• Low carb diets favouring animal-derived protein and fat sources were associated with higher mortality rates, the study says. (Photolibrary RM/Getty Images)Source: Photolibrary RM/Getty Images
"Animal-based low carbohydrate diets should be discouraged.”
By
Yasmin Noone

17 Aug 2018 - 8:30 AM  UPDATED 17 Aug 2018 - 8:32 AM

A new study published in The Lancet Public Health journal today reveals potential bad news for people who’ve been following a particular kind of low-carb diet.

If your low-carbohydrate eating pattern sees you replacing a lot of carbohydrate rich foods for a high quantity of animal-based proteins, you may be unknowingly shortening your life span.

“Our findings suggest a negative long-term association between life expectancy and both low carbohydrate and high carbohydrate diets when food sources are not taken into account,” the study states.  

“These data also provide further evidence that animal-based low carbohydrate diets should be discouraged.”

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It sounds harsh, especially given that low carbohydrate diets can help you to lose weight in the short-term and improve your cardio-metabolic risk.

But there is a silver lining. The international research shows that your mortality risk could be lowered if you follow a low-carb diet featuring plant-based proteins and fat.

“These data also provide further evidence that animal-based low carbohydrate diets should be discouraged.”

“Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality,” the study reads.

“Whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality.”

The research also linked diets both low and high in carbohydrates to an increase in mortality, while those who ate moderate amounts of carbs fared best.

“Both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50–55 per cent carbohydrate intake.”

The results showed that from age 50, the average life expectancy for those with moderate carbohydrate intake was four years longer than those with very low carbohydrate consumption and one year longer compared to those with high carbohydrate consumption.

The observational study looked at the diets of more than 15,400 people aged 45-64 years from diverse socioeconomic backgrounds in the USA over six years. Male participants reported consumed 600-4200 kilocalories (kcal) per day and female volunteers ate 500-3600 kcal per day.

The results showed that from age 50, the average life expectancy for those with moderate carbohydrate intake was four years longer than those with very low carbohydrate consumption and one year longer compared to those with high carbohydrate consumption.

To confirm these results, the researchers went one step further. They conducted a meta-analysis of studies on carbohydrate intake including more than 432,000 people from over 20 countries throughout North America, Europe and Asia.

The analysis revealed similar trends, as participants whose overall diets were high and low in carbohydrates had a shorter life expectancy than those with a moderate consumption of carbs.

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Words of carb caution

The study’s authors conclude that the best long-term approach to promote healthy ageing is to replace carbs with plant-based fats and protein when you’re on a low-carb diet.

However, the study’s findings are observational associations that don’t prove cause and effect.

The research may also generalise the diets of some Asian cultures, like the Japanese whose primary meat source may be fish – the authors acknowledge that fish could be a healthier choice than other animal proteins like beef, pork and fowl.

“On the other end of the spectrum, high carbohydrate diets, which are common in Asian and less economically advantaged nations, tend to be high in refined carbohydrates, such as white rice."

The authors also have no evidence to determine why there’s a link between mortality risk and some low-carb diets. However, they speculate that having a low-carb diet over the long-term featuring a greater amount of animal fats and proteins and a lower intake of whole-grains, fruits and vegetables could “stimulate inflammatory pathways, biological ageing, and oxidative stress”.

“On the other end of the spectrum, high carbohydrate diets, which are common in Asian and less economically advantaged nations, tend to be high in refined carbohydrates, such as white rice,” the study says.

“These types of diets might reflect poor food quality and confer a chronically high glycaemic load that can lead to negative metabolic consequences.”

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