As I noted before, I wouldn't put a lot of stock in this research effort:
1) Massive conflicts of interest.
Two were noted for this paper. Both involved non-paid affiliations:
Conflict of Interest Disclosures: Dr Salas-Salvadó has reported receiving research funding and is a nonpaid member of the scientific advisory committee of the International Nut Council. Dr Ros has reported receiving research funding and is a nonpaid member of the scientific advisory committee of the California Walnut Commission. No other disclosures were reported.
2) Olive oil is given at 140 g per day; nuts a tiny fraction of that.
HUH??? From what I can glean, olive oil was 50ml per person per day (converted to 3.381 US TBS.) Mixed nuts were 30 g per day per person.
3) The low-fat group wasn't very low-fat (despite the advice).
Agreed! In this paper, the low-fat group averaged 40.17% of calories from fat. Interestingly, the EVOO group only averaged 41.81% and the mixed nut group averaged 43.22%. In fact, the macronutrient ratios across the board for the three arms of the study were surprisingly similar. The Low fat arm: 16.7%-P/39.19%-C/40.17%-F; the EVOO arm: 17.52%-P/37.21%-C/41.81%-F; and the mixed nut arm: 16.81%-P/36.39%-C/43.22%-F.
The biggest difference that I observed between the groups was that of dietary cholesterol. The low-fat group consumed on average 327.8 mg of daily cholesterol; whereas the EVOO group averaged 365 mg and the mixed nut group came in at 364 mg. Another difference can be found in overall caloric intake. The low-fat group averaged the lowest calories at 2053 kcal. The EVOO group came in at 2144 kcal and the mixed nut group averaged 2234 kcal. Lastly, there was a difference in dietary fiber that seems to indicate the EVOO and mixed nut group may have consumed more fruits and vegetables. The low-fat group consumed 11.63 g based on 1,000kcal. The EVOO group came in at 12.44 g. The mixed nut group averaged 12.42 g.
It’s very difficult to make any case pitting macronutrient groups (such as LFHC vs. HFLC) against one another from this paper as G correctly points out; they are VERY similar. Instead, the authors surmise that the abundance of antioxidants and phenolic compounds found in EVOO and nuts may be responsible for the small, but statistically significant cognitive improvements compared to the “low-fat” arm. For anyone who’s got the paper, I find Figure 2. Changes in Cognitive Function Measured With Composites by Intervention Group to be fairly impressive. I’m unfortunately unable to copy it here, but will happily pass the paper along to anyone who wants it- just PM me your email address.
I didn’t see anything earth-shattering here, but it does point towards a trend suggesting cognitive benefit from EVOO, nuts, vegetables, and fruits...nothing new.