Assessing the nutrient intake of a low-carbohydrate, high-fat (LCHF) diet: a hypothetical case study design

This week’s research paper is from Auckland dietician Caryn Zinn and two colleagues and was published in the journal BMJ Open. You can click the heading for the pdf version of this paper.

In the article, Zinn and colleagues look at the nutrient content of the typical low carbohydrate healthy fat (LCHF) diet. One of the criticisms of the diet in nutrition circles is that it is devoid of nutrients and has a higher saturated fat content than is recommended in the dietary guidelines. The "saturated fat is the cause of heart disease” hypotheses or as it is more widely known the “diet-heart hypothesis” has been increasingly challenged in the last couple of years with a number of review papers (systematic reviews and meta-analysies) showing the lack of association between iontake of satiurated fat and cardiovascular disease. The PURE study published last year in the Lancet was the latest nail in the coffin of the diet-heart hypothesis. So the fact that the LCHF diet exceeded the saturated far guidelines is probably not an issue any more.

Back to the nutrient content. 

In this study the researchers calculated nutrient contents for two typical LCHF diets, one male and one female. The diets chosen were not very low carb or ketogenic, but rather around the 130 gm of carbs per day defined as the upper limit of “low carb”. The two diets reached adequate levels of all nutrients as defined by the Australian/New Zealand nutrient reference value (NRV) thresholds except for iron in the female where the iron levels were 86-98% of the RDI values.

One particularly interesting area in the Omega 6:Omega 3 ratio. Historically this ratio was thought to have been 1:1, but in recent years with the dramatically increased use of seed (vegetable) oils in cooking and processed foods this ratio in the so-called average Western diet or Standard American diet (SAD) has blown out to level around 15-20:1. These two diets had ratios of 3.5:1 (female) and 2.2:1 (male) - a massive improvement from the modern diet.

The article shows clearly that nutrient deficiency is not an issue with LCHF diets.