which they'll be able to afford given higher commodity prices. And as they say, "nothing runs like a Deere."

While I think Deere is a solid company, the one I'd go with is Monsanto (NYSE: MON). Yes, its genetically modified corn may take over the world someday. But don't you want a piece of that action? Its innovative approach and genetically modified seeds are increasing farm yields around the world and making the company loads of money. Since 2001, both its sales and net profit margin have more than doubled. And it earned almost $3 per share in the past 12 months, which is more than five times its 2001 earnings per share of $0.57.

The energy option
If agricultural commodities aren't your thing, a second option is to invest in energy. Like corn, both the demand for and price of energy have risen consistently over the past decades. Emerging countries such as Brazil, India, and China have increased their energy consumption by 83%, 95%, and 243%, respectively over the past 40 years. And at least with respect to oil, as my colleague Alex Planes recently noted, the era of cheap energy is gone.

Source: Indexmundi.com.

The safest bet in the energy sector is to go with a major integrated oil and gas producer such as ExxonMobil (NYSE: XOM), Chevron (NYSE: CVX), or ConocoPhillips (NYSE: COP). Even though these companies have enormous balance sheets, they've shown a remarkable ability to grow. In just the past year, for example, Exxon's total revenue increased from $92.4 billion in the third quarter of 2010 to more than $125 billion in the third quarter of this year, due in large part to higher energy prices. Chevron and ConocoPhillips show similar growth patterns.

The health-care option
Another way to profit from the growing global population is to invest in companies with exposure to health care. Decreasing fertility rates and increasing life expectancies are resulting in older populations throughout the developed world. The number of Americans aged 60 to 64 jumped from 11 million to 17 million in the most recent census. There are similar trends in places like Germany, Japan, South Korea, and Spain, just to name a few.

While you could play it safe with a large health insurance company like Aetna (NYSE: AET), with its roughly 35 million customers, I prefer the smaller medical device manufacturing company Intuitive Surgical (Nasdaq: ISRG). Known for its da Vinci surgical system, Intuitive Surgical has experienced impressive growth over the past few years. Since 2001, its annual sales have gone from $51.7 million to $1.65 billion, and the company has gone from a loss of $16.7 million in 2001 to a profit of $465 million over the past 12 months.

The bottom line
While investing is partially a blind bet on the future, using large macroeconomic trends like the ones discussed in this column can anchor your portfolio to the unerring progress of the human race. For other solid investment advice, check out the free report we recently issued about 11 rock-solid dividend stocks recommended by our analysts here at The Motley Fool. Click here to access it while it's still free and available.