Ask Tufts Experts: Raw vs. Roasted Nuts; Lactose in Yogurt

Which is a better choice for my health, raw nuts, or roasted?

Alice H. Lichtenstein, DSc, director of the Cardiovascular Nutrition Laboratory at the Human Nutrition Research Center on Aging (HNRCA) and executive editor of Tufts Health & Nutrition Letter, answers:

“Some nut proponents say raw are healthier than roasted, and some say the opposite. The fact is that there are pros and cons to each, and either kind is a good choice—so long as they aren’t covered in a lot of salt or sugar, and as long as they are used to replace less healthy choices.

• Nutrients: According to the USDA food database, the difference in vitamin and mineral content among oil-roasted, dry roasted, and raw cashews is so small as to be inconsequential in the context of an overall dietary pattern.
• Anti-nutrients: So-called ‘anti-nutrients’ are compounds that block the body from absorbing nutrients such as calcium and iron. Raw nuts may contain a higher level of ‘anti-nutrients’ than roasted, but the difference in absorbable nutrients will not make a significant impact in the context of an overall healthy diet.
• Microorganisms: Raw nuts have caused outbreaks of food poisoning due to Salmonella bacteria, and peanuts can harbor fungi that produce disease-causing compounds called aflatoxins. Roasting, blanching, or steaming will create enough heat to kill bacteria and roasting reduces levels of aflatoxins. (The FDA carefully monitors peanut products, and no outbreak of human illness caused by aflatoxins has been reported in the U.S. to date.)
• Carcinogens: The roasting process can cause the formation of chemicals called acrylamides. In animal studies, at high levels of intake, these compounds have been associated with kidney, ovarian, and endometrial cancers. However, these levels cannot be achieved by eating nuts.

“Nuts are a source of heart-healthy unsaturated fats, as well as fiber, vitamin E, and magnesium— which are nutrients of concern for many U.S. adults. Consuming any kind of nuts instead of refinedcarbohydrate choices like chips, pretzels, crackers, or croutons is a health-promoting choice. (See the July 2020 issue for more information.)”

Are lactose levels different between yogurts with live active cultures and those without?

Judith C. Thalheimer, RD, LDN, managing editor of Tufts Health & Nutrition Letter, answers: “Yogurt is made by fermenting milk. The fermentation process breaks down much of the lactose—the sugar naturally found in milk—into its constituents, glucose and galactose. For this reason, many people who suffer from lactose intolerance (low levels of the lactase enzyme necessary to break down lactose) find they can tolerate some yogurt. Some styles of yogurt, like Greek and Icelandic (skyr) are strained. This makes them thicker and more protein-rich than other yogurts. Straining also removes some lactose, so these yogurts may be even better tolerated.

“Live active cultures are probiotics that help maintain a healthy gut microbiome. Bacteria commonly used in yogurt, Lactobacillus bulgaricus and Streptococcus thermophilus produce their own lactase enzyme, and it has been suggested that consuming these live bacteria may help with lactose digestion.

“Some yogurt products are heat treated after fermentation. This kills most of the bacteria responsible for breaking down the milk sugars, and likely destroys any lactase enzyme they have released into the yogurt. Three small studies conducted in the early 2000s found that, while heat treated fermented milk was better tolerated by individuals with lactose intolerance than regular milk, yogurt with live cultures resulted in less severe gastrointestinal symptoms and lower breath hydrogen excretion (a test for lactose intolerance).

“If you have lactose intolerance, yogurt may still be an option for you. It is possible that yogurts with live and active cultures may have a slight edge over heat-treated products (the label will indicate if live cultures are present). Be aware that the number of live bacteria in a container of yogurt will dwindle over time. For general health, choose products with little or no added sugars, and mix in your own fresh or frozen fruit.”

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