Here's a question I get a lot: "I want to own McDonald's because it's a Warren Buffett type business with a great moat, but doesn't the bacon kill it?"

Great question. And the answer is more nuanced than "no bacon allowed in the portfolio." The pork revenue at McDonald's is real, but it's a small enough share of total revenue that McDonald's usually passes the 5 percent non-permissible income threshold. The real screening issue is something else entirely: the balance sheet, and sometimes the alcohol at Yum Brands' sit-down concepts.

Let me actually walk through the specific chains and show you the math.

McDonald's Corporation (NYSE: MCD)

McDonald's operates roughly 40,000 restaurants globally. The company's business model is heavily franchised. Only about 5 percent of restaurants are company-owned; the rest are operated by franchisees who pay rent and royalties to the parent.

Core business: Quick-service restaurant operator and franchisor. Permissible sector.

Pork exposure: McDonald's sells bacon-based items (McBacon, bacon McDouble, bacon options on burgers, sausage McMuffins). Pork is also a component of some sauces and prepared foods. Industry estimates put pork product revenue at around 3 to 5 percent of total system sales, depending on market. In Muslim-majority markets, McDonald's sources halal-certified meat and typically doesn't serve pork at all.

The franchise math matters: Most of McDonald's revenue is rent and royalties from franchisees, not food sales. The pork exposure at the parent-company level is actually smaller than at the restaurant level because McDonald's doesn't collect per-product revenue.

Non-permissible income: Pork-related revenue plus small amounts of interest income typically puts McDonald's at around 2 to 4 percent of total revenue. Passes the 5 percent threshold in most years.

Debt-to-market-cap: Long-term debt around $38 billion against a market cap of ~$215 billion. Ratio about 18 percent. Passes.

Cash and interest-bearing securities: Low relative to market cap. Passes.

Receivables: Passes.

Result: McDonald's typically passes Shariah screening. Muslim investors should purify the portion of dividends attributable to pork and other non-permissible income (usually around 3 to 4 percent of dividends received).

Worth noting: some scholars take a more conservative view that selling pork at all, even as a small fraction of revenue, should disqualify a company. That's a minority position among screening bodies. Mainstream methodology (AAOIFI, DJIM, S&P Shariah) uses the 5 percent tolerance and McDonald's clears it.

Yum! Brands (NYSE: YUM)

Yum operates KFC, Pizza Hut, and Taco Bell globally. After spinning off Yum China in 2016, Yum is primarily a franchisor of these three brands outside China.

Core business: Franchisor of fast food brands. Permissible sector.

Pork exposure: Pizza Hut sells pepperoni and bacon. KFC's product is chicken (halal or not depending on market). Taco Bell sells beef and chicken primarily. Overall pork exposure is smaller than McDonald's at ~2 to 3 percent.

Alcohol exposure: Some Pizza Hut locations and some international KFC locations serve alcohol. Small percentage of total revenue.

Non-permissible income: Combined pork, alcohol, and interest income is typically under 5 percent. Passes.

Debt-to-market-cap: This is Yum's problem. Yum has historically operated with very high use and low equity after refinancing and share buybacks. Long-term debt around $12 billion. Market cap around $38 billion. Debt ratio about 32 percent. Above the 30 percent threshold. Borderline to fail.

Result: Yum is borderline on the debt ratio. In some years it passes, in others it fails. Check current figures before buying.

Yum China (NYSE: YUMC)

Yum China operates KFC, Pizza Hut, and smaller brands in mainland China. It's the largest restaurant operator in China.

Core business: Quick-service and casual dining in China. Permissible.

Pork and alcohol exposure: Yum China has meaningful alcohol revenue from Pizza Hut casual dining locations in China. Pork is used in some menu items. Combined non-permissible income can be around 4 to 6 percent. Borderline.

Debt-to-market-cap: Lower than US parent. Around 20 percent. Passes.

Result: Borderline on non-permissible income. Check current breakdown.

Chipotle Mexican Grill (NYSE: CMG)

Core business: Fast-casual Mexican food. Permissible.

Pork exposure: Chipotle serves carnitas (pork) as one of its four protein options. Industry estimates suggest carnitas is the least-ordered protein at Chipotle, accounting for around 5 to 7 percent of entree selections. That translates to maybe 3 to 5 percent of revenue.

Alcohol exposure: Very limited. Only some restaurants serve beer or margaritas, and the revenue share is negligible.

Non-permissible income: Typically at or just under 5 percent. Borderline.

Debt-to-market-cap: Chipotle has a very clean balance sheet. Very little long-term debt. Market cap ~$75 billion. Debt ratio very low. Passes easily.

Cash ratio: Chipotle holds around $1 billion in cash. Low ratio. Passes.

Result: Chipotle usually passes Shariah screening. Borderline on the pork-related revenue, so check the current breakdown.

Starbucks (NASDAQ: SBUX)

Core business: Specialty coffee and beverage retailer. Permissible sector.

Pork and alcohol exposure: Starbucks sells some breakfast items with bacon or sausage. Revenue share is small (~2 percent). Some Starbucks locations in Europe and Asia serve wine and beer in the "Starbucks Reserve" format, but this is a tiny percentage of overall revenue.

Non-permissible income: Under 3 percent. Passes.

Debt-to-market-cap: Long-term debt around $14 billion. Market cap ~$115 billion. Debt ratio about 12 percent. Passes.

Result: Starbucks typically passes Shariah screening comfortably.

Domino's Pizza (NYSE: DPZ)

Core business: Pizza delivery and franchising. Permissible.

Pork exposure: Pepperoni, Italian sausage, bacon, ham. Pork-related toppings make up a meaningful share of pizza revenue. Industry estimates put pork product revenue at around 10 to 15 percent of Domino's sales.

Non-permissible income: Around 10 to 15 percent. Fails the 5 percent threshold.

Debt-to-market-cap: Domino's has very high use. Long-term debt around $5 billion. Market cap ~$16 billion. Debt ratio about 31 percent. Also fails debt threshold.

Result: Domino's fails Shariah screening on both pork revenue and debt ratio. This is a definite no.

Papa John's (NASDAQ: PZZA)

Same pork exposure as Domino's, also fails on non-permissible income.

Wendy's (NASDAQ: WEN)

Core business: Burger quick-service. Permissible.

Pork exposure: Bacon in multiple menu items, sausage in breakfast. Estimated 4 to 5 percent of revenue.

Debt-to-market-cap: Wendy's has high use. Around 65 percent. Fails debt ratio.

Result: Fails on debt.

Restaurant Brands International (NYSE: QSR)

Owns Burger King, Tim Hortons, Popeyes, and Firehouse Subs. Franchise-focused model similar to Yum.

Pork exposure: Bacon burgers, bacon breakfast items, pork sausage. Similar to McDonald's at ~3 to 5 percent.

Alcohol exposure: Burger King doesn't serve alcohol in most markets. Negligible.

Debt-to-market-cap: RBI has historically had very high use due to the 3G Capital acquisition model. Long-term debt around $13 billion against a market cap of ~$30 billion. Debt ratio about 43 percent. Fails.

Result: Fails on debt ratio.

Darden Restaurants (NYSE: DRI)

Owns Olive Garden, LongHorn Steakhouse, Capital Grille, Yard House, and other casual dining brands.

Core business: Casual dining. Permissible.

Alcohol exposure: This is the big issue for Darden. Its brands are full-service restaurants that serve alcohol extensively. Olive Garden's wine revenue alone is substantial. Industry estimates put alcohol revenue at 10 to 15 percent of total sales for Darden.

Pork exposure: Additional non-permissible revenue from pork products.

Non-permissible income: Well over 10 percent. Fails.

Result: Fails on non-permissible income.

Texas Roadhouse (NASDAQ: TXRH)

Core business: Casual dining steakhouse. Permissible.

Alcohol exposure: Significant. Bar sales at casual dining chains are meaningful revenue.

Non-permissible income: Probably 8 to 12 percent depending on mix. Fails.

Result: Fails.

Chick-fil-A

Private company. Not available for public investment. But since people ask: Chick-fil-A doesn't serve pork products or alcohol in its restaurants. It would almost certainly pass sector and non-permissible income screens if it were public. But since it's privately held and controlled by the Cathy family, this is moot for retail investors.

The pattern for fast food

Fast food chains roughly divide into three groups:

1. Pass the screen usually: McDonald's, Starbucks, Chipotle (borderline). Mostly because they're franchise-heavy or coffee/beverage-focused with manageable pork exposure.

2. Borderline or fail on balance sheet: Yum Brands, RBI. Typically permissible sector and acceptable non-permissible income, but debt ratios are high.

3. Fail on non-permissible income: Domino's, Papa John's (pork-heavy), Darden, Texas Roadhouse (alcohol-heavy).

Dividend purification

For names that pass screening but have some non-permissible income (McDonald's, Starbucks, Chipotle), you should purify the portion of dividends attributable to the non-permissible revenue. For McDonald's, that's typically around 3 to 4 percent of dividends. For Starbucks, about 2 percent. For Chipotle, closer to 5 percent.

The bottom line

Fast food chains are not universally non-compliant. Pork exposure is real but usually under the 5 percent tolerance threshold for chains with diversified menus. The bigger screening problem for the sector is either high use (Yum, RBI, Wendy's) or heavy alcohol revenue at sit-down chains (Darden, Texas Roadhouse).

McDonald's and Starbucks are the cleanest large fast food names. Chipotle is borderline on pork. Domino's and Papa John's fail on pork. Darden fails on alcohol. Yum Brands is borderline on debt.

Run whatever you're considering through FaithScreener to get the specific current-year figures. The answer in this sector really does depend on the numbers in a given year because balance sheets and revenue mix shift.

Fast Food Chains: McDonald's, Yum Brands, and Pork-Based Menu Items