There is vast literature supporting the notion that the health of people consuming Western diets could improve by increasing the proportion of n-3 fatty acids such as docosahexaenoic acid (DHA) and reducing levels of arachidonic acid (AA) in their cells (1). Seafood consumption provides direct sources of DHA, which can otherwise only be produced in small amounts by humans from plant-based ALA-rich oils in the diet. Attempts to increase tissue DHA in humans by raising dietary ALA have had limited success, partly because dietary LA, the progenitor of AA, suppresses DHA synthesis and accumulation. Using a rat model, this work aimed to determine the degree to which altering the proportion of dietary LA to ALA could enhance tissue DHA accumulation. Blends of natural oils were used to derive 54 diets (n = 5 per group) covering three total fat levels: 11.8 en%, 22.2 en%, and 39.4 en%. Seven levels of polyunsaturated fatty acids (PUFA) were tested, ranging from 2% to 45% of dietary fat, with LA:ALA ratios of 10:1, 5:1, 2:1, 1:1, and 0.5:1(2). Phospholipid fatty acids isolated from liver, heart, brain, skin, lung, muscle, red blood cells, and plasma were measured, with particular focus on n-3 long-chain PUFA. Across the wide array of diets, saturated fatty acids remained relatively stable in all tissues. This contrasted with the type of PUFA in tissues; for example, n-6 fatty acids increased as the LA:ALA ratio rose, whereas tissue n-3 fatty acids increased as LA:ALA ratio declined. This influence of dietary PUFA content on n-6 and n-3 levels was strongest in animals fed the lowest-fat diet, but less apparent at higher fat intakes. At all fat intakes, tissue n-3 and n-6 fatty acid levels were driven mainly by the dietary LA:ALA ratio. The highest tissue DHA was obtained at ratios of 1:1 or lower, whereas the highest LA:ALA ratios produced the greatest AA levels at the expense of DHA. The largest DHA increases occurred in liver, rising from 6% to 16% of total fatty acids, followed by heart (4% to 14%), plasma (2% to 8%), and brain (15% to 21%). In contrast, AA decreased across the same diets in liver (28% to 7%), heart (26% to 13%), plasma (15% to 5%), and brain (11% to 9%). These findings verify that adjusting the dietary balance of LA and ALA using vegetable oils alone could improve n-3 status across all tissues, including raising DHA to comparable levels reported for similar animals fed with fish oils (3). Together with data from populations consuming largely vegetarian diets (4), the results suggest that enriching the basal fats in Western diets towards higher ALA could improve n-3 fatty acid status while reducing pressure on marine resources.